Development With A Dot

Blog on development in general, and specifically on .NET

  • Entity Framework Pitfalls: Collections of Types Other Than ICollection<T> Are Ignored

    If you expose in your entity a collection of a type other than ICollection<T> (or one inheriting from it, such as IList<T>) then it will be ignored. This is a bit absurd, because you might want to expose a collection as read only, where you would probably use IEnumerable<T>. For the record, NHibernate allows that.

    A possible solution is to have a non-public field of type ICollection<T> and to expose it as an IEnumerable<T> property. The problem is that you won’t be able to use the property in LINQ queries, because it is not mapped. And conventions won’t help either, because you cannot configure collections there.

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  • NHibernate Pitfalls: HQL Queries With Joins

    This is part of a series of posts about NHibernate Pitfalls. See the entire collection here.

    Normally, in an HQL query, you can omit the select clause, that is, the two queries are identical:

       1: var q1 = session.CreateQuery("from Product"); //both return IList<Product>
       2: var q2 = session.CreateQuery("select p from Product p");

    However, if you add joins, then it’s a whole different matter:

       1: var q3 = session.CreateQuery("from Product p left join p.OrderDetails");             //returns IList<Object[]>
       2: var q4 = session.CreateQuery("select p from Product p left join p.OrderDetails");    //returns IList<Product>
       3:  

    Worse, queries q3 and q4 will not filter distinct root entities, meaning, you will get the cartesian product of Product x OrderDetail.

    So, you will need to select the root entity (select p), plus add a distinct entity result transformer (Transformers.DistinctRootEntity) to get what you want:

       1: var q5 = session.CreateQuery("select p from Product p left join p.OrderDetails").SetResultTransformer(Transformers.DistinctRootEntity);    //IList<Product>

    This doesn’t happen with LINQ, it always performs a distinct root entity selection, but it also happens with Criteria and QueryOver.

    Thanks to Alexander Zaytsev (@hazzik) who reminded me of this!







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  • Lesser-Known NHibernate Features: Proxy Generation

    Did you know that you can leverage NHibernate’s built-in proxy generator to inject custom behavior in your classes? It is called NHibernate.Proxy.DynamicProxy.ProxyFactory and there’s an interface, NHibernate.Proxy.DynamicProxy.IInterceptor, that you can use to extend it, by intercepting method and property calls.

    First, you inject an NHibernate interceptor, inheriting from EmptyInterceptor, in the configuration instance, before building the session factory:

       1: public sealed class NotifyPropertyChangedInterceptor : EmptyInterceptor
       2: {
       3:     private static readonly ProxyFactory factory = new ProxyFactory();
       4:  
       5:     private ISession session = null;
       6:  
       7:     public override void SetSession(ISession session)
       8:     {
       9:         this.session = session;
      10:         base.SetSession(session);
      11:     }
      12:  
      13:     public override Object Instantiate(String clazz, EntityMode entityMode, Object id)
      14:     {
      15:         var entityType = this.session.SessionFactory.GetClassMetadata(clazz).GetMappedClass(entityMode);
      16:         var target = this.session.SessionFactory.GetClassMetadata(entityType).Instantiate(id, entityMode);
      17:         var proxy = factory.CreateProxy(entityType, new _NotifyPropertyChangedInterceptor(target), typeof(INotifyPropertyChanged));
      18:  
      19:         this.session.SessionFactory.GetClassMetadata(entityType).SetIdentifier(proxy, id, entityMode);
      20:  
      21:         return (proxy);
      22:     }
      23: }

    The code in the Instantiate method will add the INotifyPropertyChanged interface to the generated proxy instance, a common interface that is used for detecting property changes.

    But the real fun is in the NHibernate.Proxy.DynamicProxy.IInterceptor implementation:

       1: sealed class _NotifyPropertyChangedInterceptor : NHibernate.Proxy.DynamicProxy.IInterceptor
       2: {
       3:     private PropertyChangedEventHandler changed = delegate { };
       4:     private readonly Object target = null;
       5:  
       6:     public _NotifyPropertyChangedInterceptor(Object target)
       7:     {
       8:         this.target = target;
       9:     }
      10:  
      11:     #region IInterceptor Members
      12:  
      13:     public Object Intercept(InvocationInfo info)
      14:     {
      15:         Object result = null;
      16:  
      17:         if (info.TargetMethod.Name == "add_PropertyChanged")
      18:         {
      19:             var propertyChangedEventHandler = info.Arguments[0] as PropertyChangedEventHandler;
      20:             this.changed += propertyChangedEventHandler;
      21:         }
      22:         else if (info.TargetMethod.Name == "remove_PropertyChanged")
      23:         {
      24:             var propertyChangedEventHandler = info.Arguments[0] as PropertyChangedEventHandler;
      25:             this.changed -= propertyChangedEventHandler;
      26:         }
      27:         else
      28:         {
      29:             result = info.TargetMethod.Invoke(this.target, info.Arguments);
      30:         }
      31:  
      32:         if (info.TargetMethod.Name.StartsWith("set_") == true)
      33:         {
      34:             var propertyName = info.TargetMethod.Name.Substring("set_".Length);
      35:             this.changed(info.Target, new PropertyChangedEventArgs(propertyName));
      36:         }
      37:  
      38:         return (result);
      39:     }
      40:  
      41:     #endregion
      42: }

    This will detect calls to properties (starting with set_) and, after they complete, will raise the PropertyChanged event. This will save you lots of lines in your code!

    You just need to register the NHibernate interceptor, and your done:

       1: cfg.SetInterceptor(new NotifyPropertyChangedInterceptor());

    And from now one, all your entities automagically implement INotifyPropertyChanged:

       1: var product = session.Get<Product>(1);
       2: var npc = product as INotifyProductChanged;
       3: npc.PropertyChanged += (s, e) => 
       4: {
       5:     if (e.PropertyName == "Price")
       6:     {
       7:         Console.WriteLine("Someone changed the price of the product!");
       8:     }
       9: };





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  • Lesser-Known NHibernate Features: Serializable Values

    If you want to store anything in a property of an entity, you can declare it as Object or dynamic; as long as you set it to a value of a serializable type, as supported by BinaryFormatter, you’re good! You can even change the value afterwards to a different type, and it will be saved.

    You map it like this, in mapping by code:

       1: ca.Property(x => x.Payload, x =>
       2: {
       3:     x.Column("`payload`");
       4:     x.NotNullable(false);
       5:     x.Type(NHibernateUtil.Serializable);
       6: });

    Where the class should have a property of type Object or dynamic:

       1: //public virtual Object Payload
       2: public virtual dynamic Payload { get; set; }

    NHibernate will return the same object type and all of its contents anytime you retrieve it.

    Try that in other persistence frameworks! Winking smile


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  • Speech Recognition in ASP.NET

    Speech synthesis and recognition were both introduced in .NET 3.0. They both live in System.Speech.dll. In the past, I already talked about speech synthesis in the context of ASP.NET Web Form applications, this time, I’m going to talk about speech recognition.

    .NET has in fact two APIs for that:

    I am going to demonstrate a technique that makes use of HTML5 features, namely, Data URIs and the getUserMedia API and also ASP.NET Client Callbacks, which, if you have been following my blog, should know that I am a big fan of.

    First, because we have two APIs that we can use, let’s start by creating an abstract base provider class:

       1: public abstract class SpeechRecognitionProvider : IDisposable
       2: {
       3:     protected SpeechRecognitionProvider(SpeechRecognition recognition)
       4:     {
       5:         this.Recognition = recognition;
       6:     }
       7:  
       8:     ~SpeechRecognitionProvider()
       9:     {
      10:         this.Dispose(false);
      11:     }
      12:  
      13:     public abstract SpeechRecognitionResult RecognizeFromWav(String filename);
      14:  
      15:     protected SpeechRecognition Recognition
      16:     {
      17:         get;
      18:         private set;
      19:     }
      20:  
      21:     protected virtual void Dispose(Boolean disposing)
      22:     {
      23:     }
      24:  
      25:     void IDisposable.Dispose()
      26:     {
      27:         GC.SuppressFinalize(this);
      28:         this.Dispose(true);
      29:     }
      30: }

    It basically features one method, RecognizeFromWav, which takes a physical path and returns a SpeechRecognitionResult (code coming next). For completeness, it also implements the Dispose Pattern, because some provider may require it.

    In a moment we will be creating implementations for the built-in .NET provider as well as Microsoft Speech Platform.

    The SpeechRecognition property refers to our Web Forms control, inheriting from HtmlGenericControl, which is the one that knows how to instantiate one provider or the other:

       1: [ConstructorNeedsTag(false)]
       2: public class SpeechRecognition : HtmlGenericControl, ICallbackEventHandler
       3: {
       4:     public SpeechRecognition() : base("span")
       5:     {
       6:         this.OnClientSpeechRecognized = String.Empty;
       7:         this.Mode = SpeechRecognitionMode.Desktop;
       8:         this.Culture = String.Empty;
       9:         this.SampleRate = 44100;
      10:         this.Grammars = new String[0];
      11:         this.Choices = new String[0];
      12:     }
      13:  
      14:     public event EventHandler<SpeechRecognizedEventArgs> SpeechRecognized;
      15:  
      16:     [DefaultValue("")]
      17:     public String Culture
      18:     {
      19:         get;
      20:         set;
      21:     }
      22:  
      23:     [DefaultValue(SpeechRecognitionMode.Desktop)]
      24:     public SpeechRecognitionMode Mode
      25:     {
      26:         get;
      27:         set;
      28:     }
      29:  
      30:     [DefaultValue("")]
      31:     public String OnClientSpeechRecognized
      32:     {
      33:         get;
      34:         set;
      35:     }
      36:  
      37:     [DefaultValue(44100)]
      38:     public UInt32 SampleRate
      39:     {
      40:         get;
      41:         set;
      42:     }
      43:  
      44:     [TypeConverter(typeof(StringArrayConverter))]
      45:     [DefaultValue("")]
      46:     public String [] Grammars
      47:     {
      48:         get;
      49:         private set;
      50:     }
      51:  
      52:     [TypeConverter(typeof(StringArrayConverter))]
      53:     [DefaultValue("")]
      54:     public String[] Choices
      55:     {
      56:         get;
      57:         set;
      58:     }
      59:  
      60:     protected override void OnInit(EventArgs e)
      61:     {
      62:         if (this.Page.Items.Contains(typeof(SpeechRecognition)))
      63:         {
      64:             throw (new InvalidOperationException("There can be only one SpeechRecognition control on a page."));
      65:         }
      66:  
      67:         var sm = ScriptManager.GetCurrent(this.Page);
      68:         var reference = this.Page.ClientScript.GetCallbackEventReference(this, "sound", String.Format("function(result){{ {0}(JSON.parse(result)); }}", String.IsNullOrWhiteSpace(this.OnClientSpeechRecognized) ? "void" : this.OnClientSpeechRecognized), String.Empty, true);
      69:         var script = String.Format("\nvar processor = document.getElementById('{0}'); processor.stopRecording = function(sampleRate) {{ window.stopRecording(processor, sampleRate ? sampleRate : 44100); }}; processor.startRecording = function() {{ window.startRecording(); }}; processor.process = function(sound){{ {1} }};\n", this.ClientID, reference);
      70:  
      71:         if (sm != null)
      72:         {
      73:             this.Page.ClientScript.RegisterStartupScript(this.GetType(), String.Concat("process", this.ClientID), String.Format("Sys.WebForms.PageRequestManager.getInstance().add_pageLoaded(function() {{ {0} }});\n", script), true);
      74:         }
      75:         else
      76:         {
      77:             this.Page.ClientScript.RegisterStartupScript(this.GetType(), String.Concat("process", this.ClientID), script, true);
      78:         }
      79:  
      80:         this.Page.ClientScript.RegisterClientScriptResource(this.GetType(), String.Concat(this.GetType().Namespace, ".Script.js"));
      81:         this.Page.Items[typeof(SpeechRecognition)] = this;
      82:  
      83:         base.OnInit(e);
      84:     }
      85:  
      86:     protected virtual void OnSpeechRecognized(SpeechRecognizedEventArgs e)
      87:     {
      88:         var handler = this.SpeechRecognized;
      89:  
      90:         if (handler != null)
      91:         {
      92:             handler(this, e);
      93:         }
      94:     }
      95:  
      96:     protected SpeechRecognitionProvider GetProvider()
      97:     {
      98:         switch (this.Mode)
      99:         {
     100:             case SpeechRecognitionMode.Desktop:
     101:                 return (new DesktopSpeechRecognitionProvider(this));
     102:  
     103:             case SpeechRecognitionMode.Server:
     104:                 return (new ServerSpeechRecognitionProvider(this));
     105:         }
     106:  
     107:         return (null);
     108:     }
     109:  
     110:     #region ICallbackEventHandler Members
     111:  
     112:     String ICallbackEventHandler.GetCallbackResult()
     113:     {
     114:         AsyncOperationManager.SynchronizationContext = new SynchronizationContext();
     115:  
     116:         var filename = Path.GetTempFileName();
     117:         var result = null as SpeechRecognitionResult;
     118:  
     119:         using (var engine = this.GetProvider())
     120:         {
     121:             var data = this.Context.Items["data"].ToString();
     122:  
     123:             using (var file = File.OpenWrite(filename))
     124:             {
     125:                 var bytes = Convert.FromBase64String(data);
     126:                 file.Write(bytes, 0, bytes.Length);
     127:             }
     128:  
     129:             result = engine.RecognizeFromWav(filename) ?? new SpeechRecognitionResult(String.Empty);
     130:         }
     131:  
     132:         File.Delete(filename);
     133:  
     134:         var args = new SpeechRecognizedEventArgs(result);
     135:  
     136:         this.OnSpeechRecognized(args);
     137:  
     138:         var json = new JavaScriptSerializer().Serialize(result);
     139:  
     140:         return (json);
     141:     }
     142:  
     143:     void ICallbackEventHandler.RaiseCallbackEvent(String eventArgument)
     144:     {
     145:         this.Context.Items["data"] = eventArgument;
     146:     }
     147:  
     148:     #endregion
     149: }

    SpeechRecognition implements ICallbackEventHandler for a self-contained AJAX experience; it registers a couple of JavaScript functions and also an embedded JavaScript file, for some useful sound manipulation and conversion. Only one instance is allowed on a page. On the client-side, this JavaScript uses getUserMedia to access an audio source and uses a clever mechanism to pack them as a .WAV file in a Data URI. I got these functions from http://typedarray.org/from-microphone-to-wav-with-getusermedia-and-web-audio/ and made some changes to them. I like them because they don’t require any external library, which makes all this pretty much self-contained.

    The control exposes some custom properties:

    • Culture: an optional culture name, such as “pt-PT” or “en-US”; if not specified, it defaults to the current culture in the server machine;
    • Mode: one of the two providers: Desktop (for System.Speech) or Server (for Microsoft.Speech, of Microsoft Speech Platform);
    • OnClientSpeechRecognized: the name of a callback JavaScript version that will be called when there are results (more on this later);
    • SampleRate: a sample rate, by default, it is 44100;
    • Grammars: an optional collection of additional grammar files, with extension .grxml (Speech Recognition Grammar Specification), to add to the engine;
    • Choices: an optional collection of choices to recognize, if we want to restrict the scope, such as “yes”/”no”, “red”/”green”, etc.

    The mode enumeration looks like this:

       1: public enum SpeechRecognitionMode
       2: {
       3:     Desktop,
       4:     Server
       5: }

    The SpeechRecognition control also has an event, SpeechRecognized, which allows overriding the detected phrases. Its argument is this simple class that follows the regular .NET event pattern:

       1: [Serializable]
       2: public sealed class SpeechRecognizedEventArgs : EventArgs
       3: {
       4:     public SpeechRecognizedEventArgs(SpeechRecognitionResult result)
       5:     {
       6:         this.Result = result;
       7:     }
       8:  
       9:     public SpeechRecognitionResult Result
      10:     {
      11:         get;
      12:         private set;
      13:     }
      14: }

    Which in turn holds a SpeechRecognitionResult:

       1: public class SpeechRecognitionResult
       2: {
       3:     public SpeechRecognitionResult(String text, params String [] alternates)
       4:     {
       5:         this.Text = text;
       6:         this.Alternates = alternates.ToList();
       7:     }
       8:  
       9:     public String Text
      10:     {
      11:         get;
      12:         set;
      13:     }
      14:  
      15:     public List<String> Alternates
      16:     {
      17:         get;
      18:         private set;
      19:     }
      20: }

    This class receives the phrase that the speech recognition engine understood plus an array of additional alternatives, in descending order.

    The JavaScript file containing the utility functions is embedded in the assembly:

    image

    You need to add an assembly-level attribute, WebResourceAttribute, possibly in AssemblyInfo.cs, of course, replacing MyNamespace for your assembly’s default namespace:

       1: [assembly: WebResource("MyNamespace.Script.js", "text/javascript")]

    This attribute registers a script file with some content-type so that it can be included in a page by the RegisterClientScriptResource method.

    And here is it:

       1: // variables
       2: var leftchannel = [];
       3: var rightchannel = [];
       4: var recorder = null;
       5: var recording = false;
       6: var recordingLength = 0;
       7: var volume = null;
       8: var audioInput = null;
       9: var audioContext = null;
      10: var context = null;
      11:  
      12: // feature detection 
      13: navigator.getUserMedia = navigator.getUserMedia || navigator.webkitGetUserMedia || navigator.mozGetUserMedia || navigator.msGetUserMedia;
      14:  
      15: if (navigator.getUserMedia)
      16: {
      17:     navigator.getUserMedia({ audio: true }, onSuccess, onFailure);
      18: }
      19: else
      20: {
      21:     alert('getUserMedia not supported in this browser.');
      22: }
      23:  
      24: function startRecording()
      25: {
      26:     recording = true;
      27:     // reset the buffers for the new recording
      28:     leftchannel.length = rightchannel.length = 0;
      29:     recordingLength = 0;
      30:     leftchannel = [];
      31:     rightchannel = [];
      32: }
      33:  
      34: function stopRecording(elm, sampleRate)
      35: {
      36:     recording = false;
      37:  
      38:     // we flat the left and right channels down
      39:     var leftBuffer = mergeBuffers(leftchannel, recordingLength);
      40:     var rightBuffer = mergeBuffers(rightchannel, recordingLength);
      41:     // we interleave both channels together
      42:     var interleaved = interleave(leftBuffer, rightBuffer);
      43:  
      44:     // we create our wav file
      45:     var buffer = new ArrayBuffer(44 + interleaved.length * 2);
      46:     var view = new DataView(buffer);
      47:  
      48:     // RIFF chunk descriptor
      49:     writeUTFBytes(view, 0, 'RIFF');
      50:     view.setUint32(4, 44 + interleaved.length * 2, true);
      51:     writeUTFBytes(view, 8, 'WAVE');
      52:     // FMT sub-chunk
      53:     writeUTFBytes(view, 12, 'fmt ');
      54:     view.setUint32(16, 16, true);
      55:     view.setUint16(20, 1, true);
      56:     // stereo (2 channels)
      57:     view.setUint16(22, 2, true);
      58:     view.setUint32(24, sampleRate, true);
      59:     view.setUint32(28, sampleRate * 4, true);
      60:     view.setUint16(32, 4, true);
      61:     view.setUint16(34, 16, true);
      62:     // data sub-chunk
      63:     writeUTFBytes(view, 36, 'data');
      64:     view.setUint32(40, interleaved.length * 2, true);
      65:  
      66:     // write the PCM samples
      67:     var index = 44;
      68:     var volume = 1;
      69:  
      70:     for (var i = 0; i < interleaved.length; i++)
      71:     {
      72:         view.setInt16(index, interleaved[i] * (0x7FFF * volume), true);
      73:         index += 2;
      74:     }
      75:  
      76:     // our final binary blob
      77:     var blob = new Blob([view], { type: 'audio/wav' });
      78:  
      79:     var reader = new FileReader();
      80:     reader.onloadend = function ()
      81:     {
      82:         var url = reader.result.replace('data:audio/wav;base64,', '');
      83:         elm.process(url);
      84:     };
      85:     reader.readAsDataURL(blob);
      86: }
      87:  
      88: function interleave(leftChannel, rightChannel)
      89: {
      90:     var length = leftChannel.length + rightChannel.length;
      91:     var result = new Float32Array(length);
      92:     var inputIndex = 0;
      93:  
      94:     for (var index = 0; index < length;)
      95:     {
      96:         result[index++] = leftChannel[inputIndex];
      97:         result[index++] = rightChannel[inputIndex];
      98:         inputIndex++;
      99:     }
     100:  
     101:     return result;
     102: }
     103:  
     104: function mergeBuffers(channelBuffer, recordingLength)
     105: {
     106:     var result = new Float32Array(recordingLength);
     107:     var offset = 0;
     108:  
     109:     for (var i = 0; i < channelBuffer.length; i++)
     110:     {
     111:         var buffer = channelBuffer[i];
     112:         result.set(buffer, offset);
     113:         offset += buffer.length;
     114:     }
     115:  
     116:     return result;
     117: }
     118:  
     119: function writeUTFBytes(view, offset, string)
     120: {
     121:     for (var i = 0; i < string.length; i++)
     122:     {
     123:         view.setUint8(offset + i, string.charCodeAt(i));
     124:     }
     125: }
     126:  
     127: function onFailure(e)
     128: {
     129:     alert('Error capturing audio.');
     130: }
     131:  
     132: function onSuccess(e)
     133: {
     134:     // creates the audio context
     135:     audioContext = (window.AudioContext || window.webkitAudioContext);
     136:     context = new audioContext();
     137:  
     138:     // creates a gain node
     139:     volume = context.createGain();
     140:  
     141:     // creates an audio node from the microphone incoming stream
     142:     audioInput = context.createMediaStreamSource(e);
     143:  
     144:     // connect the stream to the gain node
     145:     audioInput.connect(volume);
     146:  
     147:     /* From the spec: This value controls how frequently the audioprocess event is 
     148:     dispatched and how many sample-frames need to be processed each call. 
     149:     Lower values for buffer size will result in a lower (better) latency. 
     150:     Higher values will be necessary to avoid audio breakup and glitches */
     151:     var bufferSize = 2048;
     152:  
     153:     recorder = context.createScriptProcessor(bufferSize, 2, 2);
     154:     recorder.onaudioprocess = function (e)
     155:     {
     156:         if (recording == false)
     157:         {
     158:             return;
     159:         }
     160:  
     161:         var left = e.inputBuffer.getChannelData(0);
     162:         var right = e.inputBuffer.getChannelData(1);
     163:  
     164:         // we clone the samples
     165:         leftchannel.push(new Float32Array(left));
     166:         rightchannel.push(new Float32Array(right));
     167:  
     168:         recordingLength += bufferSize;
     169:     }
     170:  
     171:     // we connect the recorder
     172:     volume.connect(recorder);
     173:     recorder.connect(context.destination);
     174: }

    OK, let’s move on the the provider implementations; first, Desktop:

       1: public class DesktopSpeechRecognitionProvider : SpeechRecognitionProvider
       2: {
       3:     public DesktopSpeechRecognitionProvider(SpeechRecognition recognition) : base(recognition)
       4:     {
       5:     }
       6:  
       7:     public override SpeechRecognitionResult RecognizeFromWav(String filename)
       8:     {
       9:         var engine = null as SpeechRecognitionEngine;
      10:  
      11:         if (String.IsNullOrWhiteSpace(this.Recognition.Culture) == true)
      12:         {
      13:             engine = new SpeechRecognitionEngine();
      14:         }
      15:         else
      16:         {
      17:             engine = new SpeechRecognitionEngine(CultureInfo.CreateSpecificCulture(this.Recognition.Culture));
      18:         }
      19:  
      20:         using (engine)
      21:         {
      22:             if ((this.Recognition.Grammars.Any() == false) && (this.Recognition.Choices.Any() == false))
      23:             {
      24:                 engine.LoadGrammar(new DictationGrammar());
      25:             }
      26:  
      27:             foreach (var grammar in this.Recognition.Grammars)
      28:             {
      29:                 var doc = new SrgsDocument(Path.Combine(HttpRuntime.AppDomainAppPath, grammar));
      30:                 engine.LoadGrammar(new Grammar(doc));
      31:             }
      32:  
      33:             if (this.Recognition.Choices.Any() == true)
      34:             {
      35:                 var choices = new Choices(this.Recognition.Choices.ToArray());
      36:                 engine.LoadGrammar(new Grammar(choices));
      37:             }
      38:  
      39:             engine.SetInputToWaveFile(filename);
      40:  
      41:             var result = engine.Recognize();
      42:  
      43:             return ((result != null) ? new SpeechRecognitionResult(result.Text, result.Alternates.Select(x => x.Text).ToArray()) : null);
      44:         }
      45:     }
      46: }

    What this provider does is simply receive the location of a .WAV file and feed it to SpeechRecognitionEngine, together with some parameters of SpeechRecognition (Culture, AudioRate, Grammars and Choices)

    Finally, the code for the Server (Microsoft Speech Platform Software Development Kit) version:

       1: public class ServerSpeechRecognitionProvider : SpeechRecognitionProvider
       2: {
       3:     public ServerSpeechRecognitionProvider(SpeechRecognition recognition) : base(recognition)
       4:     {
       5:     }
       6:  
       7:     public override SpeechRecognitionResult RecognizeFromWav(String filename)
       8:     {
       9:         var engine = null as SpeechRecognitionEngine;
      10:  
      11:         if (String.IsNullOrWhiteSpace(this.Recognition.Culture) == true)
      12:         {
      13:             engine = new SpeechRecognitionEngine();
      14:         }
      15:         else
      16:         {
      17:             engine = new SpeechRecognitionEngine(CultureInfo.CreateSpecificCulture(this.Recognition.Culture));
      18:         }
      19:  
      20:         using (engine)
      21:         {
      22:             foreach (var grammar in this.Recognition.Grammars)
      23:             {
      24:                 var doc = new SrgsDocument(Path.Combine(HttpRuntime.AppDomainAppPath, grammar));
      25:                 engine.LoadGrammar(new Grammar(doc));
      26:             }
      27:  
      28:             if (this.Recognition.Choices.Any() == true)
      29:             {
      30:                 var choices = new Choices(this.Recognition.Choices.ToArray());
      31:                 engine.LoadGrammar(new Grammar(choices));
      32:             }
      33:  
      34:             engine.SetInputToWaveFile(filename);
      35:  
      36:             var result = engine.Recognize();
      37:  
      38:             return ((result != null) ? new SpeechRecognitionResult(result.Text, result.Alternates.Select(x => x.Text).ToArray()) : null);
      39:         }
      40:     }
      41: }

    As you can see, it is very similar to the Desktop one. Keep in mind, however, that for this provider to work you will have to download the Microsoft Speech Platform SDK, the Microsoft Speech Platform Runtime and at least one language from the Language Pack.

    Here is a sample markup declaration:

       1: <web:SpeechRecognition runat="server" ID="processor" ClientIDMode="Static" Mode="Desktop" Culture="en-US" OnSpeechRecognized="OnSpeechRecognized" OnClientSpeechRecognized="onSpeechRecognized" />

    If you want to add specific choices, add the Choices attribute to the control declaration and separate the values by commas:

       1: Choices="One, Two, Three"

    Or add a grammar file:

       1: Grammars="~/MyGrammar.grxml"

    By the way, grammars are not so difficult to create, you can find a good documentation in MSDN: http://msdn.microsoft.com/en-us/library/ee800145.aspx.

    To finalize, a sample JavaScript for starting recognition and receiving the results:

       1: <script type="text/javascript">
       1:  
       2:     
       3:     function onSpeechRecognized(result)
       4:     {
       5:         window.alert('Recognized: ' + result.Text + '\nAlternatives: ' + String.join(', ', result.Alternatives));
       6:     }
       7:  
       8:     function start()
       9:     {
      10:         document.getElementById('processor').startRecording();
      11:     }
      12:  
      13:     function stop()
      14:     {
      15:         document.getElementById('processor').stopRecording();
      16:     }
      17:  
    </script>

    And that’s it. You start recognition by calling startRecording(), get results in onSpeechRecognized() (or any other function set in the OnClientSpeechRecognized property) and stop recording with stopRecording(). The values passed to onSpeechRecognized() are those that may have been filtered by the server-side SpeechRecognized event handler.

    A final word of advisory: because generated sound files may become very large, do keep the recordings as short as possible.

    Of course, this offers several different possibilities, I am looking forward to hearing them from you! Winking smile

    Read more...

  • Loading ASP.NET MVC Controllers and Views From an Assembly

    Back to MVC land! This time, I wanted to be able to load controllers and views from an assembly other than my application. I know about the extensibility mechanisms that ASP.NET and MVC give provides, such as Virtual Path Providers and Controller Factories, so I thought I could use them.

    First things first: we need a controller factory that can load a controller from another assembly:

       1: class AssemblyControllerFactory : DefaultControllerFactory
       2: {
       3:     private readonly IDictionary<String, Type> controllerTypes;
       4:  
       5:     public AssemblyControllerFactory(Assembly assembly)
       6:     {
       7:         this.controllerTypes = assembly.GetExportedTypes().Where(x => (typeof(IController).IsAssignableFrom(x) == true) && (x.IsInterface == false) && (x.IsAbstract == false)).ToDictionary(x => x.Name, x => x);
       8:     }
       9:  
      10:     public override IController CreateController(RequestContext requestContext, String controllerName)
      11:     {
      12:         var controller = base.CreateController(requestContext, controllerName);
      13:  
      14:         if (controller == null)
      15:         {
      16:             var controllerType = this.controllerTypes.Where(x => x.Key == String.Format("{0}Controller", controllerName)).Select(x => x.Value).SingleOrDefault();
      17:             var controllerActivator = DependencyResolver.Current.GetService(typeof (IControllerActivator)) as IControllerActivator;
      18:  
      19:             if (controllerType != null)
      20:             {
      21:                 if (controllerActivator != null)
      22:                 {
      23:                     controller = controllerActivator.Create(requestContext, controllerType);
      24:                 }
      25:                 else
      26:                 {
      27:                     controller = Activator.CreateInstance(controllerType) as IController;
      28:                 }
      29:             }
      30:         }
      31:  
      32:         return (controller);
      33:     }
      34: }

    I inherited AssemblyControllerFactory from DefaultControllerFactory because this class has most of the logic we need, and I just override its CreateController method.

    Next, we need to be able to load view files from an assembly, and a virtual path provider is just what we need for that:

       1: public class AssemblyVirtualPathProvider : VirtualPathProvider
       2: {
       3:     private readonly Assembly assembly;
       4:     private readonly IEnumerable<VirtualPathProvider> providers;
       5:  
       6:     public AssemblyVirtualPathProvider(Assembly assembly)
       7:     {
       8:         var engines = ViewEngines.Engines.OfType<VirtualPathProviderViewEngine>().ToList();
       9:  
      10:         this.providers = engines.Select(x => x.GetType().GetProperty("VirtualPathProvider", BindingFlags.NonPublic | BindingFlags.Instance).GetValue(x, null) as VirtualPathProvider).Distinct().ToList();
      11:         this.assembly = assembly;
      12:     }
      13:  
      14:     public override CacheDependency GetCacheDependency(String virtualPath, IEnumerable virtualPathDependencies, DateTime utcStart)
      15:     {
      16:         if (this.FindFileByPath(this.CorrectFilePath(virtualPath)) != null)
      17:         {
      18:             return (new AssemblyCacheDependency(assembly));
      19:         }
      20:         else
      21:         {
      22:             return (base.GetCacheDependency(virtualPath, virtualPathDependencies, utcStart));
      23:         }
      24:     }
      25:  
      26:     public override Boolean FileExists(String virtualPath)
      27:     {
      28:         foreach (var provider in this.providers)
      29:         {
      30:             if (provider.FileExists(virtualPath) == true)
      31:             {
      32:                 return (true);
      33:             }
      34:         }
      35:  
      36:         var exists = this.FindFileByPath(this.CorrectFilePath(virtualPath)) != null;
      37:  
      38:         return (exists);
      39:     }
      40:  
      41:     public override VirtualFile GetFile(String virtualPath)
      42:     {
      43:         var resource = null as Stream;
      44:  
      45:         foreach (var provider in this.providers)
      46:         {
      47:             var file = provider.GetFile(virtualPath);
      48:  
      49:             if (file != null)
      50:             {
      51:                 try
      52:                 {
      53:                     resource = file.Open();
      54:                     return (file);
      55:                 }
      56:                 catch
      57:                 {
      58:                 }
      59:             }
      60:         }
      61:  
      62:         var resourceName = this.FindFileByPath(this.CorrectFilePath(virtualPath));
      63:  
      64:         return (new AssemblyVirtualFile(virtualPath, this.assembly, resourceName));
      65:     }
      66:  
      67:     protected String FindFileByPath(String virtualPath)
      68:     {
      69:         var resourceNames = this.assembly.GetManifestResourceNames();
      70:  
      71:         return (resourceNames.SingleOrDefault(r => r.EndsWith(virtualPath, StringComparison.OrdinalIgnoreCase) == true));
      72:     }
      73:  
      74:     protected String CorrectFilePath(String virtualPath)
      75:     {
      76:         return (virtualPath.Replace("~", String.Empty).Replace('/', '.'));
      77:     }
      78: }
      79:  
      80: public class AssemblyVirtualFile : VirtualFile
      81: {
      82:     private readonly Assembly assembly;
      83:     private readonly String resourceName;
      84:  
      85:     public AssemblyVirtualFile(String virtualPath, Assembly assembly, String resourceName) : base(virtualPath)
      86:     {
      87:         this.assembly = assembly;
      88:         this.resourceName = resourceName;
      89:     }
      90:  
      91:     public override Stream Open()
      92:     {
      93:         return (this.assembly.GetManifestResourceStream(this.resourceName));
      94:     }
      95: }
      96:  
      97: public class AssemblyCacheDependency : CacheDependency
      98: {
      99:     private readonly Assembly assembly;
     100:  
     101:     public AssemblyCacheDependency(Assembly assembly)
     102:     {
     103:         this.assembly = assembly;
     104:         this.SetUtcLastModified(File.GetCreationTimeUtc(assembly.Location));
     105:     }
     106: }

    These three classes inherit from VirtualPathProvider, VirtualFile and CacheDependency and just override some of its methods. AssemblyVirtualPathProvider first checks with other virtual path providers if a file exists, and only if it doesn’t does it create the AssemblyVirtualFile. This looks up the virtual file name in the assembly’s resources, using a convention that translates slashes (/) per dots (.) and returns it. As for the AssemblyCacheDependency, we need it because otherwise ASP.NET MVC will think that the file exists in a directory and will try to monitor it, and because the directory and file do not exist, it will throw an exception at runtime.

    We also need a bootstrapping class for setting up everything:

       1: public static class AssemblyRoute
       2: {
       3:     public static void MapRoutes(this RouteCollection routes, Assembly assembly)
       4:     {
       5:         ControllerBuilder.Current.SetControllerFactory(new AssemblyControllerFactory(assembly));
       6:         HostingEnvironment.RegisterVirtualPathProvider(new AssemblyVirtualPathProvider(assembly));
       7:     }
       8: }

    Finally, for this to work, we need three things:

    • The controller must be public, have a parameterless constructor, and its name must end with Controller (the default convention);
    • View files must be compiled as embedded resources in the assembly:

    image

    • And finally, we need to set this up in Global.asax.cs or RouteConfig.cs:
       1: routes.MapRoutes(typeof(MyController).Assembly);

    By the way, the AssemblyVirtualPath provider, AssemblyVirtualFile and AssemblyCacheDependency are pretty generic, so you can use them in other scenarios.

    That’s all, folks! Winking smile

    Read more...

  • ASP.NET NHibernateDataSource

    A long, long time ago, I wrote a NHibernateDataSource control. Back then, it was based in the first LINQ provider for NHibernate, and a long has happened since. Now, I decided to give it another go! Smile

    Historically, in ASP.NET, a data control should inherit from DataSourceControl, like ObjectDataSource, LinqDataSource, EntityDataSource, SqlDataSource, etc, and should expose collections for parameters for each of the supported operations (select, update, delete and insert). Since ASP.NET 4, however, a new base class came along: QueryableDataSource. This class is an implementation of IQueryableDataSource, which allows using QueryExtender, also introduced in version 4, to filter and sort the results of a data source that uses LINQ.

    I wanted my control to be able to use QueryExtender, but I also wanted to be able to give it an HQL query. It should also be capable of inserting, updating and deleting entities.

    So, here’s what I came up with, first, the NHibernateDataSource class:

       1: [ParseChildren(true)]
       2: public class NHibernateDataSource : QueryableDataSource
       3: {
       4:     public NHibernateDataSource()
       5:     {
       6:         this.SelectParameters = new ParameterCollection();
       7:         this.InsertParameters = new ParameterCollection();
       8:         this.UpdateParameters = new ParameterCollection();
       9:         this.DeleteParameters = new ParameterCollection();
      10:     }
      11:  
      12:     [Description("Raised when a session factory is built")]
      13:     public event EventHandler<BuildSessionFactoryEventArgs> BuildSessionFactory;
      14:     [Description("Raised when a configuration instance is created")]
      15:     public event EventHandler<ConfigureEventArgs> Configure;
      16:     [Description("Raised when an entity is created for inserts or updates")]
      17:     public event EventHandler<CreateInstanceEventArgs> CreateInstance;
      18:  
      19:     [Description("Raised after an entity is inserted")]
      20:     public event EventHandler<EntityEventArgs> EntityInserted;
      21:     [Description("Raised after an entity is deleted")]
      22:     public event EventHandler<EntityEventArgs> EntityDeleted;
      23:     [Description("Raised after an entity is updated")]
      24:     public event EventHandler<EntityEventArgs> EntityUpdated;
      25:     [Description("Raised after a query is executed")]
      26:     public event EventHandler<EntitiesSelectedEventArgs> EntitiesSelected;
      27:     [Description("Raised when an operation completes (select, insert, update or delete)")]
      28:     public event EventHandler<OperationCompletedEventArgs> OperationCompleted;
      29:  
      30:     [Description("Raised before a select is made")]
      31:     public event EventHandler<EntitiesSelectingEventArgs> EntitiesSelecting;
      32:     [Description("Raised before an entity is inserted")]
      33:     public event EventHandler<EntityEventArgs> EntityInserting;
      34:     [Description("Raised before an entity is deleted")]
      35:     public event EventHandler<EntityEventArgs> EntityDeleting;
      36:     [Description("Raised before an entity is updated")]
      37:     public event EventHandler<EntityEventArgs> EntityUpdating;
      38:  
      39:     [Description("The entity name to update, delete or insert")]
      40:     [DefaultValue("")]
      41:     public String EntityName
      42:     {
      43:         get;
      44:         set;
      45:     }
      46:  
      47:     [Description("The HQL to use for selecting records, when mode Hql is selected")]
      48:     [DefaultValue("")]
      49:     public String Hql
      50:     {
      51:         get;
      52:         set;
      53:     }
      54:  
      55:     [Description("The maximum number of records to retrieve, if paging is not used")]
      56:     [DefaultValue(0)]
      57:     public Int32 MaximumRecords
      58:     {
      59:         get;
      60:         set;
      61:     }
      62:  
      63:     [Description("The page size to retrieve")]
      64:     [DefaultValue(0)]
      65:     public Int32 PageSize
      66:     {
      67:         get;
      68:         set;
      69:     }
      70:  
      71:     [Description("The page index to retrieve")]
      72:     [DefaultValue(0)]
      73:     public Int32 PageIndex
      74:     {
      75:         get;
      76:         set;
      77:     }
      78:  
      79:     [Description("Use HQL or EntityName for selecting")]
      80:     [DefaultValue(NHibernateDataSourceMode.Linq)]
      81:     public NHibernateDataSourceMode Mode
      82:     {
      83:         get;
      84:         set;
      85:     }
      86:  
      87:     [Description("Whether to merge the entity before updating or deleting or not")]
      88:     [DefaultValue(false)]
      89:     public Boolean RefreshBeforeUpdate
      90:     {
      91:         get;
      92:         set;
      93:     }
      94:  
      95:     [Description("Parameters that will be used for the HQL query")]
      96:     public ParameterCollection SelectParameters
      97:     {
      98:         get;
      99:         private set;
     100:     }
     101:  
     102:     [Description("Parameters that will be used for inserting a new entity")]
     103:     public ParameterCollection InsertParameters
     104:     {
     105:         get;
     106:         private set;
     107:     }
     108:  
     109:     [Description("Parameters that will be used for updating an existing entity")]
     110:     public ParameterCollection UpdateParameters
     111:     {
     112:         get;
     113:         private set;
     114:     }
     115:  
     116:     [Description("Parameters that will be used for deleting an existing entity")]
     117:     public ParameterCollection DeleteParameters
     118:     {
     119:         get;
     120:         private set;
     121:     }
     122:  
     123:     [Browsable(false)]
     124:     public ISessionFactory SessionFactory
     125:     {
     126:         get;
     127:         set;
     128:     }
     129:  
     130:     internal static ISessionFactory InternalSessionFactory
     131:     {
     132:         get;
     133:         set;
     134:     }
     135:  
     136:     internal ISessionFactory EffectiveSessionFactory
     137:     {
     138:         get
     139:         {
     140:             var sessionFactory = this.SessionFactory ?? InternalSessionFactory;
     141:             var sfArgs = new BuildSessionFactoryEventArgs() { SessionFactory = sessionFactory };
     142:  
     143:             this.OnBuildSessionFactory(sfArgs);
     144:  
     145:             if (sfArgs.SessionFactory == null)
     146:             {
     147:                 var cfg = new Configuration().Configure();
     148:  
     149:                 var cfgArgs = new ConfigureEventArgs() { Configuration =  cfg };
     150:  
     151:                 this.OnConfigure(cfgArgs);
     152:  
     153:                 cfg = cfgArgs.Configuration;
     154:  
     155:                 sessionFactory = cfg.BuildSessionFactory();
     156:  
     157:                 if (InternalSessionFactory == null)
     158:                 {
     159:                     InternalSessionFactory = sessionFactory;
     160:                 }
     161:             }
     162:             else
     163:             {
     164:                 sessionFactory = sfArgs.SessionFactory;
     165:             }
     166:  
     167:             return (sessionFactory);
     168:         }
     169:     }
     170:  
     171:     protected virtual void OnBuildSessionFactory(BuildSessionFactoryEventArgs e)
     172:     {
     173:         var handler = this.BuildSessionFactory;
     174:  
     175:         if (handler != null)
     176:         {
     177:             handler(this, e);
     178:         }
     179:     }
     180:  
     181:     protected virtual void OnConfigure(ConfigureEventArgs e)
     182:     {
     183:         var handler = this.Configure;
     184:  
     185:         if (handler != null)
     186:         {
     187:             handler(this, e);
     188:         }
     189:     }
     190:  
     191:     protected virtual void OnCreateInstance(CreateInstanceEventArgs e)
     192:     {
     193:         var handler = this.CreateInstance;
     194:  
     195:         if (handler != null)
     196:         {
     197:             handler(this, e);
     198:         }
     199:     }
     200:  
     201:     protected virtual void OnEntitiesSelecting(EntitiesSelectingEventArgs e)
     202:     {
     203:         var handler = this.EntitiesSelecting;
     204:  
     205:         if (handler != null)
     206:         {
     207:             handler(this, e);
     208:         }
     209:     }
     210:  
     211:     protected virtual void OnEntityInserted(EntityEventArgs e)
     212:     {
     213:         var handler = this.EntityInserted;
     214:  
     215:         if (handler != null)
     216:         {
     217:             handler(this, e);
     218:         }
     219:     }
     220:  
     221:     protected virtual void OnEntityDeleted(EntityEventArgs e)
     222:     {
     223:         var handler = this.EntityDeleted;
     224:  
     225:         if (handler != null)
     226:         {
     227:             handler(this, e);
     228:         }
     229:     }
     230:  
     231:     protected virtual void OnEntityUpdated(EntityEventArgs e)
     232:     {
     233:         var handler = this.EntityUpdated;
     234:  
     235:         if (handler != null)
     236:         {
     237:             handler(this, e);
     238:         }
     239:     }
     240:  
     241:     protected virtual void OnEntityInserting(EntityEventArgs e)
     242:     {
     243:         var handler = this.EntityInserting;
     244:  
     245:         if (handler != null)
     246:         {
     247:             handler(this, e);
     248:         }
     249:     }
     250:  
     251:     protected virtual void OnEntityDeleting(EntityEventArgs e)
     252:     {
     253:         var handler = this.EntityDeleting;
     254:  
     255:         if (handler != null)
     256:         {
     257:             handler(this, e);
     258:         }
     259:     }
     260:  
     261:     protected virtual void OnEntityUpdating(EntityEventArgs e)
     262:     {
     263:         var handler = this.EntityUpdating;
     264:  
     265:         if (handler != null)
     266:         {
     267:             handler(this, e);
     268:         }
     269:     }
     270:  
     271:     public virtual void OnEntitiesSelected(EntitiesSelectedEventArgs e)
     272:     {
     273:         var handler = this.EntitiesSelected;
     274:  
     275:         if (handler != null)
     276:         {
     277:             handler(this, e);
     278:         }
     279:     }
     280:  
     281:     public virtual void OnOperationCompleted(OperationCompletedEventArgs e)
     282:     {
     283:         var handler = this.OperationCompleted;
     284:  
     285:         if (handler != null)
     286:         {
     287:             handler(this, e);
     288:         }
     289:     }
     290:  
     291:     public Int32 Insert()
     292:     {
     293:         if (String.IsNullOrWhiteSpace(this.EntityName) == true)
     294:         {
     295:             throw (new InvalidOperationException("The EntityName property cannot be empty."));
     296:         }
     297:  
     298:         if (this.InsertParameters.Count == 0)
     299:         {
     300:             throw (new InvalidOperationException("Missing InsertParameters."));
     301:         }
     302:  
     303:         using (var session = this.EffectiveSessionFactory.OpenStatelessSession())
     304:         using (session.BeginTransaction())
     305:         {
     306:             var args = new EntityEventArgs(this.CreateInstanceAndSetParameters(this.InsertParameters));
     307:  
     308:             this.OnEntityInserting(args);
     309:  
     310:             if (args.Cancel == true)
     311:             {
     312:                 return (0);
     313:             }
     314:  
     315:             session.Insert(args.Entity);
     316:             session.Transaction.Commit();
     317:  
     318:             this.OnEntityInserted(args);
     319:             this.OnOperationCompleted(new OperationCompletedEventArgs(DataSourceOperation.Insert, args.Entity));
     320:         }
     321:  
     322:         return (1);
     323:     }
     324:  
     325:     public Int32 Update()
     326:     {
     327:         if (String.IsNullOrWhiteSpace(this.EntityName) == true)
     328:         {
     329:             throw (new InvalidOperationException("The EntityName property cannot be empty."));
     330:         }
     331:  
     332:         if (this.UpdateParameters.Count == 0)
     333:         {
     334:             throw (new InvalidOperationException("Missing UpdateParameters."));
     335:         }
     336:  
     337:         using (var session = this.EffectiveSessionFactory.OpenStatelessSession())
     338:         using (session.BeginTransaction())
     339:         {
     340:             var args = new EntityEventArgs(this.CreateInstanceAndSetParameters(this.UpdateParameters));
     341:  
     342:             this.OnEntityUpdating(args);
     343:  
     344:             if (args.Cancel == true)
     345:             {
     346:                 return (0);
     347:             }
     348:  
     349:             if (this.RefreshBeforeUpdate == true)
     350:             {
     351:                 this.Refresh(args.Entity);
     352:             }
     353:  
     354:             session.Update(args.Entity);
     355:             session.Transaction.Commit();
     356:  
     357:             this.OnEntityUpdated(args);
     358:             this.OnOperationCompleted(new OperationCompletedEventArgs(DataSourceOperation.Update, args.Entity));
     359:  
     360:             return (1);
     361:         }
     362:     }
     363:  
     364:     public Int32 Delete()
     365:     {
     366:         if (String.IsNullOrWhiteSpace(this.EntityName) == true)
     367:         {
     368:             throw (new InvalidOperationException("The EntityName property cannot be empty."));
     369:         }
     370:  
     371:         using (var session = this.EffectiveSessionFactory.OpenStatelessSession())
     372:         using (session.BeginTransaction())
     373:         {
     374:             var args = new EntityEventArgs(this.CreateInstanceAndSetParameters(this.DeleteParameters));
     375:  
     376:             this.OnEntityDeleting(args);
     377:  
     378:             if (args.Cancel == true)
     379:             {
     380:                 return (0);
     381:             }
     382:  
     383:             if (this.RefreshBeforeUpdate == true)
     384:             {
     385:                 this.Refresh(args.Entity);
     386:             }
     387:  
     388:             session.Delete(args.Entity);
     389:             session.Transaction.Commit();
     390:  
     391:             this.OnEntityDeleted(args);
     392:             this.OnOperationCompleted(new OperationCompletedEventArgs(DataSourceOperation.Delete, args.Entity));
     393:  
     394:             return (1);
     395:         }
     396:     }
     397:  
     398:     protected void Refresh(Object entity)
     399:     {
     400:         using (var session = this.EffectiveSessionFactory.OpenSession())
     401:         {
     402:             session.DefaultReadOnly = true;
     403:             session.FlushMode = FlushMode.Never;
     404:  
     405:             var metadata = this.GetMetadata(this.EntityName);
     406:             var propertiesToLoad = new List<String>();
     407:  
     408:             for (var i = 0; i < metadata.PropertyNames.Length; ++i)
     409:             {
     410:                 if (metadata.GetPropertyValue(entity, metadata.PropertyNames[i], EntityMode.Poco) == null)
     411:                 {
     412:                     if (metadata.PropertyTypes[i].IsEntityType == false)
     413:                     {
     414:                         propertiesToLoad.Add(metadata.PropertyNames[i]);
     415:                     }
     416:                     else
     417:                     {
     418:                         propertiesToLoad.Add(String.Concat(metadata.PropertyNames[i], ".id"));
     419:                     }
     420:                 }
     421:             }
     422:  
     423:             var hql = new StringBuilder();
     424:             hql.Append("select ");
     425:             hql.Append(String.Join(", ", propertiesToLoad));
     426:             hql.AppendFormat(" from {0} where id = :id", entity.GetType().FullName);
     427:  
     428:             var query = session.CreateQuery(hql.ToString());
     429:             query.SetParameter("id", metadata.GetIdentifier(entity, EntityMode.Poco));
     430:  
     431:             var result = query.UniqueResult();
     432:             var values = (result as Object[]) ?? new Object[] { result };
     433:  
     434:             for (var i = 0; i < propertiesToLoad.Count; ++i)
     435:             {
     436:                 var parts = propertiesToLoad[i].Split('.');
     437:                 var value = values[i];
     438:                 var propertyName = parts.First();
     439:  
     440:                 if (parts.Length > 1)
     441:                 {
     442:                     var propertyIndex = Array.IndexOf(metadata.PropertyNames, propertyName);
     443:                     var propertyType = metadata.PropertyTypes[propertyIndex].ReturnedClass;
     444:  
     445:                     value = session.Load(propertyType, values[i]);
     446:                 }
     447:  
     448:                 metadata.SetPropertyValue(entity, propertyName, value, EntityMode.Poco);
     449:             }
     450:         }
     451:     }
     452:  
     453:     protected internal IDictionary<String, Object> GetParameters(ParameterCollection parameters)
     454:     {
     455:         return (parameters.GetValues(this.Context, this).OfType<DictionaryEntry>().ToDictionary(x => x.Key.ToString(), x => x.Value));
     456:     }
     457:  
     458:     protected void SetParameterValues(Object instance, IClassMetadata metadata, IDictionary<String, Object> parameters)
     459:     {
     460:         foreach (var parameter in parameters)
     461:         {
     462:             if (metadata.PropertyNames.Contains(parameter.Key) == true)
     463:             {
     464:                 metadata.SetPropertyValue(instance, parameter.Key, parameter.Value, EntityMode.Poco);
     465:             }
     466:             else if (metadata.IdentifierPropertyName == parameter.Key)
     467:             {
     468:                 metadata.SetIdentifier(instance, parameter.Value, EntityMode.Poco);
     469:             }
     470:         }
     471:     }
     472:  
     473:     protected Object CreateInstanceAndSetParameters(ParameterCollection parameters)
     474:     {
     475:         var metadata = this.GetMetadata(this.EntityName);
     476:  
     477:         if (metadata == null)
     478:         {
     479:             throw (new InvalidOperationException("Entity could not be found."));
     480:         }
     481:  
     482:         var entityType = metadata.GetMappedClass(EntityMode.Poco);
     483:  
     484:         var ciArgs = new CreateInstanceEventArgs(entityType, null);
     485:  
     486:         this.OnCreateInstance(ciArgs);
     487:  
     488:         if (ciArgs.Instance == null)
     489:         {
     490:             ciArgs.Instance = Activator.CreateInstance(entityType);
     491:         }
     492:  
     493:         this.SetParameterValues(ciArgs.Instance, metadata, this.GetParameters(parameters));
     494:  
     495:         return (ciArgs.Instance);
     496:     }
     497:  
     498:     protected internal IClassMetadata GetMetadata(String entityName)
     499:     {
     500:         var metadata = this.EffectiveSessionFactory.GetAllClassMetadata().Where(x => x.Key.EndsWith(entityName)).Select(x => x.Value).SingleOrDefault();
     501:  
     502:         return (metadata);
     503:     }
     504:  
     505:     protected internal void ProcessEntitiesSelecting(EntitiesSelectingEventArgs e)
     506:     {
     507:         this.OnEntitiesSelecting(e);
     508:     }
     509:  
     510:     protected internal void ProcessEntitiesSelected(EntitiesSelectedEventArgs e)
     511:     {
     512:         this.OnEntitiesSelected(e);
     513:         this.OnOperationCompleted(new OperationCompletedEventArgs(DataSourceOperation.Select, e.Results));
     514:     }
     515:  
     516:     protected override QueryableDataSourceView CreateQueryableView()
     517:     {
     518:         return (new NHibernateDataSourceView(this, "DefaultView", this.Context) as QueryableDataSourceView);
     519:     }
     520: }

    You can see that it exposes some events:

    • Configure: gives developers a chance to build (or return an existing) Configuration instance, that will be used for building the session factory;
    • BuildSessionFactory: allows setting parameters on the default session factory or returning an existing one;
    • CreateInstance: raised before NHibernate creates a default instance, to allow developers to return one;
    • EntityInserting: raised before an entity is inserted, allowing developers to cancel the operations or to set entity parameter;
    • EntityUpdating: raised before an entity is updated, allowing developers to cancel the operations or to set entity parameter;
    • EntityDeleting: raised before an entity is deleting, allowing its cancellation;
    • EntitiesSelecting: raised before a select operation is performed;
    • EntityInserted: raised after an entity was inserted;
    • EntityUpdated: raised after an entity was updated;
    • EntityDeleted: raised after an entity was deleted;
    • EntitiesSelected: raised after a select operation was performed;
    • OperationCompleted: raised after an operation completes (select, insert, update or delete).


    If no handler for CreateInstance is supplied, NHibernateDataSource will try to create an entity using Activator.CreateInstance.

    EntitySelecting is raised regardless of the Mode (Hql or Linq), but it will have different values in its argument: a query string plus parameters in the case of Hql and an IQueryable instance for Linq.

    EntityInserting, EntityUpdating and EntityDeleting allow the modification of properties of the entity in the parameter, but not the replacing of the entity itself.

    OperationCompleted is always called, except in the event of an exception.

    It also exposes a couple of properties:

    • Mode: one of the two operation modes, Hql or Linq. If Hql is used, then the Hql property must be set; otherwise, it’s EntityName that is required;
    • Hql: an NHibernate HQL query string;
    • EntityName: the name of an entity that the control will work with; only required for Mode Linq or for inserts, updates or deletes;
    • RefreshBeforeUpdate: whether NHibernate should refresh the properties of an entity before updating or deleting it;
    • MaximumRecords: the optional maximum number of records to retrieve, if paging is not used (PageSize and PageIndex);
    • PageIndex: the page index to retrieve;
    • PageSize: the page size to retrieve;
    • SessionFactory: a session factory that will be used instead of a default created one;
    • SelectParameters: a collection of parameters to be applied to the Hql string;
    • InsertParameters: a collection of parameters for the insert operation;
    • UpdateParameters: a collection of parameters for the update operation;
    • DeleteParameters: a collection of parameters for the delete operation.


    And, of course, exposes the basic operations: select is the default, but Insert, Update and Delete methods are available.

    NHibernateDataSource will check if the SessionFactory property is set, otherwise, it will build its own Configuration instance and raise the Configure and BuildSessionFactory events. The generated session factory is then stored in the InternalSessionFactory static property for caching.

    Then, the NHibernateDataSourceView, which is the responsible for the actual querying, inheriting from QueryableDataSourceView:

       1: public class NHibernateDataSourceView : QueryableDataSourceView
       2: {
       3:     private static readonly MethodInfo queryMethod = typeof (LinqExtensionMethods).GetMethod("Query", BindingFlags.Public | BindingFlags.Static, null, new Type[] { typeof(IStatelessSession) }, null );
       4:     private static readonly MethodInfo toListMethod = typeof(Enumerable).GetMethod("ToList", BindingFlags.Public | BindingFlags.Static);
       5:  
       6:     public NHibernateDataSourceView(NHibernateDataSource dataSource, String viewName, HttpContext context) : base(dataSource, viewName, context)
       7:     {
       8:         this.DataSource = dataSource;
       9:     }
      10:  
      11:     protected NHibernateDataSource DataSource
      12:     {
      13:         get;
      14:         private set;
      15:     }
      16:  
      17:     protected override IEnumerable ExecuteSelect(DataSourceSelectArguments arguments)
      18:     {
      19:         using (var session = this.DataSource.EffectiveSessionFactory.OpenStatelessSession())
      20:         {
      21:             var results = null as IList;
      22:  
      23:             switch (this.DataSource.Mode)
      24:             {
      25:                 case NHibernateDataSourceMode.Hql:
      26:                 {
      27:                     if (String.IsNullOrWhiteSpace(this.DataSource.Hql) == true)
      28:                     {
      29:                         throw (new InvalidOperationException("The Hql property cannot be empty."));
      30:                     }
      31:  
      32:                     var hql = this.DataSource.Hql;
      33:                     var parameters = this.DataSource.GetParameters(this.DataSource.SelectParameters);
      34:                     var args = new EntitiesSelectingEventArgs(hql, parameters, this.DataSource.PageSize, this.DataSource.PageIndex, this.DataSource.MaximumRecords);
      35:  
      36:                     this.DataSource.ProcessEntitiesSelecting(args);
      37:  
      38:                     var query = session.CreateQuery(args.Hql);
      39:  
      40:                     foreach (var param in args.SelectParameters)
      41:                     {
      42:                         if (!(param.Value is IEnumerable) || (param.Value is String) || (param.Value is Byte[]))
      43:                         {
      44:                             query.SetParameter(param.Key, param.Value);
      45:                         }
      46:                         else
      47:                         {
      48:                             query.SetParameterList(param.Key, param.Value as IEnumerable);
      49:                         }
      50:                     }
      51:  
      52:                     if (args.PageSize != 0)
      53:                     {
      54:                         query.SetMaxResults(args.PageSize);
      55:                         query.SetFirstResult(Math.Max((args.PageIndex * args.PageSize) - 1, 0));
      56:                         arguments.MaximumRows = args.PageSize;
      57:                     }
      58:  
      59:                     if (args.MaximumRecords != 0)
      60:                     {
      61:                         query.SetMaxResults(args.MaximumRecords);
      62:                         arguments.MaximumRows = args.MaximumRecords;
      63:                     }
      64:  
      65:                     results = query.List();
      66:  
      67:                     arguments.AddSupportedCapabilities(DataSourceCapabilities.Page);
      68:  
      69:                     if (args.PageSize != 0)
      70:                     {
      71:                         arguments.StartRowIndex = Math.Max((args.PageIndex * args.PageSize) - 1, 0);
      72:                     }
      73:  
      74:                     break;
      75:                 }
      76:  
      77:                 case NHibernateDataSourceMode.Linq:
      78:                 {
      79:                     if (String.IsNullOrWhiteSpace(this.DataSource.EntityName) == true)
      80:                     {
      81:                         throw (new InvalidOperationException("The EntityName property cannot be empty."));
      82:                     }
      83:  
      84:                     var query = queryMethod.MakeGenericMethod(this.EntityType).Invoke(null, new Object[] { session }) as IQueryable;
      85:  
      86:                     var qcea = new QueryCreatedEventArgs(query);
      87:  
      88:                     this.OnQueryCreated(qcea);
      89:  
      90:                     var esaea = new EntitiesSelectingEventArgs(qcea.Query);
      91:  
      92:                     this.DataSource.ProcessEntitiesSelecting(esaea);
      93:  
      94:                     results = toListMethod.MakeGenericMethod(this.EntityType).Invoke(null, new Object[] { esaea.Query }) as IList;
      95:  
      96:                     arguments.AddSupportedCapabilities(DataSourceCapabilities.Page | DataSourceCapabilities.Sort);
      97:  
      98:                     break;
      99:                 }
     100:             }
     101:  
     102:             var entitiesSelectedArgs = new EntitiesSelectedEventArgs(results);
     103:  
     104:             this.DataSource.ProcessEntitiesSelected(entitiesSelectedArgs);
     105:  
     106:             return (entitiesSelectedArgs.Results);
     107:         }
     108:     }
     109:  
     110:     protected override Type EntityType
     111:     {
     112:         get
     113:         {
     114:             return (this.DataSource.GetMetadata(this.DataSource.EntityName).GetMappedClass(EntityMode.Poco));
     115:         }
     116:     }
     117:  
     118:     protected override Object GetSource(QueryContext context)
     119:     {
     120:         throw new NotImplementedException();
     121:     }
     122:  
     123:     protected override void HandleValidationErrors(IDictionary<String, Exception> errors, DataSourceOperation operation)
     124:     {
     125:     }
     126: }

    And the NHibernateDataSourceMode:

       1: public enum NHibernateDataSourceMode
       2: {
       3:     Linq,
       4:     Hql
       5: }

    Finally, all of the event arguments:

       1: [Serializable]
       2: public sealed class BuildSessionFactoryEventArgs : EventArgs
       3: {
       4:     public ISessionFactory SessionFactory
       5:     {
       6:         get;
       7:         set;
       8:     }
       9: }
      10:  
      11: [Serializable]
      12: public sealed class ConfigureEventArgs : EventArgs
      13: {
      14:     public Configuration Configuration
      15:     {
      16:         get;
      17:         set;
      18:     }
      19: }
      20:  
      21: [Serializable]
      22: public sealed class CreateInstanceEventArgs : EventArgs
      23: {
      24:     public CreateInstanceEventArgs(Type type, Object instance)
      25:     {
      26:         this.Type = type;
      27:         this.Instance = instance;
      28:     }
      29:  
      30:     public Type Type
      31:     {
      32:         get;
      33:         private set;
      34:     }
      35:  
      36:     public Object Instance
      37:     {
      38:         get;
      39:         set;
      40:     }
      41: }
      42:  
      43: [Serializable]
      44: public sealed class EntitiesSelectedEventArgs : EventArgs
      45: {
      46:     public EntitiesSelectedEventArgs(IList results)
      47:     {
      48:         this.Results = results;
      49:     }
      50:  
      51:     public IList Results
      52:     {
      53:         get;
      54:         set;
      55:     }
      56: }
      57:  
      58: [Serializable]
      59: public sealed class EntitiesSelectingEventArgs : EventArgs
      60: {
      61:     public EntitiesSelectingEventArgs(IQueryable query)
      62:     {
      63:         this.Query = query;
      64:     }
      65:  
      66:     public EntitiesSelectingEventArgs(String hql, IDictionary<String, Object> selectParameters, Int32 pageSize, Int32 pageIndex, Int32 maximumRecords)
      67:     {
      68:         this.Hql = hql;
      69:         this.SelectParameters = selectParameters;
      70:         this.PageSize = pageSize;
      71:         this.PageIndex = pageIndex;
      72:         this.MaximumRecords = maximumRecords;
      73:     }
      74:  
      75:     public IQueryable Query
      76:     {
      77:         get;
      78:         set;
      79:     }
      80:  
      81:     public String Hql
      82:     {
      83:         get;
      84:         set;
      85:     }
      86:  
      87:     public IDictionary<String, Object> SelectParameters
      88:     {
      89:         get;
      90:         private set;
      91:     }
      92:  
      93:     public Int32 PageSize
      94:     {
      95:         get;
      96:         set;
      97:     }
      98:  
      99:     public Int32 PageIndex
     100:     {
     101:         get;
     102:         set;
     103:     }
     104:  
     105:     public Int32 MaximumRecords
     106:     {
     107:         get;
     108:         set;
     109:     }
     110: }
     111:  
     112: [Serializable]
     113: public sealed class EntityEventArgs : CancelEventArgs
     114: {
     115:     public EntityEventArgs(Object entity)
     116:     {
     117:         this.Entity = entity;
     118:     }
     119:  
     120:     public Object Entity
     121:     {
     122:         get; 
     123:         set;
     124:     }
     125: }
     126:  
     127: [Serializable]
     128: public sealed class OperationCompletedEventArgs : EventArgs
     129: {
     130:     public OperationCompletedEventArgs(DataSourceOperation operation, Object entity)
     131:     {
     132:         this.Entity = entity;
     133:         this.Operation = operation;
     134:     }
     135:  
     136:     public OperationCompletedEventArgs(DataSourceOperation operation, IList results)
     137:     {
     138:         this.Results = results;
     139:         this.Operation = operation;
     140:     }
     141:  
     142:     public DataSourceOperation Operation
     143:     {
     144:         get;
     145:         private set;
     146:     }
     147:  
     148:     public Object Entity
     149:     {
     150:         get;
     151:         protected set;
     152:     }
     153:  
     154:     public IList Results
     155:     {
     156:         get;
     157:         private set;
     158:     }
     159: }

    Now, let’s see concrete examples of its usage. First, using Mode Hql:

       1: <nh:NHibernateDataSource runat="server" ID="nhds" RefreshBeforeUpdate="true" EntityName="Product" Mode="Hql" Hql="from Product p where size(p.OrderDetails) > :size">
       2:     <SelectParameters>
       3:         <asp:Parameter Name="size" DefaultValue="1" Type="Int32" />
       4:     </SelectParameters>
       5:     <InsertParameters>
       6:         <asp:Parameter Name="Name" DefaultValue="Some Name" Type="String" />
       7:         <asp:Parameter Name="Price" DefaultValue="100" Type="Decimal" />
       8:     </InsertParameters>
       9:     <UpdateParameters>
      10:         <asp:QueryStringParameter Name="ProductId" QueryStringField="ProductId" Type="Int32" />
      11:         <asp:QueryStringParameter Name="Price" DefaultValue="50" Type="Decimal" />
      12:     </UpdateParameters>
      13:     <DeleteParameters>
      14:         <asp:QueryStringParameter Name="ProductId" QueryStringField="ProductId" Type="Int32" />
      15:     </DeleteParameters>
      16: </nh:NHibernateDataSource>

    You can see that the Hql property has a parameter, price, which is bound to a parameter in SelectParameters with the same name. Each parameter is an instance of the Parameter class, here I am using a parameter with a static value (Parameter) and another that takes a value from the query string (QueryStringParameter), but others exist. To help with NHibernate insert and update operations, I created a new Parameter class, EntityParameter, that knows how to retrieve a en entity or a proxy to an entity:

       1: public sealed class EntityParameter : Parameter
       2: {
       3:     public EntityParameter()
       4:     {
       5:         this.Lazy = true;
       6:     }
       7:  
       8:     public String EntityName
       9:     {
      10:         get;
      11:         set;
      12:     }
      13:  
      14:     public Object Id
      15:     {
      16:         get;
      17:         set;
      18:     }
      19:  
      20:     public Boolean Lazy
      21:     {
      22:         get;
      23:         set;
      24:     }
      25:  
      26:     protected override Parameter Clone()
      27:     {
      28:         return (new EntityParameter(){ EntityName = this.EntityName, Id = this.Id });
      29:     }
      30:  
      31:     protected override Object Evaluate(HttpContext context, Control control)
      32:     {
      33:         var dataSource = control as NHibernateDataSource;
      34:  
      35:         if (dataSource == null)
      36:         {
      37:             throw (new InvalidOperationException("EntityParameter can only be used with NHibernateDataSource."));
      38:         }
      39:  
      40:         using (var session = dataSource.EffectiveSessionFactory.OpenStatelessSession())
      41:         {
      42:             var metadata = dataSource.GetMetadata(this.EntityName);
      43:  
      44:             if (metadata == null)
      45:             {
      46:                 throw (new InvalidOperationException("Entity could not be found."));
      47:             }
      48:  
      49:             var entityType = metadata.GetMappedClass(EntityMode.Poco);
      50:             var idType = metadata.IdentifierType.ReturnedClass;
      51:             var id = Convert.ChangeType(this.Id, idType);
      52:             var entity = (this.Lazy == true) ? (metadata as IEntityPersister).CreateProxy(id, session.GetSessionImplementation()) : session.Get(entityType.FullName, id);
      53:  
      54:             return (entity);
      55:         }
      56:     }
      57: }

    As for Mode Linq, an example using a QueryExtender is in order:

       1: <asp:TextBox runat="server" ID="name"/>
       2:  
       3: <asp:QueryExtender runat="server" TargetControlID="nhds">
       4:     <asp:SearchExpression DataFields="Name" SearchType="StartsWith">
       5:         <asp:ControlParameter ControlID="name" />
       6:     </asp:SearchExpression>
       7:     <asp:OrderByExpression DataField="Price" Direction="Descending" />
       8: </asp:QueryExtender>
       9:  
      10: <nh:NHibernateDataSource runat="server" ID="nhds" RefreshBeforeUpdate="true" EntityName="Product" Mode="Linq">
      11:     <InsertParameters>
      12:         <asp:Parameter Name="Name" DefaultValue="Some Name" Type="String" />
      13:         <asp:Parameter Name="Price" DefaultValue="100" Type="Decimal" />
      14:     </InsertParameters>
      15:     <UpdateParameters>
      16:         <asp:QueryStringParameter QueryStringField="ProductId" Name="ProductId" Type="Int32" />
      17:         <asp:Parameter Name="Price" DefaultValue="50" Type="Decimal" />
      18:     </UpdateParameters>
      19:     <DeleteParameters>
      20:         <asp:QueryStringParameter QueryStringField="ProductId" Name="ProductId" Type="Int32" />
      21:     </DeleteParameters>
      22: </nh:NHibernateDataSource>

    The LINQ query produced by the NHibernateDataSource is intercepted by the QueryExtender and a where (SearchExpression) and a order by (OrderByExpression) clauses are added to it. Other expressions can be used, inheriting from DataSourceExpression, and some take parameters of type Parameter. Do notice that filtering and sorting is performed server-side, not client-side.

    Of course, this can certainly be improved, let me hear your thoughts and questions.

    And that’s it. Enjoy!

    Read more...

  • Entity Framework Pitfalls: Registering Custom Database Functions for LINQ

    Like I said in my previous post, it’s not enough to add a DbFunctionAttribute attribute to a method to have it call a database function. If the function is not a built-in one, it will not be registered in the Entity Framework provider manifest for SQL Server, so it will require registration in the model. You might think, just by looking at the methods in SqlFunctions that all that it took was to add this attribute, but you would be wrong.

    Read more...

  • Registering SQL Server Built-in Functions to Entity Framework Code First

    It is possible to register custom functions that exist in the database so that they can be called by Entity Framework Code First LINQ queries.

    For example, consider the SOUNDEX function (yes, I know, I know, I always give SOUNDEX as an example for LINQ extensions! Winking smile). We could write it in C# as this:

       1: public static String Soundex(this String input)
       2: {
       3:     const String values = "01230120022455012623010202";
       4:     const Int32 encodingLength = 4;
       5:  
       6:     var prevChar = ' ';
       7:  
       8:     input = Normalize(input);
       9:  
      10:     if (input.Length == 0)
      11:     {
      12:         return (input);
      13:     }
      14:  
      15:     var builder = new StringBuilder(input[0]);
      16:  
      17:     for (var i = 1; ((i < input.Length) && (builder.Length < encodingLength)); ++i)
      18:     {
      19:         var c = values[input[i] - 'A'];
      20:  
      21:         if ((c != '0') && (c != prevChar))
      22:         {
      23:             builder.Append(c);
      24:             prevChar = c;
      25:         }
      26:     }
      27:  
      28:     while (builder.Length < encodingLength)
      29:     {
      30:         builder.Append('0');
      31:     }
      32:  
      33:     return (builder.ToString());
      34: }
      35:  
      36: private static String Normalize(String text)
      37: {
      38:     var builder = new StringBuilder();
      39:  
      40:     foreach (var c in text)
      41:     {
      42:         if (Char.IsLetter(c) == true)
      43:         {
      44:             builder.Append(Char.ToUpper(c));
      45:         }
      46:     }
      47:  
      48:     return (builder.ToString());
      49: }

    If we want this method to be callable by a LINQ query, we need to add the DbFunctionAttribute to it, specifying the name of the database function we wish to call, because the .NET method and the database function names can be different:

       1: [DbFunction("SqlServer", "SOUNDEX")]
       2: public static String Soundex(this String input)
       3: {
       4:     //...
       5: }

    And for calling it:

       1: var soundexNames = ctx.Projects.Select(p => p.Name.Soundex()).ToList();

    However, for certain database functions, it requires a bit more work to get done. Let us consider now the FORMAT function and a .NET implementation:

       1: public static String Format(this DateTime value, String format, String culture)
       2: {
       3:     return (value.ToString(format, CultureInfo.CreateSpecificCulture(culture)));
       4: }

    Besides adding the DbFunctionAttribute attribute:

       1: [DbFunction("CodeFirstDatabaseSchema", "FORMAT")]
       2: public static String Format(this DateTime value, String format, String culture)
       3: {
       4:     //...
       5: }

    it also requires that we register it explicitly in our model, for that, we override the OnModelCreating method and add a custom convention:

       1: protected override void OnModelCreating(DbModelBuilder modelBuilder)
       2: {
       3:     modelBuilder.Conventions.Add(new RegisterFunctionConvention());
       4:  
       5:     base.OnModelCreating(modelBuilder);
       6: }

    The convention being:

       1: public class RegisterFunctionConvention : IStoreModelConvention<EdmModel>
       2: {
       3:     public void Apply(EdmModel item, DbModel model)
       4:     {
       5:         var valueParameter = FunctionParameter.Create("value", this.GetStorePrimitiveType(model, PrimitiveTypeKind.DateTime), ParameterMode.In);
       6:         var formatParameter = FunctionParameter.Create("format", this.GetStorePrimitiveType(model, PrimitiveTypeKind.String), ParameterMode.In);
       7:         var cultureParameter = FunctionParameter.Create("culture", this.GetStorePrimitiveType(model, PrimitiveTypeKind.String), ParameterMode.In);
       8:         var returnValue = FunctionParameter.Create("result", this.GetStorePrimitiveType(model, PrimitiveTypeKind.String), ParameterMode.ReturnValue);
       9:  
      10:         var function = this.CreateAndAddFunction(item, "FORMAT", new[] { valueParameter, formatParameter, cultureParameter }, new[] { returnValue });
      11:     }
      12:  
      13:     protected EdmFunction CreateAndAddFunction(EdmModel item, String name, IList<FunctionParameter> parameters, IList<FunctionParameter> returnValues)
      14:     {
      15:         var payload = new EdmFunctionPayload { StoreFunctionName = name, Parameters = parameters, ReturnParameters = returnValues, Schema = this.GetDefaultSchema(item), IsBuiltIn = true };
      16:         var function = EdmFunction.Create(name, this.GetDefaultNamespace(item), item.DataSpace, payload, null);
      17:  
      18:         item.AddItem(function);
      19:  
      20:         return (function);
      21:     }
      22:  
      23:     protected EdmType GetStorePrimitiveType(DbModel model, PrimitiveTypeKind typeKind)
      24:     {
      25:         return (model.ProviderManifest.GetStoreType(TypeUsage.CreateDefaultTypeUsage(PrimitiveType.GetEdmPrimitiveType(typeKind))).EdmType);
      26:     }
      27:  
      28:     protected String GetDefaultNamespace(EdmModel layerModel)
      29:     {
      30:         return (layerModel.GlobalItems.OfType<EdmType>().Select(t => t.NamespaceName).Distinct().Single());
      31:     }
      32:  
      33:     protected String GetDefaultSchema(EdmModel layerModel)
      34:     {
      35:         return (layerModel.Container.EntitySets.Select(s => s.Schema).Distinct().SingleOrDefault());
      36:     }
      37: }

    I got some of the metadata code from Diego Vega’s (@divega) repository: https://github.com/divega/, but changed it slightly.

    Now we have the FORMAT function available to LINQ:

       1: var projectDates = ctx.Projects.Select(p => p.Start.Format("D", "pt-PT")).ToList();

    Now, I hear you ask: why for SOUNDEX we just need to add a simple attribute and for FORMAT we need so much more? Well, it just happens that SOUNDEX is defined in the Entity Framework SQL Server provider manifest - see it here. All of the functions in SqlFunctions are present in the manifest, but the opposite is not true - not all functions in the manifest are in SqlFunctions, but that's the way it is! Thanks to @divega for the explanation.

    Some things worth mentioning:

    • The namespace and name used in the DbFunctionAttribute attribute must match those passed to EdmFunction.Create (CodeFirstDatabaseSchema is what GetDefaultNamespace returns;
    • You cannot specify two functions with the same name and different parameters.

    There is an open request to add the FORMAT function to the list of functions supported out of the box by Entity Framework Code First: https://entityframework.codeplex.com/workitem/2586 through the SqlFunctions class, but in the meantime, this might be useful!

    Read more...