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Localizing Default Error Messages in ASP.NET MVC and WebForm

        Introduction:


                    System.ComponentModel.DataAnnotations validation attributes (like RequiredAttribute) allows us to localize error messages using ErrorMessageResourceName and ErrorMessageResourceType. But some error messages cannot be localized using these properties. For example, 'The value X is not valid for Y'.  In this article, I will quickly show you how to localize these error messages in ASP.NET MVC and ASP.NET WebForm.


        Description:


                    For localizing default error messages in ASP.NET MVC we will set these below properties in Global.asax Application_Start method,


view sourceprint?
1 ClientDataTypeModelValidatorProvider.ResourceClassKey = "MyResources";
2 DefaultModelBinder.ResourceClassKey = "MyResources";

                    Next, create a MyResources.resx resource file and/or your culture specific resource file MyResources.xx.resx inside App_GlobalResources folder where we can override FieldMustBeDate, FieldMustBeNumeric, PropertyValueInvalid and PropertyValueRequired messages. Here are the default values,


view sourceprint?
1 FieldMustBeDate The field {0} must be a date.
2 FieldMustBeNumeric The field {0} must be a number.
3 PropertyValueInvalid The value '{0}' is not valid for {1}.
4 PropertyValueRequired A value is required.


                    For WebForm, we need to localize PropertyValueInvalid and PropertyValueRequired. But here we need to do some more work. Just add a class MyErrorMessageProvider.cs which do all the work for us(Note: most code are copied from System.Web.dll), 


view sourceprint?
01     public class MyErrorMessageProvider
02 {
03     private static string _resourceClassKey;
04  
05     public static void SetResourceClassKey(string resourceClassKey){
06         if(resourceClassKey == null){
07             throw new ArgumentNullException("resourceClassKey");
08         }
09         _resourceClassKey = resourceClassKey;
10         ModelBinderErrorMessageProviders.ValueRequiredErrorMessageProvider = MyErrorMessageProvider.DefaultValueRequiredErrorMessageProvider;
11         ModelBinderErrorMessageProviders.TypeConversionErrorMessageProvider = MyErrorMessageProvider.DefaultTypeConversionErrorMessageProvider;
12     }
13  
14     private static string DefaultTypeConversionErrorMessageProvider(ModelBindingExecutionContext modelBindingExecutionContext, ModelMetadata modelMetadata, object incomingValue)
15     {
16         return GetResourceCommon(modelBindingExecutionContext, modelMetadata, incomingValue, new Func<ModelBindingExecutionContext, string>(GetValueInvalidResource));
17     }
18  
19     private static string DefaultValueRequiredErrorMessageProvider(ModelBindingExecutionContext modelBindingExecutionContext, ModelMetadata modelMetadata, object incomingValue)
20     {
21         return GetResourceCommon(modelBindingExecutionContext, modelMetadata, incomingValue, new Func<ModelBindingExecutionContext, string>(GetValueRequiredResource));
22     }
23  
24     private static string GetResourceCommon(ModelBindingExecutionContext modelBindingExecutionContext, ModelMetadata modelMetadata, object incomingValue, Func<ModelBindingExecutionContext, string> resourceAccessor)
25     {
26         string displayName = modelMetadata.GetDisplayName();
27         string str = resourceAccessor(modelBindingExecutionContext);
28         object[] objArray = new object[2];
29         objArray[0] = incomingValue;
30         objArray[1] = displayName;
31         string str1 = string.Format(CultureInfo.CurrentCulture, str, objArray);
32         return str1;
33     }
34  
35     private static string GetUserResourceString(ModelBindingExecutionContext modelBindingExecutionContext, string resourceName, string resourceClassKey)
36     {
37         if (string.IsNullOrEmpty(resourceClassKey) || modelBindingExecutionContext == null || modelBindingExecutionContext.HttpContext == null)
38         {
39             return null;
40         }
41         else
42         {
43             return modelBindingExecutionContext.HttpContext.GetGlobalResourceObject(resourceClassKey, resourceName, CultureInfo.CurrentUICulture) as string;
44         }
45     }
46  
47     private static string GetUserResourceString(ModelBindingExecutionContext modelBindingExecutionContext, string resourceName)
48     {
49         return GetUserResourceString(modelBindingExecutionContext, resourceName, _resourceClassKey);
50     }
51  
52     private static string GetValueInvalidResource(ModelBindingExecutionContext modelBindingExecutionContext)
53     {
54         string userResourceString = GetUserResourceString(modelBindingExecutionContext, "PropertyValueInvalid");
55         return userResourceString;
56     }
57  
58     private static string GetValueRequiredResource(ModelBindingExecutionContext modelBindingExecutionContext)
59     {
60         string userResourceString = GetUserResourceString(modelBindingExecutionContext, "PropertyValueRequired");
61         return userResourceString;
62     }
63 }

 

                     and then we can set our resource class file at Global.asax Application_Start method,

 



view sourceprint?
1 MyErrorMessageProvider.SetResourceClassKey("MyResources");


 

        Summary:


                    In this article, I showed you how easily we can localize error messages in ASP.NET MVC and ASP.NET WebForm . Hopefully you will enjoy my this article too.



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