Localizing Default Error Messages in ASP.NET MVC and WebForm

Sunday, March 31, 2013

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,

`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,

1FieldMustBeDate The field {0} must be a date.
2FieldMustBeNumeric The field {0} must be a number.
3PropertyValueInvalid The value '{0}' is not valid for {1}.
4PropertyValueRequired 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),

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,

`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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