Default resource for data annotations in ASP.NET MVC

Question

There\'s a way to set the default resource to the data annotations validations?

I don\'t wanna make something like this:

[Required(ErrorMessage=\"Nam         


        

Answer 1

To achieve this, I created a new class that inherits from RequiredAttribute, and the error message is embedded inside this new class:

public class RequiredWithMessageAttribute : RequiredAttribute
{
    public RequiredWithMessageAttribute()
    {
        ErrorMessageResourceType = typeof(ValidationResource);
        ErrorMessageResourceName = "RequiredErrorMessage";
    }
}

The error message is taken from the ValidationResource.resx file, where I list the error message as follows:

RequiredErrorMessage --> "{0} is required."

where {0} = display name.

I then annotate my models like this, so I never have to repeat my error message declarations:

[RequiredWithMessage]
public string Name { get; set; }

Once you do this, an error message ("Name is required.") will appear whenever validation fails.

This works properly with ASP.NET MVC's server-side validation and client-side validation.

Answer 2

You could try doing this:

Add this class somewhere in your project:

 public class ExternalResourceDataAnnotationsValidator : DataAnnotationsModelValidator<ValidationAttribute>
{
    /// <summary>
    /// The type of the resource which holds the error messqages
    /// </summary>
    public static Type ResourceType { get; set; }

    /// <summary>
    /// Function to get the ErrorMessageResourceName from the Attribute
    /// </summary>
    public static Func<ValidationAttribute, string> ResourceNameFunc 
    {
        get { return _resourceNameFunc; }
        set { _resourceNameFunc = value; }
    }
    private static Func<ValidationAttribute, string> _resourceNameFunc = attr => attr.GetType().Name;

    public ExternalResourceDataAnnotationsValidator(ModelMetadata metadata, ControllerContext context, ValidationAttribute attribute)
        : base(metadata, context, attribute)
    {
        if (Attribute.ErrorMessageResourceType == null)
        {
            this.Attribute.ErrorMessageResourceType = ResourceType;
        }

        if (Attribute.ErrorMessageResourceName == null)
        {
            this.Attribute.ErrorMessageResourceName = ResourceNameFunc(this.Attribute);
        }
    }
}

and in your global.asax, add the following:

// Add once
ExternalResourceDataAnnotationsValidator.ResourceType = typeof(CustomDataAnnotationsResources);

// Add one line for every attribute you want their ErrorMessageResourceType replaced.
DataAnnotationsModelValidatorProvider.RegisterAdapter(typeof(RangeAttribute), typeof(ExternalResourceDataAnnotationsValidator));

It will look for a property with the same name as the validator type for the error message. You can change that via the ResourceNameFunc property.

EDIT: AFAIK this works from MVC2 onwards, as DataAnnotationsModelValidatorProvider was introduced in MVC2.

Answer 3

I did another approach. It still needs you to inherit DataAnnotation attributes, but you can get a more flexible translation solution.

Code from my blog post (read it fore more details)

End result

public class User
{
    [Required]
    [LocalizedDisplayNameAttribute("User_Id")]
    public int Id { get; set; }

    [Required]
    [StringLength(40)]
    [LocalizedDisplayNameAttribute("User_FirstName")]
    public string FirstName { get; set; }

    [Required]
    [StringLength(40)]
    [LocalizedDisplayNameAttribute("User_LastName")]
    public string LastName { get; set; }
}

1 Inherit all data annotation attributes like this

public class RequiredAttribute : System.ComponentModel.DataAnnotations.RequiredAttribute
{
    private string _displayName;

    public RequiredAttribute()
    {
        ErrorMessageResourceName = "Validation_Required";
    }

    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        _displayName = validationContext.DisplayName;
        return base.IsValid(value, validationContext);
    }

    public override string FormatErrorMessage(string name)
    {
        var msg = LanguageService.Instance.Translate(ErrorMessageResourceName);
        return string.Format(msg, _displayName);
    }
}

2 Inherit DisplayNameAttribute

public class LocalizedDisplayNameAttribute : DisplayNameAttribute
{
    private PropertyInfo _nameProperty;
    private Type _resourceType;

    public LocalizedDisplayNameAttribute(string className, string propertyName)
        : base(className + (propertyName == null ? "_Class" : ("_" + propertyName)))
    {

    }

    public override string DisplayName
    {
        get
        {
            return LanguageService.Instance.Translate(base.DisplayName) ?? "**" + base.DisplayName + "**";
        }
    }
}

3. Create the language service (you can switch to any language source in it)

public class LanguageService
{
    private static LanguageService _instance = new LanguageService();
    private List<ResourceManager> _resourceManagers = new List<ResourceManager>();

    private LanguageService()
    {
    }

    public static LanguageService Instance { get { return _instance; } }

    public void Add(ResourceManager mgr)
    {
        _resourceManagers.Add(mgr);
    }

    public string Translate(string key)
    {
        foreach (var item in _resourceManagers)
        {
            var value = item.GetString(key);
            if (value != null)
                return value;
        }

        return null;
    }
}

Finally you need to register the string tables you use to translate the validation messages and your models

LanguageService.Instance.Add(MyNameSpace.ModelResource.ResourceManager);
LanguageService.Instance.Add(MyNameSpace.ValidationResources.ResourceManager);