Knowledgebase

When you use a metadata class in Entity Framework the registration between the entity and the metadata class is not registered for all Microsoft Visual Studio Project types (the "test project class library" for example).

I found the solution at: http://stackoverflow.com/questions/2657358/net-4-rtm-metadatatype-attribute-ignored-when-using-validator. It demonstrates registring all metadata classes in an assembly.

Solution

Add the following class, to the assembly that contains the Entity Framework model (*.edmx) and the metadata classes:

using System;
using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
using System.Reflection;

/// <summary>
/// Metadata classes are not always automatically registered, for example in a UnitTest classlibrary.
/// This class can be used to register all metadata classes find in this assembly.
/// 
/// Registration will only be done once.
/// </summary>
public static class MetadataTypesRegister
{
    private static bool _installed = false;
    private static readonly object InstalledLock = new object();


    /// <summary>
    /// Register all metadata classes found in this assembly.
    /// Registration will only be done once.        
    /// </summary>
    public static void InstallForAssembly()
    {
        if (_installed)
        {
            return;
        }

        lock (InstalledLock)
        {
            if (_installed)
            {
                return;
            }

            foreach (Type type in Assembly.GetExecutingAssembly().GetTypes())
            {
                foreach (MetadataTypeAttribute attrib in type.GetCustomAttributes(typeof(MetadataTypeAttribute), true))
                {
                    TypeDescriptor.AddProviderTransparent(new AssociatedMetadataTypeTypeDescriptionProvider(type, attrib.MetadataClassType), type);
                }
            }

            _installed = true;
        }
    }
}

In entity framework, you define metadata attributes in an internal sealed metadata "buddy" class like:

[MetadataType(typeof(CustomerMetadata))]
    public partial class Customer
    {
        internal sealed class CustomerMetadata
        {

            [Required(ErrorMessage = "Id is required")]
            public Int32 Id { get; set; }

            [Required(ErrorMessage = "Name is required")]
            public String Name { get; set; }

            [DataType(DataType.EmailAddress)]
            public String Email { get; set; }

            [RegularExpression("^[0-9]{4}[a-z|A-Z]{2}$")]
            public String Zipcode { get; set; }

        }
    }

You can unit test the metadata attributes by using the following unit test class.

using System;
using System.Text;
using System.Collections.Generic;
using System.Linq;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using Research.Dal2;
using System.ComponentModel.DataAnnotations;

[TestClass]
public class CustomerTester
{
    private TestContext testContextInstance;

    /// <summary>
    ///Gets or sets the test context which provides
    ///information about and functionality for the current test run.
    ///</summary>
    public TestContext TestContext
    {
        get
        {
            return testContextInstance;
        }
        set
        {
            testContextInstance = value;
        }
    }

    [ClassInitialize()]
    public static void MyClassInitialize(TestContext testContext) 
    {
        MetadataTypesRegister.InstallForAssembly();
    }
    
    [TestMethod]
    public void ValidateZipcodeTest()
    {
        var customer = new Research.Dal2.Customer();
        customer.Zipcode = "this is a wrong zipcode";
        var vc = new ValidationContext(customer, null, null) { MemberName = "Zipcode" };
        var validationResults = new List<ValidationResult>();

        // Validate only the zip code.
        bool isValidZipCode = Validator.TryValidateProperty(customer.Zipcode, vc, validationResults);
        Assert.IsFalse(isValidZipCode);

        // Validate the whole Customer entity.
        bool isValidCustomer = Validator.TryValidateObject(customer, vc, validationResults, true);
        Assert.IsFalse(isValidCustomer);
    }
}