Cannot obtain Metadata from WCF service when using Microsoft WCF Test Client.

I just finished writing the technical whitepapers for my product activation service, so I started the actual implementation using WCF services. All was good, added the usual WCF Service Application project, ran a quick F5, and swapped out all the default services with my own. Then I ran a F5 debug, and wait what? The WCF Test Client could not run my service.

Microsoft WCF Test Client

Failed to add a service. Service metadata may not be accessible. Make sure your service is running and exposing metadata.

I vigorously checked the configuration, because I often write my by hand instead of using the WCF tool, and everything checked out. Here is what my configuration looked like, which is a valid configuration.

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <system.web>
        <compilation debug="true" />
    </system.web>
    <system.serviceModel>
        <services>
            <service name="DCOMProductions.Activation.ActivationService">
                <endpoint binding="wsHttpBinding" contract="DCOMProductions.Activation.IActivationService">
                    <identity>
                        <dns value="localhost" />
                    </identity>
                </endpoint>
                <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange" />
                <host>
                    <baseAddresses>
                        <add baseAddress="http://localhost:8732/Design_Time_Addresses/DCOMProductions.Activation/ActivationService/" />
                    </baseAddresses>
                </host>
            </service>
        </services>
        <behaviors>
            <serviceBehaviors>
                <behavior>
                    <serviceMetadata httpGetEnabled="true" />
                    <serviceDebug includeExceptionDetailInFaults="true" />
                </behavior>
            </serviceBehaviors>
        </behaviors>
    </system.serviceModel>
</configuration>

What the heck? Because everything I could think of is valid, I then pointed my finger at something being wrong with my code. Something has to be causing the test client to fail. I tested this theory by navigating to the service address in Internet Explorer, which revealed that it was encountering a server error, which proved my theory.

Taking a look at my code, I quickly realized that I had some Composite Types in my service. One of the composite types is an Enum.

//-----------------------------------------------------------------------------
// <copyright file="ActivationResult.cs" company="DCOM Productions">
//     Copyright (c) DCOM Productions.  All rights reserved.
// </copyright>
//-----------------------------------------------------------------------------

namespace DCOMProductions.Activation
{
    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Text;
    using System.Runtime.Serialization;

    /// <summary>
    /// The result of the activation request
    /// </summary>
    [DataContract]
    public enum ActivationResult
    {
        [DataMember]
        None,
        [DataMember]
        Passed
    }
}

If you notice, I have highlighted lines 21 and 23. The problem is that enumeration fields should use the EnumMemberAttribute, and not DataMemberAttribute. I changed the attributes, ran a F5 debug and low-and-behold, the service worked great.

If you find yourself pulling your hair out over WCF configuration problems, check your code too. It may just be something simple.