Delegate of web service interface erroring

Question

I am trying to call methods on a web service using delegate calls:

public IEnumerable<MyDataType> List(bool showDeleted)
{
    var result = ResponseHelper<dynamic[], IEnumerable<MyDataType>>(new dynamic[] {InstanceGuid, showDeleted}, "List");
    return result;
}

public MyDataType Get(int myDataTypeId, bool showDeleted)
{
    var result = ResponseHelper<dynamic[], MyDataType>(new dynamic[] {InstanceGuid, myDataTypeId, showDeleted}, "Get");
    return result;
}


public static R ResponseHelper<T, R>(T parameters, string serviceAction)
{
    var results = default(R);
    foreach (var service in _webServiceCoordinator.GetServices())
    {
        var func = (Func<T, R>)Delegate.CreateDelegate(typeof(Func<T, R>), service, serviceAction);
        try
        {
            results = func(parameters);
            break;
        }
        catch
        {
            _webServiceCoordinator.LastServiceFaulted();
        }
    }
    return results;
}

The method _webServiceCoordinator.GetServices() returns an IEnumerable of System.Runtime.Remoting.Proxies.__TransparentProxy containing services of this contract:

public interface IOverrideService : IWebService
{
    IEnumerable<MyDataType> List(Guid instanceGuid, bool showDeleted);
    MyDataTypeGet(Guid instanceGuid, int myDataTypeId, bool showDeleted);
}

The error I receive at the Delegate.CreateDelegate line is:

Cannot bind to the target method because its signature or security transparency is not compatible with that of the delegate type.

My thoughts are it's failing because it's a delegate of a proxy class, but (in my mind) a pointer of a pointer should still work.

I wondered if it was related to this question, even though I get a different error message.

It is a .Net 4.0 project, but I am using VS2012 (so have .NET 4.5 installed)