superType#IsAssignableFrom(subType) won't return true when the type on the left side is a generic and the type parameter on the right is its subtype. This extension method does it. I ripped it off of this answer from SO: http://stackoverflow.com/a/1075059/34315.

IsGenericTypeAssignableFromExtension.cs

public static class TypeExtensions
{
    public static bool IsGenericTypeAssignableFrom(this Type genericType, Type givenType)
    {
        var interfaceTypes = givenType.GetInterfaces();

        if (interfaceTypes.Any(it => it.IsGenericType && it.GetGenericTypeDefinition() == genericType))
        {
            return true;
        }

        if (givenType.IsGenericType && givenType.GetGenericTypeDefinition() == genericType)
            return true;

        Type baseType = givenType.BaseType;
        if (baseType == null) return false;

        return genericType.IsGenericTypeAssignableFrom(baseType);
    }
}