c#, reflection.emit trying hard

I wanted to try how the System.Reflection.Emit works, but eventually I've stack with some problem. I wanted to create (using Emit) some simple class, like this:

using System;

namespace emit
{
    class Builder
    {
        private String name;

        public Builder(String builderName)
        {
            name = builderName;
        }

        public override int GetHashCode()
        {
            return name.GetHashCode();
        }

        public override string ToString()
        {
            return this.name;
        }
    }
}

I've been through some tutorials and I've managed to create dynamic library. I've saved that library on my disk and then loaded it using reflection. I was able to filter it's types, constructors and methods. I also succesfully invoked the constructor passing desired string. Yet, there's a problem when I'm trying to invoke any of methods- System.Reflection.TargetInvocationException is thrown.

Here's how I implemented GetHashCode():

MethodBuilder mHashCode = tBuilder.DefineMethod("GetHashCode",
                MethodAttributes.Public | MethodAttributes.HideBySig | MethodAttributes.Virtual,
                CallingConventions.HasThis, typeof(System.Int32), null);
            mHashCode.SetImplementationFlags(MethodImplAttributes.Managed);
            ILGenerator mHashGenerator = mHashCode.GetILGenerator();

            MethodInfo defaultHashCode = typeof(object).GetMethod("GetHashCode");

            mHashGenerator.Emit(OpCodes.Ldfld, simpleName);
            mHashGenerator.Emit(OpCodes.Callvirt, defaultHashCode);
            mHashGenerator.Emit(OpCodes.Ret);

tBuilder is TypeBuilder that I'm creating.

After saving the assembly and looking into with ILDSASM it's like:

And the EditModule.dll:

Unfortunately, this method won't invoke. Here's the code:

                Type dType = asm.GetTypes()[0];
                ConstructorInfo dConstructor = dType.GetConstructor(new Type[] { typeof(string) });
                object dObject = dConstructor.Invoke(new object[] { "Pawel" });
                MethodInfo[] dMethods = dType.GetMethods();
                foreach(var mi in dMethods)
                {
                    Console.WriteLine(mi.Name);
                }
                //method with `0` index is `GetHashCode()`
                dMethods[0].Invoke(dObject, null);

Does anyone have an idea what I might be doing wrong?