Implementing interface at run-time: get_Value method not implemented

Question

I was trying to define a type at run-time that inherits from a known class and implements an interface.

public class ParentClass
{
}

public interface IImplementMe
{
    double Value{get;set}
}

Here's the code snippet that shows how I try to achieve my goal.

   public class ClassBuilder
   {
    public Type Build()
    {
        try
        {
            AssemblyName assemblyName = new AssemblyName("DataBuilderAssembly");
            AssemblyBuilder assemBuilder = Thread.GetDomain().DefineDynamicAssembly(assemblyName, AssemblyBuilderAccess.Run);
            ModuleBuilder moduleBuilder = assemBuilder.DefineDynamicModule("DataBuilderModule");
            TypeBuilder typeBuilder = moduleBuilder.DefineType("NewClass", TypeAttributes.Class, typeof(ParentClass));
            typeBuilder.AddInterfaceImplementation(typeof(IImplementMe));
            BuildProperty(typeBuilder, "Value", typeof(double));
            Type type = typeBuilder.CreateType();

            return type;
        }
        catch (Exception e)
        {
            return null;
        }

    }

    private void BuildProperty(TypeBuilder typeBuilder, string name, Type type)
    {
        FieldBuilder field = typeBuilder.DefineField("m" + name, type, FieldAttributes.Private);
        PropertyBuilder propertyBuilder = typeBuilder.DefineProperty(name, PropertyAttributes.None, type, null);

        MethodAttributes getSetAttr = MethodAttributes.Public | MethodAttributes.HideBySig;

        MethodBuilder getter = typeBuilder.DefineMethod("get_" + name, getSetAttr, type, Type.EmptyTypes);

        ILGenerator getIL = getter.GetILGenerator();
        getIL.Emit(OpCodes.Ldarg_0);
        getIL.Emit(OpCodes.Ldfld, field);
        getIL.Emit(OpCodes.Ret);

        MethodBuilder setter = typeBuilder.DefineMethod("set_" + name, getSetAttr, null, new Type[] { type });

        ILGenerator setIL = setter.GetILGenerator();
        setIL.Emit(OpCodes.Ldarg_0);
        setIL.Emit(OpCodes.Ldarg_1);
        setIL.Emit(OpCodes.Stfld, field);
        setIL.Emit(OpCodes.Ret);


        propertyBuilder.SetGetMethod(getter);
        propertyBuilder.SetSetMethod(setter);
    }
}

For some reason I get an "get_Value method not implemented" exception on calling typeBuilder.CreateType(). So far unable to see the reason behind it.

Answer 1

The c# implicit interface implementation (by name match) is convenience only; when doing it by hand you need to associate each in the virtual-method table using typeBuilder.DefineMethodOverride, passing in the new (generated) method and the interface method to satisfy. This must done for each method of every interface you want to implement.

Answer 2

Changing your line to:

MethodAttributes getSetAttr = MethodAttributes.Public | 
    MethodAttributes.HideBySig | MethodAttributes.SpecialName | MethodAttributes.Virtual;

Your code then worked for me. (The virtual was required.)