using System;

using System.Collections.Generic;

using System.Reflection;

using System.Reflection.Emit;

public class Program

{

    public static void Main()

    {

        // EXAMPLE 1

        var method1 = new DynamicMethod("GetUnderlyingArray", typeof(int[]), new[] { typeof(List<int>) }, typeof(List<int>), true);

​

        var ilGenerator1 = method1.GetILGenerator();

​

        ilGenerator1.Emit(OpCodes.Ldarg_0);

        ilGenerator1.Emit(OpCodes.Ldfld, typeof(List<int>).GetField("_items", BindingFlags.NonPublic | BindingFlags.Instance));

        ilGenerator1.Emit(OpCodes.Ret);

​

        var arrayGetter1 = (Func<List<int>, int[]>)method1.CreateDelegate(typeof(Func<List<int>, int[]>));

        Console.WriteLine("Example 1");

        Console.WriteLine(arrayGetter1.Invoke(new List<int>()));

        // EXAMPLE 2

        var assemblyName = new AssemblyName("Example");

        var assemblyBuilder = AssemblyBuilder.DefineDynamicAssembly(assemblyName, AssemblyBuilderAccess.Run);

        var dynamicModule = assemblyBuilder.DefineDynamicModule(assemblyName.Name + ".dll");

        var type = dynamicModule.DefineType("GetUnderlyingArrayClass");

        var method2 = type.DefineMethod("GetUnderlyingArray", MethodAttributes.Public | MethodAttributes.HideBySig | MethodAttributes.Static, typeof(int[]), new[] { typeof(List<int>) });

        var ilGenerator2 = method2.GetILGenerator();

        ilGenerator2.Emit(OpCodes.Ldarg_0);

        ilGenerator2.Emit(OpCodes.Ldfld, typeof(List<int>).GetField("_items", BindingFlags.NonPublic | BindingFlags.Instance));

        ilGenerator2.Emit(OpCodes.Ret);

        type.CreateType();

        var arrayGetter2 = (Func<List<int>, int[]>)type.GetMethod("GetUnderlyingArray").CreateDelegate(typeof(Func<List<int>, int[]>));

        Console.WriteLine("Example 2");

        Console.WriteLine(arrayGetter2.Invoke(new List<int>()));

    }

}