using System;

using System.Collections.Generic;

using System.Reflection;

using System.Reflection.Emit;

using System.Runtime.CompilerServices;

​

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");

​

        // Add IgnoresAccessChecksTo attribute

        var ignoresAccessChecksTo = new CustomAttributeBuilder

        (

            typeof(IgnoresAccessChecksToAttribute).GetConstructor(new Type[] { typeof(string) }),

            new object[] { typeof(List<>).Assembly.GetName().Name }

        );

        assemblyBuilder.SetCustomAttribute(ignoresAccessChecksTo);

​

        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>()));

    }

}

​

// The runtime understands this attribute, but it is not defined in the BCL so you have to define it yourself.

namespace System.Runtime.CompilerServices

{

    [AttributeUsage(AttributeTargets.Assembly, AllowMultiple = true)]

    public class IgnoresAccessChecksToAttribute : Attribute

    {

        public IgnoresAccessChecksToAttribute(string assemblyName)

            => AssemblyName = assemblyName;

​

        public string AssemblyName { get; }

    }

}

​