using System;
using System.Reflection;
using System.Reflection.Emit;
using System.Runtime.InteropServices;
using System.Runtime.CompilerServices;


namespace HelloWorld
{
	public delegate void NativeMethodInvoker ();

	class Program
	{
		static void Main(string[] args)
		{
			Test1 ();
		}

		public static void Test1 ()
		{
			Console.WriteLine($"Running {nameof(Test1)}...");

			DynamicMethod testUnmanagedCallersOnly = new DynamicMethod("UnmanagedCallersOnly", null, null, typeof(Program).Module);
			ILGenerator il = testUnmanagedCallersOnly.GetILGenerator();
			il.Emit(OpCodes.Nop);
		    
			il.Emit (OpCodes.Ldc_I4_0);
			il.Emit (OpCodes.Conv_I);

			il.Emit(OpCodes.Call, typeof(Program).GetMethod(nameof (CallThing)));
			il.Emit(OpCodes.Nop);
			il.Emit(OpCodes.Ret);
			var testNativeMethod = (NativeMethodInvoker)testUnmanagedCallersOnly.CreateDelegate(typeof(NativeMethodInvoker));

			testNativeMethod ();
		}

		[DllImport ("Foo", EntryPoint="call_thing")]
		public static extern void CallThing (IntPtr pFn);
	}
}