using System;using System.Collections.Generic;using System.Text; namespace ConsoleApplication1{    class Program    {        static void Main(string[] args)        {            MessageBoxA(0,"Hello World!","My Message Box",0);            Console.WriteLine("Over");            Console.Read();        }         #region C++        [System.Runtime.InteropServices.DllImport("user32.dll")]        public static extern int MessageBoxA(                int b,                [System.Runtime.InteropServices.MarshalAs(System.Runtime.InteropServices.UnmanagedType.LPStr)]string m,                [System.Runtime.InteropServices.MarshalAs(System.Runtime.InteropServices.UnmanagedType.LPStr)]string c,                int type            );        #endregion    }}

 P/Invoke Tutorial: Basics (Part 1):

可以从这里下载现成的开发结构。