DefWndProc方法内GetLParam方法异常（System.ArgumentOutOfRangeException was unhandled）

Question

我要做一个进程间通信的功能，但是在GetLParam处出现了System.ArgumentOutOfRangeException，不知道这个是什么原因。

发送方（控制台程序）代码：

using System;
using System.Collections.Generic;
using System.Text;
using System.Threading;
using System.Runtime.InteropServices;  //[DllImport("user32.dll")]中DllImport的命名空间
using DllTest;

namespace Sender
{
    class Program
    {
        static void Main(string[] args)
        {
            string strDlgTitle = "Receiver";

            //接收端的窗口句柄
            IntPtr hwndRecvWindow = ImportFromDLL.FindWindow(null, strDlgTitle);
            if (hwndRecvWindow == IntPtr.Zero)
            {
                Console.WriteLine("请先启动接收消息程序");
                return;
            }

            //自己的窗口句柄
            IntPtr hwndSendWindow = ImportFromDLL.GetConsoleWindow();
            if (hwndSendWindow == IntPtr.Zero)
            {
                Console.WriteLine("获取自己的窗口句柄失败，请重试");
                return;
            }

            for (int i = 0; i < 10; i++)
            {
                string strText = DateTime.Now.ToString();
                //填充COPYDATA结构
                DllTest.DllTest.COPYDATASTRUCT copydata = new DllTest.DllTest.COPYDATASTRUCT();
                copydata.dwData = hwndRecvWindow;//Add 2014-12-03
                copydata.cbData = Encoding.Default.GetBytes(strText).Length; //长度 注意不要用strText.Length;
                copydata.lpData = strText;                                   //内容

                ImportFromDLL.SendMessage(hwndRecvWindow, ImportFromDLL.WM_COPYDATA, 2, ref copydata);

                Console.WriteLine(strText);
                Thread.Sleep(1000);
            }

        }
    }

    public class ImportFromDLL
    {
        public const int WM_COPYDATA = 0x004A;


        [DllImport("User32.dll")]
        public static extern int SendMessage(
            IntPtr hWnd,　　　           
            int Msg,　　　               
            int wParam,　                
            ref DllTest.DllTest.COPYDATASTRUCT lParam
        );

        [DllImport("User32.dll", EntryPoint = "FindWindow")]
        public static extern IntPtr FindWindow(string lpClassName, string lpWindowName);

        [DllImport("Kernel32.dll", EntryPoint = "GetConsoleWindow")]
        public static extern IntPtr GetConsoleWindow();
    }
}

接收方（windows窗体程序）代码：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Collections;
using System.Runtime.InteropServices;
using DllTest;

namespace Receiver
{
    public partial class Receiver : Form
    {
        const int WM_COPYDATA = 0x004A;
        public Receiver()
        {
            InitializeComponent();
        }

        protected override void DefWndProc(ref Message m)
        {
            switch (m.Msg)
            {
                //接收自定义消息USER，并显示其参数
                case WM_COPYDATA:
                    DllTest.DllTest.COPYDATASTRUCT mystr = new DllTest.DllTest.COPYDATASTRUCT();
                    Type mytype = mystr.GetType();
                    mystr = (DllTest.DllTest.COPYDATASTRUCT)m.GetLParam(mytype);
                    this.textBox1.Text = mystr.lpData;
                    break;
                default:
                    base.DefWndProc(ref m);
                    break;
            }
        }
    }
}

它们共用的自定义结构体代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Runtime.InteropServices;

namespace DllTest
{
    public class DllTest
    {
        //启用非托管代码
        [StructLayout(LayoutKind.Sequential)]
        public struct COPYDATASTRUCT
        {
            public IntPtr dwData;
            public int cbData;
            [MarshalAs(UnmanagedType.LPStr)]
            public string lpData;
        }
    }
}

自定义的结构体代码生成了一个dll，并且已经在发送方和接收方中引入了，现在出现了System.ArgumentOutOfRangeException异常提示，请教下这个问题怎么解决？谢谢！

Answer 1

问题解决了，我改了下面一段代码

copydata.cbData = Encoding.Default.GetBytes(strText).Length + 1;

也就是给发送的字符串按字节计的长度上加了1。

但是不知道为什么这样做，那个异常就没了。

期待各位详解

Answer 2

你好：

原因是要发送的字节数组最后要以null结尾，最后应该多出一位"\0"。

参考这篇帖子：

http://stackoverflow.com/questions/6779731/c-sharp-using-sendmessage-problem-with-wm-copydata

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Answer 3

谢谢解答！