C# 使用WM_COPYDATA传输数据（两个窗体间通信）

//发送方


using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Runtime.InteropServices;
using System.Text;
using System.Windows.Forms;

namespace ExeToWinform
{
    public partial class Form2 : Form
    {
        public Form2()
        {
            InitializeComponent();
        }

         const int WM_COPYDATA = 0x004A;
        public struct COPYDATASTRUCT
        {
            public IntPtr dwData;
            public int cData;
            [MarshalAs(UnmanagedType.LPStr)]
            public string lpData;
        }
        
        [DllImport("User32.dll")]
        public static extern int SendMessage(int hwnd, int msg, int wParam, ref COPYDATASTRUCT IParam);
        [DllImport("User32.dll")]
        public static extern int FindWindow(string lpClassName, string lpWindowName);
        
        private void button1_Click(object sender, EventArgs e)
        {
            int WINDOW_HANDLE = FindWindow(null, "接受窗口");
            if (WINDOW_HANDLE!=0)
            {
                byte[] arr = System.Text.Encoding.Default.GetBytes(textBox1.Text);
                int len = arr.Length;
                COPYDATASTRUCT cdata;
                cdata.dwData = (IntPtr)100;
                cdata.lpData = textBox1.Text;
                cdata.cData = len + 1;
                SendMessage(WINDOW_HANDLE, WM_COPYDATA, 0, ref cdata);
            }
        }

    }
}

//接收方

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Runtime.InteropServices;
using System.Text;
using System.Windows.Forms;

namespace TestPtr
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }



        const int WM_COPYDATA = 0x004A;//WM_COPYDATA消息的主要目的是允许在进程间传递只读数据。
        //Windows在通过WM_COPYDATA消息传递期间，不提供继承同步方式。
        //其中,WM_COPYDATA对应的十六进制数为0x004A
        public struct COPYDATASTRUCT
        {
            public IntPtr dwData;
            public int cData;
            [MarshalAs(UnmanagedType.LPStr)]
            public string lpData;
        }

        /// <summary>
        /// 接收消息
        /// </summary>
        /// <param name="m"></param>
        protected override void DefWndProc(ref Message m)
        {
            switch (m.Msg)
            {
                case WM_COPYDATA:
                    COPYDATASTRUCT cdata = new COPYDATASTRUCT();
                    Type mytype = cdata.GetType();
                    cdata = (COPYDATASTRUCT)m.GetLParam(mytype);
                    this.label1.Text = cdata.lpData;
                    break;
                default:
                    base.DefWndProc(ref m);
                    break;
            }
        }

    }
}

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