[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
private static extern IntPtr SendMessage(IntPtr hWnd, uint Msg, IntPtr wParam, IntPtr lParam);

using System;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace Sender
{
    public partial class frmSender : Form
    {
        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern IntPtr FindWindow(string lpClassName, string lpWindowName);

        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern IntPtr SendMessage(IntPtr hWnd, uint Msg, IntPtr wParam, IntPtr lParam);

        private const uint WM_COPYDATA = 0x004A;

        [StructLayout(LayoutKind.Sequential)]
        public struct COPYDATASTRUCT
        {
            public IntPtr dwData;
            public int cbData;
            public IntPtr lpData;
        }

        public frmSender()
        {
            InitializeComponent();
        }

        private void btnSend_Click(object sender, EventArgs e)
        {
            string windowName = "Receiver"; // 假設(shè)接收方窗口的標(biāo)題是"Receiver"
            IntPtr hWnd = FindWindow(null, windowName);
            if (hWnd == IntPtr.Zero)
            {
                MessageBox.Show("未找到接收方窗口！");
                return;
            }

            string message = txtMessage.Text; // 假設(shè)有一個(gè)文本框用于輸入消息
            byte[] buffer = System.Text.Encoding.Unicode.GetBytes(message);

            COPYDATASTRUCT cds;
            cds.dwData = IntPtr.Zero;
            cds.cbData = buffer.Length;
            cds.lpData = Marshal.AllocHGlobal(buffer.Length);
            Marshal.Copy(buffer, 0, cds.lpData, buffer.Length);

            SendMessage(hWnd, WM_COPYDATA, IntPtr.Zero, ref cds);

            Marshal.FreeHGlobal(cds.lpData);
        }
    }
}

using System;
using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace Receiver
{
    public partial class frmReceiver : Form
    {
        private const int WM_COPYDATA = 0x004A;

        [StructLayout(LayoutKind.Sequential)]
        public struct COPYDATASTRUCT
        {
            public IntPtr dwData;
            public int cbData;
            [MarshalAs(UnmanagedType.LPWStr)]
            public string lpData;

            // 注意：這里的lpData不能直接使用IntPtr，因?yàn)槲覀冃枰苯釉L(fǎng)問(wèn)字符串?dāng)?shù)據(jù)
            // 在實(shí)際使用中，你可能需要先從IntPtr轉(zhuǎn)換為byte[]，然后再轉(zhuǎn)換為string
            // 但為了簡(jiǎn)化示例，這里直接使用了MarshalAs屬性（注意：這可能需要額外的處理來(lái)確保正確性）
        }

        public frmReceiver()
        {
            InitializeComponent();
        }

        protected override void WndProc(ref Message m)
        {
            if (m.Msg == WM_COPYDATA)
            {
                COPYDATASTRUCT cds = (COPYDATASTRUCT)Marshal.PtrToStructure(m.LParam, typeof(COPYDATASTRUCT));
                lstMessages.Items.Add(cds.lpData); // 假設(shè)有一個(gè)列表框用于顯示接收到的消息
            }
            base.WndProc(ref m);
        }
    }
}