一、發送端

// 窗體：發送端
public partial class SendForm : Form
{public SendForm(){InitializeComponent();}// 按鈕：發送private void btnSend_Click(object sender, System.EventArgs e){IntPtr hwnd = User32Helper.FindWindow(null, "接收端");int msg = 0x0401;  // 自定義消息IntPtr param = new IntPtr(10);  //自定義參數User32Helper.SendMessage(hwnd, msg, param, IntPtr.Zero);}
}

二、接收端

?

// 窗體：接收端
public partial class ReceiveForm : Form
{public ReceiveForm(){InitializeComponent();}// 重寫方法：窗體消息protected override void WndProc(ref Message m){switch (m.Msg){case 0x0401:  // 自定義消息textBox1.Text = m.WParam.ToString();  //自定義參數break;}base.WndProc(ref m);}
}

三、幫助類

internal class User32Helper
{[DllImport("User32.dll", EntryPoint = "FindWindow")]public static extern IntPtr FindWindow(string lpClassName, string lpWindowName);[DllImport("User32.dll", EntryPoint = "SendMessage")]public static extern IntPtr SendMessage(IntPtr hWnd, int msg, IntPtr wParam, IntPtr lParam);
}