<Window x:Class="FramworkSender.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:FramworkSender"
        mc:Ignorable="d"
        Title="FramworkSender" Height="450" Width="800">
    <Grid>

        <Button Width="100" Height="100" Content="发送" Click="ButtonBase_OnClick"></Button>

    </Grid>

namespace FramworkSender
{
    /// <summary>
    /// MainWindow.xaml 的交互逻辑
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();

            Loaded += MainWindow_Loaded;
        }

        private void MainWindow_Loaded(object sender, RoutedEventArgs e)
        {
        }


        private void ButtonBase_OnClick(object sender, RoutedEventArgs e)
        {
            // 获取接收窗口的句柄

            IntPtr hwnd = FindWindow(null, "FramworkReceieve");
            if (hwnd == IntPtr.Zero)
            {
                MessageBox.Show("找不到窗口");
            }
            else
            {
                SendMessageString(hwnd, "123");
            }
        }

        #region RegisterWindow

        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern uint RegisterWindowMessage(string lpString);

        private uint _customMessageId;
        #endregion



        #region CopyData

        [DllImport("user32.dll")]
        public static extern IntPtr SendMessage(IntPtr hWnd, int Msg, IntPtr wParam, ref COPYDATASTRUCT lParam);


        [DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)]
        public static extern IntPtr FindWindow(string lpClassName, string lpWindowName);

        public const int WM_COPYDATA = 0x004A;

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

        public static void SendMessageString(IntPtr hWnd, string message)
        {
            if (string.IsNullOrEmpty(message)) return;

            byte[] messageBytes = Encoding.Unicode.GetBytes(message + '\0');

            COPYDATASTRUCT cds = new COPYDATASTRUCT();
            cds.dwData = IntPtr.Zero;
            cds.cbData = messageBytes.Length;
            cds.lpData = Marshal.AllocHGlobal(cds.cbData);
            Marshal.Copy(messageBytes, 0, cds.lpData, cds.cbData);
            try
            {
                var result = SendMessage(hWnd, WM_COPYDATA, IntPtr.Zero, ref cds);
            }
            finally
            {
                //释放分配的内存，即使发生异常也不会泄漏资源
                Marshal.FreeHGlobal(cds.lpData);
            }
        }

        #endregion

    }
}

<Window x:Class="FramworkReceieve.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:FramworkReceieve"
        mc:Ignorable="d"
        Title="FramworkReceieve" Height="450" Width="800">
    <Grid>

        <StackPanel Orientation="Horizontal">
            <TextBlock Text="接收到的数据:"/>
            <TextBlock Text="" x:Name="txtMessage"/>
        </StackPanel>

        <Button Height="100" Width="100" Content="清空" Click="ButtonBase_OnClick"></Button>



    </Grid>
</Window>

    /// <summary>
    /// MainWindow.xaml 的交互逻辑
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            Loaded += MainWindow_Loaded;
        }
        private uint _customMessageId;

        private HwndSource _hwndSource;
        private void MainWindow_Loaded(object sender, RoutedEventArgs e)
        {
            _customMessageId = RegisterWindowMessage("MyApp");

            // 获取窗口句柄并添加消息钩子
            _hwndSource = PresentationSource.FromVisual(this) as HwndSource;
            _hwndSource?.AddHook(WndProc);
        }

        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 16)]
        public string content;


        private IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
        {


            #region CopyData

            if (msg == WM_COPYDATA)
            {
                COPYDATASTRUCT cds = (COPYDATASTRUCT)Marshal.PtrToStructure(lParam, typeof(COPYDATASTRUCT));
                string receivedMessage = Marshal.PtrToStringUni(cds.lpData);

                this.Dispatcher.Invoke(() =>
                {
                    txtMessage.Text = receivedMessage;
                });

                handled = true;
            }

            #endregion



            return IntPtr.Zero;
        }


        #region  RegisterWindows

        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern uint RegisterWindowMessage(string lpString);


        #endregion


        #region CopyData


        public const int WM_COPYDATA = 0x004A;

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

        #endregion



        protected override void OnClosed(EventArgs e)
        {
            _hwndSource?.RemoveHook(WndProc);
            base.OnClosed(e);
        }

        private void ButtonBase_OnClick(object sender, RoutedEventArgs e)
        {
            txtMessage.Text = "";
        }
    }