C# WndProc 方法未收到预期的消息类型

如何解决C# WndProc 方法未收到预期的消息类型

我一直在尝试使用其记录的 copYDATA API 与另一个软件进行通信。用户 Xanotos 对 in this question I asked 非常有帮助，它的发送方法已排序并且工作正常。我遇到的问题是接收 WndProc 方法似乎没有捕捉到预期的响应。这是 COPYDATA API 文档的链接以供参考。

目前的方法如下。测试表明 WndProc 确实收到消息，但不是我期望的消息，即 struct 取决于发送的消息。

声明：

 [DllImport("User32.dll",SetLastError = true,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,int wParam,ref copYDATASTRUCT lParam);

    [StructLayout(LayoutKind.Sequential)]
    public struct copYDATASTRUCT
    {
        public IntPtr dwData;    // Any value the sender chooses.  Perhaps its main window handle?
        public int cbData;       // The count of bytes in the message.
        public IntPtr lpData;    // The address of the message.
    }
    public struct ExternalGetPositionType
    {
        public double X;
        public double Y;
        public double Z;
        public double W;
    }
    const int WM_copYDATA = 0x004A;
    const int EXTERNAL_CD_COMMAND_RUN_ASYNC = 0x8001;
    const int EXTERNAL_CD_GET_POSITION_PCS = 0x8011;
    const int EXTERNAL_CD_GET_POSITION_MCS = 0x8012;

发送方法（这些都可以正常工作并返回真）：

public static IntPtr RunAsync(IntPtr hwnd,string str)
    {
        // We have to add a \0 terminator,so len + 1 / len + 2 for Unicode
        int len = Encoding.Default.GetByteCount(str);
        var buff = new byte[len + 1]; // len + 2 for Unicode
        Encoding.Default.GetBytes(str,str.Length,buff,0);

        IntPtr ret;

        GCHandle h = default(GCHandle);

        try
        {
            h = GCHandle.Alloc(buff,GCHandleType.Pinned);

            var cds = new copYDATASTRUCT();
            cds.dwData = (IntPtr)EXTERNAL_CD_COMMAND_RUN_ASYNC;
            cds.lpData = h.AddrOfPinnedobject();
            cds.cbData = buff.Length;

            ret = SendMessage(hwnd,WM_copYDATA,ref cds);
        }
        finally
        {
            if (h.IsAllocated)
            {
                h.Free();
            }
        }

        return ret;
    }

    public static IntPtr GetPosition(IntPtr hwnd,bool pcs,ExternalGetPositionType position)
    {
        // We cheat here... It is much easier to pin an array than to copy around a struct
        var positions = new[]
        {
    position
};

        IntPtr ret;

        GCHandle h = default(GCHandle);

        try
        {
            h = GCHandle.Alloc(positions,GCHandleType.Pinned);

            var cds = new copYDATASTRUCT();
            cds.dwData = pcs ? (IntPtr)EXTERNAL_CD_GET_POSITION_PCS : (IntPtr)EXTERNAL_CD_GET_POSITION_MCS;
            cds.lpData = h.AddrOfPinnedobject();
            cds.cbData = Marshal.SizeOf<ExternalGetPositionType>();

            ret = SendMessage(hwnd,ref cds);
        }
        finally
        {
            if (h.IsAllocated)
            {
                h.Free();
            }
        }

        return ret;
    }

WndProc 方法 - 这是事情没有按预期工作的地方。调用 if(m.Msg == WM_copYDATA) 时，GetPosition 永远不会返回 true。

protected override void WndProc(ref Message m)
    {
        if (m.Msg == WM_copYDATA) //this does not execute
        {
            copYDATASTRUCT cds = Marshal.PtrToStructure<copYDATASTRUCT>(m.LParam);
            label5.Text = "message received";
            if (cds.dwData == (IntPtr)EXTERNAL_CD_COMMAND_RUN_ASYNC)
            {
                label5.Text = "norMAL";
                string str = Marshal.PtrToStringAnsi(cds.lpData);

                Debug.WriteLine($"EXTERNAL_CD_COMMAND_RUN_ASYNC: {str}");
                toolStripStatusLabel1.Text = $"COMMAND";
                m.Result = (IntPtr)100; // If you want to return a value
            }
            else if (cds.dwData == (IntPtr)EXTERNAL_CD_GET_POSITION_PCS) //this does not execute
            {
                label5.Text = "MSC";
                if (cds.cbData >= Marshal.SizeOf<ExternalGetPositionType>())
                {
                    var position = Marshal.PtrToStructure<ExternalGetPositionType>(cds.lpData);

                    Debug.WriteLine($"EXTERNAL_CD_GET_POSITION_PCS: X = {position.X},Y = {position.Y},Z = {position.Z},W = {position.W}");
                    toolStripStatusLabel1.Text = $"External MCS = {position.X}";
                    label4.Text = position.X.ToString();

                    m.Result = (IntPtr)200;
                }
                else
                {
                    m.Result = (IntPtr)0;
                }
            }
            else if (cds.dwData == (IntPtr)EXTERNAL_CD_GET_POSITION_MCS) //this does not execute
            {
                label5.Text = "MSC"; //this does not execute
                if (cds.cbData >= Marshal.SizeOf<ExternalGetPositionType>())
                {
                    var position = Marshal.PtrToStructure<ExternalGetPositionType>(cds.lpData);

                    Debug.WriteLine($"EXTERNAL_CD_GET_POSITION_MCS: X = {position.X},W = {position.W}");
                    toolStripStatusLabel1.Text = $"External MCS = {position.X}";
                    label4.Text = position.X.ToString(); 

                    m.Result = (IntPtr)300;
                }
                else
                {
                    m.Result = (IntPtr)0;
                }
            }

            return;
        }
        MessageBox.Show(m.Msg.ToString()); //this DOES execute
        
        base.WndProc(ref m);
    }

两个程序都是 32 位的。

知道为什么我没有收到预期的 Msg 吗？

解决方法

您提供的文档不清楚，但您似乎需要将 wParam 设置为接收窗口句柄才能接收响应数据。

在第 3 页的底部有一个例子：

::SendMessage(m_pWnd->GetSafeHwnd(),WM_COPYDATA,(WPARAM)this->GetSafeHwnd(,(LPARAM)&MyCDS);

而你的代码有这个：

ret = SendMessage(hwnd,ref cds);

相反，你需要

ret = SendMessage(hwnd,this.Handle,ref cds);

您必须还将 wParam 上的 SendMessage 重新定义为 IntPtr。在任何情况下都是错误的，可能只是因为您使用的是 32 位。