使用 SendMessage WM_COPYDATA 发送双精度数组

Question

我在将双精度数组从一个应用程序发送到另一个应用程序时遇到问题（均为 c#）。

我尝试像这样格式化CopyData Struct：

    [StructLayout(LayoutKind.Sequential)]
    public struct CopyDataStruct
    {
        public IntPtr dwData;
        public int cbData;
        [MarshalAs(UnmanagedType.ByValArray, ArraySubType = UnmanagedType.R8)]
        public double[] lpData;
    }

在Sender Application 我这样填充结构：

            double[] a = new double[2] { 1.0, 2.0 };
            int size = Marshal.SizeOf(typeof(double)) * a.Count();

            CopyDataStruct copyDataStruct;
            copyDataStruct.dwData = IntPtr.Zero;
            copyDataStruct.lpData = a;
            copyDataStruct.cbData = size;

            int result = SendMessage(hWnd, WM_COPYDATA, 0, ref copyDataStruct);

在Receiver Application，我试试这个：

    private IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
    {
        switch (msg)
        {
            case (int)WINMESSAGES.WM_COPYDATA:
                CopyDataStruct cp = (CopyDataStruct)Marshal.PtrToStructure(lParam, typeof(CopyDataStruct));

                break;
        }

        return IntPtr.Zero;
    }

但在cp.lpDat中，值来自null。不知道是发错了还是收错了。请帮忙，谢谢。

Answer 1

您需要使用本机内存。像这样通过 C# double[] 是行不通的。它将被垃圾收集（哎呀，它甚至没有在 C# 中分配 - 它只是在堆栈中）。您可以使用不安全/固定关键字固定对象或使用AllocHGlobal。

这是我从互联网上窃取的一些代码。演示发送部分：

    // Marshal the managed struct to a native block of memory.
    var myStruct = new double[2] { 1.0, 2.0 };
    int myStructSize = Marshal.SizeOf(myStruct); 
    IntPtr pMyStruct = Marshal.AllocHGlobal(myStructSize);
    try
    {
        Marshal.StructureToPtr(myStruct, pMyStruct, true);

        COPYDATASTRUCT cds = new COPYDATASTRUCT();
        cds.cbData = myStructSize;
        cds.lpData = pMyStruct;

        // Send the COPYDATASTRUCT struct through the WM_COPYDATA message to 
        // the receiving window. (The application must use SendMessage, 
        // instead of PostMessage to send WM_COPYDATA because the receiving 
        // application must accept while it is guaranteed to be valid.)
        NativeMethod.SendMessage(hTargetWnd, WM_COPYDATA, this.Handle, ref cds);

        int result = Marshal.GetLastWin32Error();
        if (result != 0)
        {
            MessageBox.Show(String.Format(
                "SendMessage(WM_COPYDATA) failed w/err 0x{0:X}", result));
        }
    }
    finally
    {
        Marshal.FreeHGlobal(pMyStruct);
    }

拍摄：http://code.msdn.microsoft.com/windowsdesktop/CSReceiveWMCOPYDATA-dbbc7ed7