如何将自定义消息从 C++ MFC 发送到 WPF C# 应用程序？

Question

我需要将自定义消息/通知从 MFC(C++) 发送到 WPF(C#) 应用程序。 互联网上有一些关于从 C# 到 C++ 应用程序发送消息的主题。 我试图实现我的案例，然后是那些文章，但无法接收来自 WPF 的消息。

下面给出了我尝试过的所有内容：

从 MFC 应用程序中，我尝试使用 PostMessage 和 SendMessage 发送消息 但是这些都不能从 WPF 应用程序接收。

UINT deviceConnected = 0;
deviceConnected = RegisterWindowMessage(L"DEVICE_CONNECTED");
HWND dstWnd = (HWND)GetProp(GetDesktopWindow(), L"DEVICE_CONNECTED_HWND");

const char* message = "This is a custom message";
::PostMessage(dstWnd, deviceConnected, 0, (LPARAM)(LPCTSTR)message);
::SendMessage(dstWnd, deviceConnected, 0, (LPARAM)(LPCTSTR)message);

我也尝试过使用 WM_COPYDATA：

LPCTSTR lpszString = (LPCTSTR)L"This is second message";
COPYDATASTRUCT cds;
cds.dwData = 0;
cds.cbData = sizeof(TCHAR) * (_tcslen(lpszString) + 1);
cds.lpData = (PVOID)lpszString;
::PostMessage(dstWnd, WM_COPYDATA, 0, (LPARAM)(LPVOID)&cds); 
::SendMessage(dstWnd, WM_COPYDATA, 0, (LPARAM)(LPVOID)&cds);

以下是 WPF 代码示例：

[DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)]
static extern uint RegisterWindowMessage(string lpString);
private UInt32 deviceAttachedEvent = 0;
const int WM_COPYDATA = 0x4A;
    
protected override void OnSourceInitialized(EventArgs e)
{
    base.OnSourceInitialized(e);
    HwndSource hwndSource = HwndSource.FromVisual(this) as HwndSource;
    if (hwndSource != null)
    {
        hwndSource.AddHook(new HwndSourceHook(WndProc));
    }
}

private IntPtr WndProc(IntPtr hwnd, int msgId, IntPtr wParam, IntPtr lParam, ref bool handled)
{
    IntPtr result = IntPtr.Zero;

    //if the deviceAttachedEvent message id has not been registered...
    if (deviceAttachedEvent == 0)
        deviceAttachedEvent  = RegisterWindowMessage("DEVICE_CONNECTED");

    if ((UInt32)msgId == deviceAttachedEvent )
    {
        //string msg = Marshal.PtrToStringAuto(lParam);
        Console.WriteLine("Received message from MFC");
        //Console.WriteLine(msg);
    }

    if (msgId == WM_COPYDATA)
    {
        COPYDATASTRUCT cds = new COPYDATASTRUCT();
        cds = (COPYDATASTRUCT)Marshal.PtrToStructure(lParam,typeof(COPYDATASTRUCT));
        if (cds.cbData > 0)
        {
            byte[] data = new byte[cds.cbData];
            Marshal.Copy(cds.lpData, data, 0, cds.cbData);
            Encoding unicodeStr = Encoding.ASCII;
            char[] myString = unicodeStr.GetChars(data);
            string returnText = new string(myString);
            MessageBox.Show("ACK Received: " + returnText);
        }
    }
    
    return result;
}

提前致谢。

Answer 1

我可以使用代码获取 C++ 项目发送的消息（deviceAttachedEvent 和 WM_COPYDATA）。 我使用FindWindow(NULL,L"WPFwindow name") 来获取hwnd 句柄，而不是GetProp，因此请确保您拥有正确的窗口句柄。您可以使用EnumPropsEx 来测试您是否拥有"DEVICE_CONNECTED_HWND" 的属性

对于窗口消息deviceConnected： 你在当前进程中发送一个指针，另一个进程通常没有权限直接访问这个地址。需要使用ReadProcessMemory读取该地址中的字符串数据。

另外，请注意项目的字符集。如果字符集是 UNICODE，L"***" 不需要强制转换为 LPCTSTR，如果字符集是多字节字符集，则使用 "***"。或者使用TEXT("") 宏。

另外，您发送了一个宽字节字符串L"This is second message"，然后在读取时设置Encoding.ASCII，这将截断字符串，如：

所以我的示例是： C++：

#include <windows.h>
#include <iostream>
#include <tchar.h>
int main()
{
    UINT deviceConnected = 0;
    deviceConnected = RegisterWindowMessage(L"DEVICE_CONNECTED");
    HWND dstWnd = FindWindow(NULL,L"MainWindow");

    const wchar_t* message = TEXT("This is a custom message");
    ::SendMessage(dstWnd, deviceConnected, 0, (LPARAM)(LPCTSTR)message);

    LPCTSTR lpszString = TEXT("This is second message");
    COPYDATASTRUCT cds;
    cds.dwData = 0;
    cds.cbData = sizeof(TCHAR) * (_tcslen(lpszString) + 1);
    cds.lpData = (PVOID)lpszString;

    ::SendMessage(dstWnd, WM_COPYDATA, 0, (LPARAM)(LPVOID)&cds);

}

在 wpf 中：

   private IntPtr WndProc(IntPtr hwnd, int msgId, IntPtr wParam, IntPtr lParam, ref bool handled)
    {
        IntPtr result = IntPtr.Zero;

        //if the deviceAttachedEvent message id has not been registered...
        if (deviceAttachedEvent == 0)
            deviceAttachedEvent = RegisterWindowMessage("DEVICE_CONNECTED");

        if ((UInt32)msgId == deviceAttachedEvent)
        {
            //OpenProcess + PROCESS_VM_READ
            //ReadProcessMemory + lParam
            Console.WriteLine("Received message from MFC");
        }

        if (msgId == WM_COPYDATA)
        {
            COPYDATASTRUCT cds = new COPYDATASTRUCT();
            cds = (COPYDATASTRUCT)Marshal.PtrToStructure(lParam, typeof(COPYDATASTRUCT));
            if (cds.cbData > 0)
            {
                byte[] data = new byte[cds.cbData];
                Marshal.Copy(cds.lpData, data, 0, cds.cbData);
                Encoding unicodeStr = Encoding.Unicode;
                char[] myString = unicodeStr.GetChars(data);
                string returnText = new string(myString);
                MessageBox.Show("ACK Received: " + returnText);
            }
        }

        return result;
    }