使加载了加载库的 DLL 在前台显示其窗口

Question

我为SAP Business One开发了一个附加组件，作为C# Windows Forms应用程序。

在这个附加组件中，使用LoadLibraryEx，我加载了一个用 C++ 编写的本机非托管 DLL(如果我错了，请纠正我(。

该加载项调用 DLL 的方法，方式如下：

[DllImport("kernel32.dll", SetLastError = true)]
public static extern IntPtr LoadLibraryEx(string lpFileName, IntPtr hReservedNull, LoadLibraryFlags dwFlags);
[DllImport("kernel32.dll", CharSet = CharSet.Ansi)]
public static extern IntPtr GetProcAddress(IntPtr hModule, string lpProcName);
[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
private delegate int _MyDllMethod();
//...
//load library
var handle = LoadLibraryEx(libPath, IntPtr.Zero, 0x00000008 /*LOAD_WITH_ALTERED_SEARCH_PATH*/);
//invoke method
Type delegateFunType = typeof(_MyDllMethod);
IntPtr funAddr = GetProcAddress(handle, delegateFunType.Name);
var fun = Convert.ChangeType(Marshal.GetDelegateForFunctionPointer(funAddr, delegateFunType), delegateFunType);
int result = fun.Invoke(); //now a window appears

此方法将打开一个用户与之交互的窗口。

一切正常，除了这样的窗口在任务栏中最小化，而我需要它作为活动窗口出现在forground中。我该如何解决这个问题？

Answer 1

最后我发现了这个技巧：启动一个并行线程，该线程查找将由DLL打开的窗口，并使用Windows API函数将其置于前台：

[DllImport("kernel32.dll", SetLastError = true)]
public static extern IntPtr LoadLibraryEx(string lpFileName, IntPtr hReservedNull, LoadLibraryFlags dwFlags);
[DllImport("kernel32.dll", CharSet = CharSet.Ansi)]
public static extern IntPtr GetProcAddress(IntPtr hModule, string lpProcName);
[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
private delegate int _MyDllMethod();
[DllImport("User32.dll", CharSet = CharSet.Unicode)]
public static extern IntPtr FindWindow(String lpClassName, String lpWindowName);
[DllImport("User32.dll")]
public static extern bool SetForegroundWindow(IntPtr hWnd);
[DllImport("User32.dll")]
private static extern bool ShowWindow(IntPtr handle, int nCmdShow);
[DllImport("User32.dll")]
private static extern bool IsIconic(IntPtr handle);
[DllImport("User32.dll")]
private static extern void keybd_event(byte bVk, byte bScan, uint dwFlags, int dwExtraInfo);
private const int ALT = 0xA4;
private const int EXTENDEDKEY = 0x1;
private const int KEYUP = 0x2;
private const int SW_RESTORE = 9;
//...
//launch a parallel thread that looks for library window
//and brings it to the foreground
ThreadPool.QueueUserWorkItem(delegate {
bool windowFound = false;
int attempts = 0;
while (!windowFound && attempts < 10)
{
attempts++;
//check frequently
Thread.Sleep(200);
//look for the window using its class name
IntPtr handle = FindWindow("DllWindowClassName", null);
//check it is a running process
if (handle != IntPtr.Zero)
{
bool success = false;
//if window is minimized to icon
if (IsIconic(handle))
{
//then show it
success = ShowWindow(handle, SW_RESTORE);
}
//bring window to front
success = SetForegroundWindow(handle);
//once done, this thread can terminate
if (success)
{
windowFound = true;
}
else
{
//in case of failure, try this hack
//simulate a key press and release (hack for SetForegroundWindow to work)
keybd_event((byte)ALT, 0x45, EXTENDEDKEY | 0, 0);
keybd_event((byte)ALT, 0x45, EXTENDEDKEY | KEYUP, 0);
//bring window to front
success = SetForegroundWindow(handle);
//once done, this thread can terminate
if (success)
{
windowFound = true;
}
}
}
}
}, null);
//load library
var handle = LoadLibraryEx(libPath, IntPtr.Zero, 0x00000008 /*LOAD_WITH_ALTERED_SEARCH_PATH*/);
//invoke method
Type delegateFunType = typeof(_MyDllMethod);
IntPtr funAddr = GetProcAddress(handle, delegateFunType.Name);
var fun = Convert.ChangeType(Marshal.GetDelegateForFunctionPointer(funAddr, delegateFunType), delegateFunType);
int result = fun.Invoke(); //now a window appears

您可以使用FindWindow、传递窗口标题，然后使用GetClassName来发现窗口类名。类名比标题更可靠，标题可以随语言和时间而变化。