微软实现的获取进程主窗口句柄代码

public class MyProcess
{
private bool haveMainWindow = false;
private IntPtr mainWindowHandle = IntPtr.Zero;
private int processId = 0;

private delegate bool EnumThreadWindowsCallback(IntPtr hWnd, IntPtr lParam);

public IntPtr GetMainWindowHandle(int processId)
{
if (!this.haveMainWindow)
{
this.mainWindowHandle = IntPtr.Zero;
this.processId = processId;
EnumThreadWindowsCallback callback = new EnumThreadWindowsCallback(this.EnumWindowsCallback);
EnumWindows(callback, IntPtr.Zero);
GC.KeepAlive(callback);

this.haveMainWindow = true;
}
return this.mainWindowHandle;
}

private bool EnumWindowsCallback(IntPtr handle, IntPtr extraParameter)
{
int num;
GetWindowThreadProcessId(new HandleRef(this, handle), out num);
if ((num == this.processId) && this.IsMainWindow(handle))
{
this.mainWindowHandle = handle;
return false;
}
return true;
}

private bool IsMainWindow(IntPtr handle)
{
return (!(GetWindow(new HandleRef(this, handle), 4) != IntPtr.Zero) && IsWindowVisible(new HandleRef(this, handle)));
}

[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
public static extern bool EnumWindows(EnumThreadWindowsCallback callback, IntPtr extraData);

[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
public static extern int GetWindowThreadProcessId(HandleRef handle, out int processId);

[DllImport("user32.dll", CharSet = CharSet.Auto, ExactSpelling = true)]
public static extern IntPtr GetWindow(HandleRef hWnd, int uCmd);

[DllImport("user32.dll", CharSet = CharSet.Auto)]
public static extern bool IsWindowVisible(HandleRef hWnd);
}