public class User32API {     private static Hashtable processWnd = null;     public delegate bool WNDENUMPROC(IntPtr hwnd, uint lParam);     static User32API()     {         if (processWnd == null)         {             processWnd = new Hashtable();         }     }     [DllImport("user32.dll", EntryPoint = "EnumWindows", SetLastError = true)]     public static extern bool EnumWindows(WNDENUMPROC lpEnumFunc, uint lParam);     [DllImport("user32.dll", EntryPoint = "GetParent", SetLastError = true)]     public static extern IntPtr GetParent(IntPtr hWnd);     [DllImport("user32.dll", EntryPoint = "GetWindowThreadProcessId")]     public static extern uint GetWindowThreadProcessId(IntPtr hWnd, ref uint lpdwProcessId);     [DllImport("user32.dll", EntryPoint = "IsWindow")]     public static extern bool IsWindow(IntPtr hWnd);     [DllImport("kernel32.dll", EntryPoint = "SetLastError")]     public static extern void SetLastError(uint dwErrCode);     public static IntPtr GetCurrentWindowHandle()     {         IntPtr ptrWnd = IntPtr.Zero;         uint uiPid = (uint)Process.GetCurrentProcess().Id;  // 当前进程 ID         object objWnd = processWnd[uiPid];         if (objWnd != null)         {             ptrWnd = (IntPtr)objWnd;             if (ptrWnd != IntPtr.Zero && IsWindow(ptrWnd))  // 从缓存中获取句柄             {                 return ptrWnd;             }             else             {                 ptrWnd = IntPtr.Zero;             }         }         bool bResult = EnumWindows(new WNDENUMPROC(EnumWindowsProc), uiPid);         // 枚举窗口返回 false 并且没有错误号时表明获取成功         if (!bResult && Marshal.GetLastWin32Error() == 0)         {             objWnd = processWnd[uiPid];             if (objWnd != null)             {                 ptrWnd = (IntPtr)objWnd;             }         }         return ptrWnd;     }     private static bool EnumWindowsProc(IntPtr hwnd, uint lParam)     {         uint uiPid = 0;         if (GetParent(hwnd) == IntPtr.Zero)         {             GetWindowThreadProcessId(hwnd, ref uiPid);             if (uiPid == lParam)    // 找到进程对应的主窗口句柄             {                 processWnd[uiPid] = hwnd;   // 把句柄缓存起来                 SetLastError(0);    // 设置无错误                 return false;   // 返回 false 以终止枚举窗口             }         }         return true;     } }