隨筆6 - 獲取當前程序的句柄

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

        public 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);
    }