写在前面

在做录屏或截屏操作时，需要获取当前正在运行中的桌面程序句柄，在网上查找资源的的时候，发现了一个工具类还不错，这边做个验证记录。

参考代码

    public class WindowApi
    {
        //寻找目标进程窗口       
        [DllImport("USER32.DLL")]
        public static extern IntPtr FindWindow(string lpClassName, string lpWindowName);
        //设置进程窗口到最前       
        [DllImport("USER32.DLL")]
        public static extern bool SetForegroundWindow(IntPtr hWnd);

        #region GetWindowCapture的dll引用
        [DllImport("user32.dll")]
        private static extern IntPtr GetWindowRect(IntPtr hWnd, ref Rectangle rect);

        [DllImport("gdi32.dll")]
        private static extern IntPtr CreateCompatibleDC(
         IntPtr hdc // handle to DC
         );
        [DllImport("gdi32.dll")]
        private static extern IntPtr CreateCompatibleBitmap(
         IntPtr hdc,         // handle to DC
         int nWidth,      // width of bitmap, in pixels
         int nHeight      // height of bitmap, in pixels
         );
        [DllImport("gdi32.dll")]
        private static extern IntPtr SelectObject(
         IntPtr hdc,           // handle to DC
         IntPtr hgdiobj    // handle to object
         );
        [DllImport("gdi32.dll")]
        private static extern int DeleteDC(
         IntPtr hdc           // handle to DC
         );
        [DllImport("user32.dll")]
        private static extern bool PrintWindow(
         IntPtr hwnd,                // Window to copy,Handle to the window that will be copied.
         IntPtr hdcBlt,              // HDC to print into,Handle to the device context.
         UInt32 nFlags               // Optional flags,Specifies the drawing options. It can be one of the following values.
         );
        [DllImport("user32.dll")]
        private static extern IntPtr GetWindowDC(
         IntPtr hwnd
         );
        #endregion
        /// <summary>
        /// 根据句柄获取截图
        /// </summary>
        /// <param name="hWnd"></param>
        /// <returns></returns>
        public static Bitmap GetWindowCapture(IntPtr hWnd)
        {
            IntPtr hscrdc = GetWindowDC(hWnd);
            Rectangle windowRect = new Rectangle();
            GetWindowRect(hWnd, ref windowRect);
            int width = Math.Abs(windowRect.X - windowRect.Width);
            int height = Math.Abs(windowRect.Y - windowRect.Height);
            IntPtr hbitmap = CreateCompatibleBitmap(hscrdc, width, height);
            IntPtr hmemdc = CreateCompatibleDC(hscrdc);
            SelectObject(hmemdc, hbitmap);
            PrintWindow(hWnd, hmemdc, 0);
            Bitmap bmp = Image.FromHbitmap(hbitmap);
            DeleteDC(hscrdc);//删除用过的对象
            DeleteDC(hmemdc);//删除用过的对象
            return bmp;
        }
        /// <summary>
        /// 根据句柄获取截图路径
        /// </summary>
        /// <param name="hWnd"></param>
        /// <returns></returns>
        public static string GetCapturePath(IntPtr hWnd)
        {
            string path = string.Empty;
            string dicPath = AppDomain.CurrentDomain.BaseDirectory + "Intercept";
            if (!Directory.Exists(dicPath))
            {
                Directory.CreateDirectory(dicPath);
            }
            using (Bitmap bitmap = GetWindowCapture(hWnd))
            {
                path = dicPath + "\\" + Guid.NewGuid().ToString().Replace("-", "") + ".png";
                bitmap.Save(path);
            }
            return path;
        }


        private delegate bool WNDENUMPROC(IntPtr hWnd, int lParam);

        //用来遍历所有窗口 
        [DllImport("user32.dll")]
        private static extern bool EnumWindows(WNDENUMPROC lpEnumFunc, int lParam);

        //获取窗口Text 
        [DllImport("user32.dll")]
        private static extern int GetWindowTextW(IntPtr hWnd, [MarshalAs(UnmanagedType.LPWStr)] StringBuilder lpString, int nMaxCount);

        //获取窗口类名 
        [DllImport("user32.dll")]
        private static extern int GetClassNameW(IntPtr hWnd, [MarshalAs(UnmanagedType.LPWStr)] StringBuilder lpString, int nMaxCount);

        //自定义一个结构，用来保存句柄信息
        public struct WindowInfo
        {
            public IntPtr hWnd;
            public string szWindowName;
            public string szClassName;
        }

        public static WindowInfo[] GetAllDesktopWindows()
        {
            //用来保存窗口对象 列表
            List<WindowInfo> wndList = new List<WindowInfo>();

            //enum all desktop windows 
            EnumWindows(delegate (IntPtr hWnd, int lParam)
            {
                WindowInfo wnd = new WindowInfo();
                StringBuilder sb = new StringBuilder(256);

                //get hwnd 
                wnd.hWnd = hWnd;

                //get window name  
                GetWindowTextW(hWnd, sb, sb.Capacity);
                wnd.szWindowName = sb.ToString();

                //get window class 
                GetClassNameW(hWnd, sb, sb.Capacity);
                wnd.szClassName = sb.ToString();

                //add it into list 
                wndList.Add(wnd);
                return true;
            }, 0);

            return wndList.ToArray();
        }

        [DllImport("kernel32.dll", EntryPoint = "SetProcessWorkingSetSize")]
        public static extern int SetProcessWorkingSetSize(IntPtr process, int minSize, int maxSize);

        /// <summary>
        /// 释放内存
        /// </summary>
        public async static Task ClearMemory()
        {
            //获得当前工作进程
            Process proc = Process.GetCurrentProcess();
            long usedMemory = proc.PrivateMemorySize64;
            if (usedMemory > 1024 * 1024 * 10)
            {
                GC.Collect();
                GC.WaitForPendingFinalizers();
                if (Environment.OSVersion.Platform == PlatformID.Win32NT)
                {
                    SetProcessWorkingSetSize(Process.GetCurrentProcess().Handle, -1, -1);
                }
                await Task.Delay(10);
            }
        }
    }

调用结果

调用示意：

var programList = WindowApi.GetAllDesktopWindows().Where(x => !string.IsNullOrEmpty(x.szWindowName)).ToList();
listBoxWindows.DataSource = programList.Select(x => x.szWindowName).ToList();