1. 判斷窗口是否存在

 1     private bool IsWindowExist(IntPtr handle)
 2     {
 3         return (!(GetWindow(new HandleRef(this, handle), 4) != IntPtr.Zero) && IsWindowVisible(new HandleRef(this, handle)));
 4     }
 5 
 6     [DllImport("user32.dll", CharSet = CharSet.Auto, ExactSpelling = true
 
)]
 7     public static extern IntPtr GetWindow(HandleRef hWnd, int uCmd);
 8 
 9     [DllImport("user32.dll", CharSet = CharSet.Auto)]
10     public static extern bool IsWindowVisible(HandleRef hWnd);

2. 獲取窗口句柄

 1     /// <summary>
 2     /// 獲取應用程序窗口句柄
 3     /// </summary>
 4     /// <param name="processId"></param>
 

 5     /// <returns></returns>
 6     private IntPtr GetWindowHandle(int processId)
 7     {
 8         var windowHandle = IntPtr.Zero;
 9         EnumThreadWindowsCallback windowsCallback = new EnumThreadWindowsCallback(FindMainWindow);
10         EnumWindows(windowsCallback, IntPtr.Zero);
 
11         //保持循環
12         GC.KeepAlive(windowsCallback);
13 
14         bool FindMainWindow(IntPtr handle, IntPtr extraParameter)
15         {
16             int num;
17             GetWindowThreadProcessId(new HandleRef(this, handle), out num);
18             if (num == processId && IsWindowExist(handle))
19             {
20                 windowHandle = handle;
21                 return true;
22             }
23             return false;
24         }
25 
26         return windowHandle;
27     }
28     public delegate bool EnumThreadWindowsCallback(IntPtr hWnd, IntPtr lParam);
29 
30     [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
31     public static extern bool EnumWindows(EnumThreadWindowsCallback callback, IntPtr extraData);
32 
33     [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
34     public static extern int GetWindowThreadProcessId(HandleRef handle, out int processId);

3. 關閉應用窗口

根據進程Id關閉應用窗口：

 1     /// <summary>
 2     /// 關閉程序主窗口
 3     /// </summary>
 4     /// <param name="processId">進程ID</param>
 5     public void CloseWindow(int processId)
 6     {
 7         var mwh = GetWindowHandle(processId);
 8         SendMessage(mwh, MW_CLOSE, 0, 0);
 9     }
10     const int MW_CLOSE = 0x0010;
11 
12     [DllImport("User32.dll", EntryPoint = "SendMessage")]
13     private static extern int SendMessage(IntPtr hWnd, int Msg, int wParam, int lParam);

關閉所有此進程名的窗口：

1         public void CloseAllWindows(string processName)
2         {
3             Process[] processList = Process.GetProcessesByName(processName);
4             foreach (Process process in processList)
5             {
6                 CloseMainWindow(process.Id);
7             }
8         }

當然，直接殺進程，是最快的方法：

 1     /// <summary>
 2     /// 關閉所有進程
 3     /// </summary>
 4     /// <param name="processName"></param>
 5     /// <returns></returns>
 6     public static bool CloseAllProcesses(string processName)
 7     {
 8         try
 9         {
10             Process[] psEaiNotes = Process.GetProcessesByName(processName);
11             foreach (Process psEaiNote in psEaiNotes)
12             {
13                 psEaiNote.Kill();
14             }
15         }
16         catch
17         {
18             return false;
19         }
20 
21         return true;
22     }

4. 重啟程序

 1     string appFileName = currentClientProcess.MainModule.FileName;
 2 
 3     Process newClient = new Process();
 4     newClient.StartInfo.FileName = appFileName;
 5     // 設置要啟動的進程的初始目錄
 6     newClient.StartInfo.WorkingDirectory = System.Windows.Forms.Application.ExecutablePath;
 7     
 8     //啟動程序
 9     currentClientProcess.Kill();
10     newClient.Start();

窗口之間發送/接收消息的處理，請參考《C# 跨進程通信》

C# 通過進程名/進程Id 操作窗口