C#中进程的挂起与恢复

1. 源起：

仍然是模块化编程所引发的需求。产品经理难伺候，女产品经理更甚之~:p

纯属戏谑，技术方案与产品经理无关，芋头莫怪！

VCU10项目重构，要求各功能模块以独立进程方式实现，比如：音视频转换模块，若以独立进程方式实现，如何控制其暂停、继续等功能呢？

线程可以Suspend、Resume，c#内置的Process没有此类方法，咋整？

山穷水尽疑无路，柳暗花明又一村。情到浓时清转薄，此情可待成追忆！

前篇描述了进程间数据传递方法，此篇亦以示例演示其间控制与数据交互方法。

 2、未公开的API函数：NtSuspendProcess、NtResumeProcess

此类函数在MSDN中找不到。

思其原因，概因它们介于Windows API和 内核API之间，威力不容小觑。怕二八耙子程序员滥用而引发事端，因此密藏。

其实还有个NtTerminateProcess，因Process有Kill方法，因此可不用。

但再隐秘的东西，只要有价值，都会被人给翻出来，好酒不怕巷子深么！

好，基于其，设计一个进程管理类，实现模块化编程之进程间控制这个需求。

3、ProcessMgr

直上代码吧，封装一个进程管理单元：

public static class ProcessMgr
 {
  /// <summary>
  /// The process-specific access rights.
  /// </summary>
  [Flags]
  public enum ProcessAccess : uint
  {
   /// <summary>
   /// Required to terminate a process using TerminateProcess.
   /// </summary>
   Terminate = 0x1,
   /// <summary>
   /// Required to create a thread.
   /// </summary>
   CreateThread = 0x2,
   /// <summary>
   /// Undocumented.
   /// </summary>
   SetSessionId = 0x4,
   /// <summary>
   /// Required to perform an operation on the address space of a process (see VirtualProtectEx and WriteProcessMemory).
   /// </summary>
   VmOperation = 0x8,
   /// <summary>
   /// Required to read memory in a process using ReadProcessMemory.
   /// </summary>
   VmRead = 0x10,
   /// <summary>
   /// Required to write to memory in a process using WriteProcessMemory.
   /// </summary>
   VmWrite = 0x20,
   /// <summary>
   /// Required to duplicate a handle using DuplicateHandle.
   /// </summary>
   DupHandle = 0x40,
   /// <summary>
   /// Required to create a process.
   /// </summary>
   CreateProcess = 0x80,
   /// <summary>
   /// Required to set memory limits using SetProcessWorkingSetSize.
   /// </summary>
   SetQuota = 0x100,
   /// <summary>
   /// Required to set certain information about a process, such as its priority class (see SetPriorityClass).
   /// </summary>
   SetInformation = 0x200,
   /// <summary>
   /// Required to retrieve certain information about a process, such as its token, exit code, and priority class (see OpenProcessToken, GetExitCodeProcess, GetPriorityClass, and IsProcessInJob).
   /// </summary>
   QueryInformation = 0x400,
   /// <summary>
   /// Undocumented.
   /// </summary>
   SetPort = 0x800,
   /// <summary>
   /// Required to suspend or resume a process.
   /// </summary>
   SuspendResume = 0x800,
   /// <summary>
   /// Required to retrieve certain information about a process (see QueryFullProcessImageName). A handle that has the PROCESS_QUERY_INFORMATION access right is automatically granted PROCESS_QUERY_LIMITED_INFORMATION.
   /// </summary>
   QueryLimitedInformation = 0x1000,
   /// <summary>
   /// Required to wait for the process to terminate using the wait functions.
   /// </summary>
   Synchronize = 0x100000
  }
  [DllImport("ntdll.dll")]
  private static extern uint NtResumeProcess([In] IntPtr processHandle);
  [DllImport("ntdll.dll")]
  private static extern uint NtSuspendProcess([In] IntPtr processHandle);
  [DllImport("kernel32.dll", SetLastError = true)]
  private static extern IntPtr OpenProcess(
   ProcessAccess desiredAccess,
   bool inheritHandle,
   int processId);
  [DllImport("kernel32.dll", SetLastError = true)]
  [return: MarshalAs(UnmanagedType.Bool)]
  private static extern bool CloseHandle([In] IntPtr handle);
  public static void SuspendProcess(int processId)
  {
   IntPtr hProc = IntPtr.Zero;
   try
   {
    // Gets the handle to the Process
    hProc = OpenProcess(ProcessAccess.SuspendResume, false, processId);
    if (hProc != IntPtr.Zero)
     NtSuspendProcess(hProc);
   }
   finally
   {
    // Don't forget to close handle you created.
    if (hProc != IntPtr.Zero)
     CloseHandle(hProc);
   }
  }
  public static void ResumeProcess(int processId)
  {
   IntPtr hProc = IntPtr.Zero;
   try
   {
    // Gets the handle to the Process
    hProc = OpenProcess(ProcessAccess.SuspendResume, false, processId);
    if (hProc != IntPtr.Zero)
     NtResumeProcess(hProc);
   }
   finally
   {
    // Don't forget to close handle you created.
    if (hProc != IntPtr.Zero)
     CloseHandle(hProc);
   }
  }
 }

4、进程控制

我权且主进程为宿主，它通过Process类调用子进程，得其ID，以此为用。其调用代码为：

 private void RunTestProcess(bool hidden = false)
  {
   string appPath = Path.GetDirectoryName(Application.ExecutablePath);
   string testAppPath = Path.Combine(appPath, "TestApp.exe");
   var pi = new ProcessStartInfo();
   pi.FileName = testAppPath;
   pi.Arguments = this.Handle.ToString();
   pi.WindowStyle = hidden ? ProcessWindowStyle.Hidden : ProcessWindowStyle.Normal;
   this.childProcess = Process.Start(pi);
   txtInfo.Text = string.Format("子进程ID：{0}\r\n子进程名：{1}", childProcess.Id, childProcess.ProcessName);
   ...
  }

控制代码为：    

private void btnWork_Click(object sender, EventArgs e)
  {
   if (this.childProcess == null || this.childProcess.HasExited)
    return;
   if ((int)btnWork.Tag == 0)
   {
    btnWork.Tag = 1;
    btnWork.Text = "恢复";
    ProcessMgr.SuspendProcess(this.childProcess.Id);
   }
   else
   {
    btnWork.Tag = 0;
    btnWork.Text = "挂起";
    ProcessMgr.ResumeProcess(this.childProcess.Id);
   }
  }

子进程以一定时器模拟其工作，向主进程抛进度消息：

 private void timer_Tick(object sender, EventArgs e)
  {
   if (progressBar.Value < progressBar.Maximum)
    progressBar.Value += 1;
   else
    progressBar.Value = 0;
   if (this.hostHandle != IntPtr.Zero)
    SendMessage(this.hostHandle, WM_PROGRESS, 0, progressBar.Value);
  }

代码量就这么的少，简单吧……

5、效果图：

为示例，做了两个图，其一为显示子进程，其二为隐藏子进程。

实际项目调用独立进程模块，是以隐藏方式调用的，以宿主展示其处理进度，如此图：

后记：

扩展思路，一些优秀的开源工具，如youtube_dl、ffmpeg等，都以独立进程方式存在，且可通过CMD管理通信。

以此进程控制原理，可以基于这些开源工具，做出相当不错的GUI工具出来。毕竟相对于强大的命令行，人们还是以简单操作为方便。

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