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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