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C#如何实现子进程跟随主进程关闭

作者：CodeOfCC

多进程开发经常会遇到主进程关闭,子进程需要跟随主进程一同关闭,比如调ffmpeg命令行实现的录屏程序等,下面我们就来看看C#是如何实现子进程跟随主进程关闭的吧

前言

多进程开发经常会遇到主进程关闭，子进程需要跟随主进程一同关闭。比如调ffmpeg命令行实现的录屏程序，录屏程序关闭，ffmpeg进程也需要退出。我们通常在程序关闭时调用Process.Kill()杀掉fmpeg进程即可。但是如果是强制或异常关闭录屏程序，ffmpeg将会变成僵尸进程残留在系统中。本文将提供一种解决此类问题的方法。

一、如何实现

1、创建作业对象

（1）、创建对象

handle = CreateJobObject(IntPtr.Zero, null);

（2）、设置销毁作业时，关闭拥有的进程

var info = new JOBOBJECT_BASIC_LIMIT_INFORMATION
{
    LimitFlags = 0x2000
};
var extendedInfo = new JOBOBJECT_EXTENDED_LIMIT_INFORMATION
{
    BasicLimitInformation = info
};

int length = Marshal.SizeOf(typeof(JOBOBJECT_EXTENDED_LIMIT_INFORMATION));
IntPtr extendedInfoPtr = Marshal.AllocHGlobal(length);
Marshal.StructureToPtr(extendedInfo, extendedInfoPtr, false);

if (!SetInformationJobObject(handle, JobObjectInfoType.ExtendedLimitInformation, extendedInfoPtr, (uint)length))
    throw new Exception(string.Format("Unable to set information.  Error: {0}", Marshal.GetLastWin32Error()));

2、子进程加入作业对象

AssignProcessToJobObject(handle, processHandle);

3、销毁作业对象

（1）、手动销毁

CloseHandle(handle);

（2）、所在进程结束自动销毁

二、完整代码

using System.Diagnostics;
using System.Runtime.InteropServices;
namespace JobManagement
{
    #region Helper classes
    /// <summary>
    ///  作业对象，主要用于子进程管理。
    ///  目前版本是只支持作业销毁拥有的子进程退出
    ///  通常可以定义一个全局静态变量使用
    /// </summary>
    public class Job : IDisposable
    {
        [DllImport("kernel32.dll", CharSet = CharSet.Unicode)]
        static extern IntPtr CreateJobObject(IntPtr a, string lpName);
        [DllImport("kernel32.dll")]
        static extern bool SetInformationJobObject(IntPtr hJob, JobObjectInfoType infoType, IntPtr lpJobObjectInfo, UInt32 cbJobObjectInfoLength);
        [DllImport("kernel32.dll", SetLastError = true)]
        static extern bool AssignProcessToJobObject(IntPtr job, IntPtr process);
        [DllImport("kernel32.dll", SetLastError = true)]
        [return: MarshalAs(UnmanagedType.Bool)]
        static extern bool CloseHandle(IntPtr hObject);
        private IntPtr handle;
        private bool disposed;
        public Job()
        {
            handle = CreateJobObject(IntPtr.Zero, null);
            var info = new JOBOBJECT_BASIC_LIMIT_INFORMATION
            {
                LimitFlags = 0x2000
            };
            var extendedInfo = new JOBOBJECT_EXTENDED_LIMIT_INFORMATION
            {
                BasicLimitInformation = info
            };
            int length = Marshal.SizeOf(typeof(JOBOBJECT_EXTENDED_LIMIT_INFORMATION));
            IntPtr extendedInfoPtr = Marshal.AllocHGlobal(length);
            Marshal.StructureToPtr(extendedInfo, extendedInfoPtr, false);
            if (!SetInformationJobObject(handle, JobObjectInfoType.ExtendedLimitInformation, extendedInfoPtr, (uint)length))
                throw new Exception(string.Format("Unable to set information.  Error: {0}", Marshal.GetLastWin32Error()));
        }
        /// <summary>
        /// 进程加入到作业对象中
        /// </summary>
        /// <param name="processHandle">进程句柄</param>
        /// <returns></returns>
        public bool AddProcess(IntPtr processHandle)
        {
            return AssignProcessToJobObject(handle, processHandle);
        }

        /// <summary>
        /// 进程加入到作业对象中
        /// </summary>
        /// <param name="processId">进程Id</param>
        /// <returns></returns>
        public bool AddProcess(int processId)
        {
            return AddProcess(Process.GetProcessById(processId).Handle);
        }
        /// <summary>
        /// 销毁作业对象，手动调用则其拥有的所有进程都会退出
        /// </summary>
        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }
        /// <summary>
        /// 销毁作业对象，手动调用则其拥有的所有进程都会退出
        /// </summary>
        public void Close()
        {
            CloseHandle(handle);
            handle = IntPtr.Zero;
        }
        private void Dispose(bool disposing)
        {
            if (disposed)
                return;
            if (disposing) { }
            Close();
            disposed = true;
        }
    }

    [StructLayout(LayoutKind.Sequential)]
    struct IO_COUNTERS
    {
        public UInt64 ReadOperationCount;
        public UInt64 WriteOperationCount;
        public UInt64 OtherOperationCount;
        public UInt64 ReadTransferCount;
        public UInt64 WriteTransferCount;
        public UInt64 OtherTransferCount;
    }

    [StructLayout(LayoutKind.Sequential)]
    struct JOBOBJECT_BASIC_LIMIT_INFORMATION
    {
        public Int64 PerProcessUserTimeLimit;
        public Int64 PerJobUserTimeLimit;
        public UInt32 LimitFlags;
        public UIntPtr MinimumWorkingSetSize;
        public UIntPtr MaximumWorkingSetSize;
        public UInt32 ActiveProcessLimit;
        public UIntPtr Affinity;
        public UInt32 PriorityClass;
        public UInt32 SchedulingClass;
    }

    [StructLayout(LayoutKind.Sequential)]
    public struct SECURITY_ATTRIBUTES
    {
        public UInt32 nLength;
        public IntPtr lpSecurityDescriptor;
        public Int32 bInheritHandle;
    }

    [StructLayout(LayoutKind.Sequential)]
    struct JOBOBJECT_EXTENDED_LIMIT_INFORMATION
    {
        public JOBOBJECT_BASIC_LIMIT_INFORMATION BasicLimitInformation;
        public IO_COUNTERS IoInfo;
        public UIntPtr ProcessMemoryLimit;
        public UIntPtr JobMemoryLimit;
        public UIntPtr PeakProcessMemoryUsed;
        public UIntPtr PeakJobMemoryUsed;
    }

    public enum JobObjectInfoType
    {
        AssociateCompletionPortInformation = 7,
        BasicLimitInformation = 2,
        BasicUIRestrictions = 4,
        EndOfJobTimeInformation = 6,
        ExtendedLimitInformation = 9,
        SecurityLimitInformation = 5,
        GroupInformation = 11
    }
    #endregion
}

三、使用示例

1、正常退出自动结束子进程

.net8.0

using System.Diagnostics;
using JobManagement;
//创建作业对象
Job _job = new Job();
//打开记事本程序
var ps = new Process();
ps.StartInfo.FileName = "notepad.exe";
ps.Start();
//记事本程序进程加入到作业对象
_job.AddProcess(ps.Handle);
//等待3秒后退出程序，记事本程序会自动关闭
Thread.Sleep(3000);

效果预览

2、异常退出自动结束子进程

.net8.0

using System.Diagnostics;
using JobManagement;
//创建作业对象
Job _job = new Job();
//打开记事本程序
var ps = new Process();
ps.StartInfo.FileName = "notepad.exe";
ps.Start();
//记事本程序进程加入到作业对象
_job.AddProcess(ps.Handle);
while(true)Thread.Sleep(3000);

效果预览

总结

本文讲述的内容是windows多进程开发中比较重要的技术，因为大部分场景主进程退出后子进程应该跟随退出，正常流程中通过代码可以在退出时关闭所有子进程，但是异常崩溃时则不行，会出现遗留子进程。而本文的方法就很好的解决的这个问题，而且也不需要编写任何关闭子进程的相关代码，方便且省心。

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