How to get parent process in .NET in managed way

Question

I was looking a lot for method to get parent process in .NET, but found only P/Invoke way.

Answer 1

If you've ever digged the BCL, you shall find that the ways to find parent process are deliberately avoided, take this for example:

https://referencesource.microsoft.com/#System/services/monitoring/system/diagnosticts/ProcessManager.cs,327

As you can see in the source code, it contains comprehensive structures and imported native methods which are absolutely sufficient to get the job done. However, even if you access them via reflection(this is possible), you would not find a method for doing it directly. I can't answer why, yet this phenomenon causes questions like yours are asked for somewhat repeatedly; for example:

How can I get the PID of the parent process of my application

For there is no answer along with some code using CreateToolhelp32Snapshot in this thread, I'd add it -- part of the structure definitions and names I steal from the MS' reference source :)

• Code

  using System.Diagnostics;
  using System.Runtime.InteropServices;
  using System.Collections.Generic;
  using System.Linq;
  using System;
  

  ---

  public static class Toolhelp32 {
      public const uint Inherit = 0x80000000;
      public const uint SnapModule32 = 0x00000010;
      public const uint SnapAll = SnapHeapList|SnapModule|SnapProcess|SnapThread;
      public const uint SnapHeapList = 0x00000001;
      public const uint SnapProcess = 0x00000002;
      public const uint SnapThread = 0x00000004;
      public const uint SnapModule = 0x00000008;
  
      [DllImport("kernel32.dll")]
      static extern bool CloseHandle(IntPtr handle);
      [DllImport("kernel32.dll")]
      static extern IntPtr CreateToolhelp32Snapshot(uint flags, int processId);
  
      public static IEnumerable<T> TakeSnapshot<T>(uint flags, int id) where T : IEntry, new() {
          using(var snap = new Snapshot(flags, id))
              for(IEntry entry = new T { }; entry.TryMoveNext(snap, out entry);)
                  yield return (T)entry;
      }
  
      public interface IEntry {
          bool TryMoveNext(Toolhelp32.Snapshot snap, out IEntry entry);
      }
  
      public struct Snapshot:IDisposable {
          void IDisposable.Dispose() {
              Toolhelp32.CloseHandle(m_handle);
          }
          public Snapshot(uint flags, int processId) {
              m_handle=Toolhelp32.CreateToolhelp32Snapshot(flags, processId);
          }
          IntPtr m_handle;
      }
  }
  

  ---

  [StructLayout(LayoutKind.Sequential)]
  public struct WinProcessEntry:Toolhelp32.IEntry {
      [DllImport("kernel32.dll")]
      public static extern bool Process32Next(Toolhelp32.Snapshot snap, ref WinProcessEntry entry);
  
      public bool TryMoveNext(Toolhelp32.Snapshot snap, out Toolhelp32.IEntry entry) {
          var x = new WinProcessEntry { dwSize=Marshal.SizeOf(typeof(WinProcessEntry)) };
          var b = Process32Next(snap, ref x);
          entry=x;
          return b;
      }
  
      public int dwSize;
      public int cntUsage;
      public int th32ProcessID;
      public IntPtr th32DefaultHeapID;
      public int th32ModuleID;
      public int cntThreads;
      public int th32ParentProcessID;
      public int pcPriClassBase;
      public int dwFlags;
      [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 260)]
      public String fileName;
      //byte fileName[260];
      //public const int sizeofFileName = 260;
  }
  

  ---

  public static class Extensions {
      public static Process Parent(this Process p) {
          var entries = Toolhelp32.TakeSnapshot<WinProcessEntry>(Toolhelp32.SnapAll, 0);
          var parentid = entries.First(x => x.th32ProcessID==p.Id).th32ParentProcessID;
          return Process.GetProcessById(parentid);
      }
  }
  

And we can use it like:

• Test

  public class TestClass {
      public static void TestMethod() {
          var p = Process.GetCurrentProcess().Parent();
          Console.WriteLine("{0}", p.Id);
      }
  }
  

---

For alternative ending ..

According to the documentation, there are a pair of iteration methods per type of the entries such as Process32First and Process32Next are for the iteration of processes; but I found the `xxxxFirst' methods are unnecessary, and then I thought why not put the iteration method with its corresponding entry type? It'd be easier to implement and be understood(I guess so ..).

Just as Toolhelp32 suffixed with help, I think a static helper class is proper, so that we can have the clear qualified names such as Toolhelp32.Snapshot or Toolhelp32.IEntry though it'd be irrelevant here ..

Once the parent process is obtained, if you further want to get some detailed infos, you can extend with this easily, for example, iterate on its modules, then add:

• Code - WinModuleEntry

  [StructLayout(LayoutKind.Sequential)]
  public struct WinModuleEntry:Toolhelp32.IEntry { // MODULEENTRY32
      [DllImport("kernel32.dll")]
      public static extern bool Module32Next(Toolhelp32.Snapshot snap, ref WinModuleEntry entry);
  
      public bool TryMoveNext(Toolhelp32.Snapshot snap, out Toolhelp32.IEntry entry) {
          var x = new WinModuleEntry { dwSize=Marshal.SizeOf(typeof(WinModuleEntry)) };
          var b = Module32Next(snap, ref x);
          entry=x;
          return b;
      }
  
      public int dwSize;
      public int th32ModuleID;
      public int th32ProcessID;
      public int GlblcntUsage;
      public int ProccntUsage;
      public IntPtr modBaseAddr;
      public int modBaseSize;
      public IntPtr hModule;
      //byte moduleName[256];
      [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 256)]
      public string moduleName;
      [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 260)]
      public string fileName;
      //byte fileName[260];
      //public const int sizeofModuleName = 256;
      //public const int sizeofFileName = 260;
  }
  

  ---

  and some test ..

  public class TestClass {
      public static void TestMethod() {
          var p = Process.GetCurrentProcess().Parent();
          Console.WriteLine("{0}", p.Id);
  
          var formatter = new CustomFormatter { };
          foreach(var x in Toolhelp32.TakeSnapshot<WinModuleEntry>(Toolhelp32.SnapModule, p.Id)) {
              Console.WriteLine(String.Format(formatter, "{0}", x));
          }
      }
  }
  
  public class CustomFormatter:IFormatProvider, ICustomFormatter {
      String ICustomFormatter.Format(String format, object arg, IFormatProvider formatProvider) {
          var type = arg.GetType();
          var fields = type.GetFields();
          var q = fields.Select(x => String.Format("{0}:{1}", x.Name, x.GetValue(arg)));
          return String.Format("{{{0}}}", String.Join(", ", q.ToArray()));
      }
  
      object IFormatProvider.GetFormat(Type formatType) {
          return typeof(ICustomFormatter)!=formatType ? null : this;
      }
  }
  

In case you want a code example ..

• https://github.com/kenkins/ToolHelp32ConsoleApp

Answer 2

If accepting P/Invoke, there's a better way, which is more documented than NtQueryInformationProcess: namely PROCESSENTRY32 (CreateToolhelp32Snapshot, Process32First, Process32Next). It's shown in this post.

Pay attention to the subtle details and note that parent PID is not necessarily the creator PID, in fact these may be completely unrelated, as pointed out by the community comments at PROCESSENTRY32.

Answer 3

Here's my try at a managed solution.

It polls the performance counters for all processes and returns a dictionary of child PID to parent PID. Then you can check the dictionary with your current PID to see your parent, grandparent, etc.

It is overkill in how much info it gets, for sure. Feel free to optimize.

using System;
using System.Collections.Generic;
using System.Diagnostics;

namespace PidExamples
{
    class ParentPid
    {
        static void Main(string[] args)
        {
            var childPidToParentPid = GetAllProcessParentPids();
            int currentProcessId = Process.GetCurrentProcess().Id;

            Console.WriteLine("Current Process ID: " + currentProcessId);
            Console.WriteLine("Parent Process ID: " + childPidToParentPid[currentProcessId]);
        }

        public static Dictionary<int, int> GetAllProcessParentPids()
        {
            var childPidToParentPid = new Dictionary<int, int>();

            var processCounters = new SortedDictionary<string, PerformanceCounter[]>();
            var category = new PerformanceCounterCategory("Process");

            // As the base system always has more than one process running, 
            // don't special case a single instance return.
            var instanceNames = category.GetInstanceNames();
            foreach(string t in instanceNames)
            {
                try
                {
                    processCounters[t] = category.GetCounters(t);
                }
                catch (InvalidOperationException)
                {
                    // Transient processes may no longer exist between 
                    // GetInstanceNames and when the counters are queried.
                }
            }

            foreach (var kvp in processCounters)
            {
                int childPid = -1;
                int parentPid = -1;

                foreach (var counter in kvp.Value)
                {
                    if ("ID Process".CompareTo(counter.CounterName) == 0)
                    {
                        childPid = (int)(counter.NextValue());
                    }
                    else if ("Creating Process ID".CompareTo(counter.CounterName) == 0)
                    {
                        parentPid = (int)(counter.NextValue());
                    }
                }

                if (childPid != -1 && parentPid != -1)
                {
                    childPidToParentPid[childPid] = parentPid;
                }
            }

            return childPidToParentPid;
        }
    }
}    

In other news, I learned how many performance counters there were on my machine: 13401. Holy cow.

Answer 4

This way:

public static Process GetParent(this Process process)
{
  try
  {
    using (var query = new ManagementObjectSearcher(
      "SELECT * " +
      "FROM Win32_Process " +
      "WHERE ProcessId=" + process.Id))
    {
      return query
        .Get()
        .OfType<ManagementObject>()
        .Select(p => Process.GetProcessById((int)(uint)p["ParentProcessId"]))
        .FirstOrDefault();
    }
  }
  catch
  {
    return null;
  }
}

Answer 5

This code provides a nice interface for finding the Parent process object and takes into account the possibility of multiple processes with the same name:

Usage:

Console.WriteLine("ParentPid: " + Process.GetProcessById(6972).Parent().Id);

Code:

public static class ProcessExtensions {
    private static string FindIndexedProcessName(int pid) {
        var processName = Process.GetProcessById(pid).ProcessName;
        var processesByName = Process.GetProcessesByName(processName);
        string processIndexdName = null;

        for (var index = 0; index < processesByName.Length; index++) {
            processIndexdName = index == 0 ? processName : processName + "#" + index;
            var processId = new PerformanceCounter("Process", "ID Process", processIndexdName);
            if ((int) processId.NextValue() == pid) {
                return processIndexdName;
            }
        }

        return processIndexdName;
    }

    private static Process FindPidFromIndexedProcessName(string indexedProcessName) {
        var parentId = new PerformanceCounter("Process", "Creating Process ID", indexedProcessName);
        return Process.GetProcessById((int) parentId.NextValue());
    }

    public static Process Parent(this Process process) {
        return FindPidFromIndexedProcessName(FindIndexedProcessName(process.Id));
    }
}

Answer 6

Here is a solution. It uses p/invoke, but seems to work well, 32 or 64 cpu:

    /// <summary>
    /// A utility class to determine a process parent.
    /// </summary>
    [StructLayout(LayoutKind.Sequential)]
    public struct ParentProcessUtilities
    {
        // These members must match PROCESS_BASIC_INFORMATION
        internal IntPtr Reserved1;
        internal IntPtr PebBaseAddress;
        internal IntPtr Reserved2_0;
        internal IntPtr Reserved2_1;
        internal IntPtr UniqueProcessId;
        internal IntPtr InheritedFromUniqueProcessId;

        [DllImport("ntdll.dll")]
        private static extern int NtQueryInformationProcess(IntPtr processHandle, int processInformationClass, ref ParentProcessUtilities processInformation, int processInformationLength, out int returnLength);

        /// <summary>
        /// Gets the parent process of the current process.
        /// </summary>
        /// <returns>An instance of the Process class.</returns>
        public static Process GetParentProcess()
        {
            return GetParentProcess(Process.GetCurrentProcess().Handle);
        }

        /// <summary>
        /// Gets the parent process of specified process.
        /// </summary>
        /// <param name="id">The process id.</param>
        /// <returns>An instance of the Process class.</returns>
        public static Process GetParentProcess(int id)
        {
            Process process = Process.GetProcessById(id);
            return GetParentProcess(process.Handle);
        }

        /// <summary>
        /// Gets the parent process of a specified process.
        /// </summary>
        /// <param name="handle">The process handle.</param>
        /// <returns>An instance of the Process class.</returns>
        public static Process GetParentProcess(IntPtr handle)
        {
            ParentProcessUtilities pbi = new ParentProcessUtilities();
            int returnLength;
            int status = NtQueryInformationProcess(handle, 0, ref pbi, Marshal.SizeOf(pbi), out returnLength);
            if (status != 0)
                throw new Win32Exception(status);

            try
            {
                return Process.GetProcessById(pbi.InheritedFromUniqueProcessId.ToInt32());
            }
            catch (ArgumentException)
            {
                // not found
                return null;
            }
        }
    }