Getting Parent Process ID from Child without passing any arguments

In C#, Parent runs ProcessChild through System.Diagonastics.Process and ProcessChild has following codes to find its Parent process Id without use of any arguments.

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;
using System.Collections;
using System.Diagnostics;
namespace ProcessChild
class Program
static void Main(string[] args)

private static Process GetParentProcess()
int iParentPid = 0;
int iCurrentPid = Process.GetCurrentProcess().Id;

IntPtr oHnd = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);

if (oHnd == IntPtr.Zero)
return null;


oProcInfo.dwSize =

if (Process32First(oHnd, ref oProcInfo) == false)
return null;

if (iCurrentPid == oProcInfo.th32ProcessID)
iParentPid = (int)oProcInfo.th32ParentProcessID;
while (iParentPid == 0 && Process32Next(oHnd, ref oProcInfo));

if (iParentPid > 0)
return Process.GetProcessById(iParentPid);
return null;

static uint TH32CS_SNAPPROCESS = 2;

public struct PROCESSENTRY32
public uint dwSize;
public uint cntUsage;
public uint th32ProcessID;
public IntPtr th32DefaultHeapID;
public uint th32ModuleID;
public uint cntThreads;
public uint th32ParentProcessID;
public int pcPriClassBase;
public uint dwFlags;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 260)]
public string szExeFile;

[DllImport("kernel32.dll", SetLastError = true)]
static extern IntPtr CreateToolhelp32Snapshot(uint dwFlags, uint th32ProcessID);

static extern bool Process32First(IntPtr hSnapshot, ref PROCESSENTRY32 lppe);

static extern bool Process32Next(IntPtr hSnapshot, ref PROCESSENTRY32 lppe);


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