Hey all,

I have a process that is a C# process.  I need to do something different if someone just double-clicks the application than if it is launched by a certain other process.  So I decided to check the parent process.

I couldn’t find a simple C# only method. But I did find a code snippet that works. There were actually lots of posts on that provided the following code snippet or variations thereof, so I consider it to be public domain.  So obviously I didn’t write this part.

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

            IntPtr oHnd = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);

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

            PROCESSENTRY32 oProcInfo = new PROCESSENTRY32();

            oProcInfo.dwSize =
            (uint)System.Runtime.InteropServices.Marshal.SizeOf(typeof(PROCESSENTRY32));

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

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

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

        static uint TH32CS_SNAPPROCESS = 2;

        [StructLayout(LayoutKind.Sequential)]
        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);

        [DllImport("kernel32.dll")]
        static extern bool Process32First(IntPtr hSnapshot, ref PROCESSENTRY32 lppe);

        [DllImport("kernel32.dll")]
        static extern bool Process32Next(IntPtr hSnapshot, ref PROCESSENTRY32 lppe);
    }

I took this code snippet and improved upon it and made myself the following static class. This class more easily exposes:

• Parent Process Id
• Parent Process name
• Parent process executable name
• Full path to parent process executable
• Directory name where the parent process executable resides

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

namespace ParentProcess
{
    public class ParentProcess
    {
        public static String ProcessName
        {
            get { return GetParentProcess().ProcessName; }
        }

        public static int ProcessId
        {
            get { return GetParentProcess().Id; }
        }

        public static String FullPath
        {
            get
            {
                return GetParentProcess().MainModule.FileName;
            }
        }

        public static String FileName
        {
            get
            {
                return System.IO.Path.GetFileName(GetParentProcess().MainModule.FileName);
            }
        }

        public static String DirectoryName
        {
            get
            {
                return System.IO.Path.GetDirectoryName(GetParentProcess().MainModule.FileName);
            }
        }

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

            IntPtr oHnd = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);

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

            PROCESSENTRY32 oProcInfo = new PROCESSENTRY32();

            oProcInfo.dwSize =
            (uint)System.Runtime.InteropServices.Marshal.SizeOf(typeof(PROCESSENTRY32));

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

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

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

        static uint TH32CS_SNAPPROCESS = 2;

        [StructLayout(LayoutKind.Sequential)]
        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);

        [DllImport("kernel32.dll")]
        static extern bool Process32First(IntPtr hSnapshot, ref PROCESSENTRY32 lppe);

        [DllImport("kernel32.dll")]
        static extern bool Process32Next(IntPtr hSnapshot, ref PROCESSENTRY32 lppe);
    }
}

This makes it easier for me to simply include the class above in my code and make simple calls:

String exename = ParentProcess.FileName;
String FullPathToExe = ParentProcess.FullPath;
String DirectoryInWhichExeResides= ParentProcess.DirectoryName;

…and the pid and process name, etc…

I hope this helps you.

References
http://www.facebook.com/note.php?note_id=73447531256
http://www.debugging.com/bug/6657
http://www.eggheadcafe.com/software/aspnet/35541264/how-to-get-the-parent-pro.aspx

No Copyright.