OBTENIR LE PID PARENT D'UN PROCESSUS

using System;
using System.Runtime.InteropServices;

/// <summary>
/// Gère les processus
/// </summary>
public class ProcessManager
{
    [DllImport("kernel32.dll", SetLastError=true)]
    static extern IntPtr CreateToolhelp32Snapshot(uint dwFlags,
	  uint th32ProcessID);


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


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

    [DllImport("kernel32.dll", SetLastError=true)]
    static extern bool CloseHandle(IntPtr hObject);

    /// <summary>
    /// structure d'information sur un processus
    /// </summary>
    [StructLayout(LayoutKind.Sequential)]
	  internal 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; 
    }; 

    const int TH32CS_SNAPPROCESS = 2;
    const int SIZEOF_PROCESSENTRY32 = 564;
    const int SIZE_OFFSET = 0;
    const int PROCESS_OFFSET = 8;
    const int PARENT_OFFSET = 24;




    /// <summary>
    /// Renvoi le PID du processus parent 
    /// </summary>
    /// <param name="Pid"></param>
    /// <returns></returns>
    public static uint GetParentProcess(uint Pid)
    {
	  //structure d'information sur un processus
	  PROCESSENTRY32 _pe = new PROCESSENTRY32();
	  _pe.dwSize = (uint)Marshal.SizeOf(typeof(PROCESSENTRY32));


	  //Handle pour accèder aux infos des processus
	  IntPtr handleProcess = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS,0);

	  uint PidParent = 0;

	  try
	  {
		//Récupère la structure de processus sur le premier Handle
		bool rv = Process32First(handleProcess,ref _pe);

		if(!rv)
		     throw new Exception("Ne peut pas énumérer les processus");

		//tant qu'il y a des processus à éumérer
		while(rv)
		{
		     uint pid = _pe.th32ProcessID;
		     uint parent = _pe.th32ParentProcessID; 

		     if( pid == Pid ) //si c'est le process en cours
		     {
			   //on va renvoyer le process parent
			   PidParent = parent;
			   break; //sorti du while, on arrête d'énumérer les processus
		     }

		     //Récupère la structure de processus sur le handle suivant
		     rv = Process32Next(handleProcess, ref _pe);
		}      
	  }
	  finally
	  {
		CloseHandle(handleProcess);
	  }

	  return PidParent;
    }
}

/***********************************************************************************
***********************************************************************************
***********************************************************************************
***********************************************************************************/

//Utilisation
uint current_pid = (uint)Process.GetCurrentProcess().Id;
uint parent_pid = ProcessManager.GetParentProcess(current_pid);
Process parent_process = Process.GetProcessById((int)parent_pid);
string strParentFilePath = parent_process.MainModule.ModuleName;