c# - Create child processes in parallel and wait till all child processes terminate

In one of my projects I had to invoke an external exe in parallel for carrying out simple command to execute a script in Hadoop. The parent process had to wait till all the child processes would complete execution on HDFS and then would carry on other steps.

Below is a simple example to achieve the same.In this example I have created an exe to write to a file i.e. SimpleWrite.exe. I call this exe in parallel (5 instances in parallel) and pass in an argument.The parent process that calls this exe waits till all instances of SimpleWrite completes and then continues its steps.


Program to call external exes in Parallel

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ProcessWait
{
    class Program
    {
        static void Main(string[] args)
        {
            try
            {

                Console.WriteLine("Parent process started executing...");
                Console.WriteLine("Parent process is starting child processes...");
                Parallel.For(0, 5, iIndex =>
                {
                    Console.WriteLine("Child process {0} started",iIndex);
                    NewProcess(iIndex);
                });
                Console.WriteLine("All child processes completed.Waiting for user to press the enter key !!!");
                Console.Read();
                Console.WriteLine("Parent process to continue execution.");
                for (int iIndex = 0; iIndex < 10000; iIndex++)
                {
                    Console.WriteLine(iIndex.ToString());
                }
                Console.WriteLine("Parent process completed execution.");
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
            }
            Console.Read();
        }

        private static void NewProcess(int iIndex)
        {
            Process oRunIndex = new Process();
            oRunIndex.StartInfo.FileName = "SimpleWrite.exe";
            oRunIndex.StartInfo.WorkingDirectory = @"c:\Data\";
            oRunIndex.StartInfo.CreateNoWindow = true;
            oRunIndex.StartInfo.Arguments = string.Format("{0}",iIndex);
            
            oRunIndex.Start();
            oRunIndex.WaitForExit();
        }
    }

}

SimpleWrite.exe code

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;

namespace SimpleWrite
{
    class Program
    {
        static void Main(string[] args)
        {
            try
            {
                string sIndex = args[0];
                using(StreamWriter oWriter = new StreamWriter(@"c:\Data\" + sIndex +".txt"))
                {
                    for (int iIndex = 0; iIndex < 100000; iIndex++)
                    {
                        Console.WriteLine(iIndex.ToString());
                        oWriter.WriteLine(iIndex.ToString());
                    }
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
                Console.Read();
            }
        }
    }
}


Output