test.cs

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

class C {
	static void Main ()
	{
		Console.WriteLine ($"PID: {Process.GetCurrentProcess ().Id}");
		for (int i = 0; i < 10000; i++) {
			Console.WriteLine ($"Iteration #{i}");
			RunProcess ();
		}
	}

	static void RunProcess ()
	{
			var info = new ProcessStartInfo ("echo", "abc");
			info.UseShellExecute = false;
			info.RedirectStandardInput = false;
			info.RedirectStandardOutput = true;
			info.RedirectStandardError = true;
			var stdout_completed = new System.Threading.ManualResetEvent (false);
			var stderr_completed = new System.Threading.ManualResetEvent (false);
			var output = new StringBuilder ();

			using (var p = Process.Start (info)) {

				p.OutputDataReceived += (s, e) => {
					if (e.Data != null) {
						lock (output)
							output.AppendLine (e.Data);
					} else {
						stdout_completed.Set ();
					}
				};

				p.ErrorDataReceived += (s, e) => {
					if (e.Data != null) {
						lock (output)
							output.AppendLine (e.Data);
					} else {
						stderr_completed.Set ();
					}
				};

				p.BeginOutputReadLine ();
				p.BeginErrorReadLine ();

				p.WaitForExit ();

				stderr_completed.WaitOne (TimeSpan.FromSeconds (1));
				stdout_completed.WaitOne (TimeSpan.FromSeconds (1));

				Console.Error.WriteLine ($"Process exited with code {p.ExitCode}");
				Console.WriteLine (output.ToString ());

				p.StandardOutput.Close ();
				// FIX:
				// GC.Collect ();
			}

	}
}