How terminate child processes when parent process terminated in C#

Task: Auto kill all child processes if parent process terminate. Parent procees can be terminated not only in correct way, but also by killing in ProcessExplorer, for example. How can I do it?

Similar question in С topic advice to use Job objects. How to use it in C# without exporting external DLL?

I tried to use Job Objects. But this code doesn't work properly:

  var job = PInvoke.CreateJobObject(null, null);
  var jobli = new PInvoke.JOBOBJECT_BASIC_LIMIT_INFORMATION();

  jobli.LimitFlags = PInvoke.LimitFlags.JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE
                   | PInvoke.LimitFlags.JOB_OBJECT_LIMIT_PRIORITY_CLASS
                   | PInvoke.LimitFlags.JOB_OBJECT_LIMIT_JOB_TIME
                   | PInvoke.LimitFlags.JOB_OBJECT_LIMIT_DIE_ON_UNHANDLED_EXCEPTION
                   | PInvoke.LimitFlags.JOB_OBJECT_LIMIT_JOB_MEMORY;

  var res = PInvoke.SetInformationJobObject(job, PInvoke.JOBOBJECTINFOCLASS.JobObjectBasicLimitInformation, jobli, 48);

  if (!res)
  {
    int b = PInvoke.GetLastError();
    Console.WriteLine("Error " + b);
  }

  var Prc = Process.Start(...);

  PInvoke.AssignProcessToJobObject(job, Prc.Handle);

PInvoke.SetInformationJobObject returns with error. GetLastError returns error 24. However, PInvoke.AssignProcessToJobObject works and child process added to Job Queue (I can see it in ProcessExplorer). But, because PInvoke.SetInformationJobObject don't work - spawned process stay alive when I kill parent one.

What do I have incorrect in this code?