Project Server 2013 Updating Task level Lookup based custom field Using CSOM

Below sample code is to update the task level Lookup table based custom fields for a given project:

         try{

                projectName = "ProjectTest";
                pwapath = "https://Servername/pwa";             
                projContext = new ProjectContext(pwapath);
                projContext.Load(projContext.Projects);
                projContext.ExecuteQuery();
                var proj = projContext.Projects.First(p => p.Name == projectName);
                projContext.ExecuteQuery();             
                var cfInternalName = "Custom_aaf4156c7804e511943500155d569905";    //CustomField field uid without the "-" and small letters
                var draftProj = proj.CheckOut();
                projContext.Load(draftProj.Tasks);
                projContext.ExecuteQuery();
                var tasks = draftProj.Tasks;
                foreach (DraftTask tsk in tasks)
                {
                    string[] Newval = new string[] { "Entry_343982d27604e511943500155d569905" };     //Lookup table value UID without "-"   and small letters                                             
                    tsk[cfInternalName] = Newval;                   

                }              
                draftProj.Publish(true);
                QueueJob qJob = projContext.Projects.Update();
                JobState jobState = projContext.WaitForQueue(qJob, 200);
                Console.ReadKey();

            }
            catch (Exception exc)
            {
                Console.WriteLine(exc.ToString());
            }
            Console.ReadKey();

Happy coding ......Cheers .. Ajith