public void MainMethod()
    {
        foreach (var x in _ListUser)
            tasks.Add(Task.Run(() => Update1Record(x)));
        Task.WhenAll(tasks).Wait();
    }
    public string Update1Record(UserViewModel objUser)
    {
        using (var VibrantDbContext = new VIBRANT())
        using (var AuditDb = new VibrantAuditEntities())
        using (var VibrantTransaction = VibrantDbContext.Database.BeginTransaction(System.Data.IsolationLevel.ReadCommitted))
        using (var AuditTransaction = AuditDb.Database.BeginTransaction(System.Data.IsolationLevel.ReadCommitted))
        {
            try
            {
                VibrantDbContext.Database.Initialize(force: false);
                AuditDb.Database.Initialize(force: false);
                VibrantDbContext.Configuration.AutoDetectChangesEnabled = false;
                var _ObjUserItem = FillupDateTimeValues(objUser);
                ImportToDB(_ObjUserItem, 0, VibrantDbContext, AuditDb);
                BuildImportLog(objUser, VibrantDbContext, AuditDb);
                VibrantDbContext.SaveChanges();
                AuditDb.SaveChanges();
                VibrantTransaction.Commit();
                AuditTransaction.Commit();
            }
            catch (Exception ex)
            {
                VibrantTransaction.Rollback();
                AuditTransaction.Rollback();
                throw;
            }
        }
        return "S";
    }