public void TestMethod1() { Synchronized synchro = new Synchronized(); Task.Run ( () => { for (int i = 0; i < 1000; i++) { synchro.Customers.Add(new Customer()); } } ); for (int i = 0; i < 1000; i++) { Task.Run(() => synchro.ThreadSynchronization()); } synchro.ThreadSynchronization(); }