how threads communicate with eachother?

Question

how threads communicate with eachother? they dont use values of eachother, then what is the way of communication between them?

Answer 1

There are a few ways threads can communicate with each other. This list is not exhaustive, but does include the most used strategies.

• Shared memory, like a variable or some other data structure
• Synchronization primitives, like locks and sempahores
• Events, like ManualResetEvent or AutoResetEvent

Shared memory

public static void Main()
{
  string text = "Hello World";
  var thread = new Thread(
    () =>
    {
      Console.WriteLine(text); // variable read by worker thread
    });
  thread.Start();
  Console.WriteLine(text); // variable read by main thread
}

Synchronization primitives

public static void Main()
{
  var lockObj = new Object();
  int x = 0;
  var thread = new Thread(
    () =>
    {
      while (true)
      {
        lock (lockObj) // blocks until main thread releases the lock
        {
          x++;
        }
      }
    });
  thread.Start();
  while (true)
  {
    lock (lockObj) // blocks until worker thread releases the lock
    {
      x++;
      Console.WriteLine(x);
    }
  }
}

Events

public static void Main()
{
  var are = new AutoResetEvent(false);
  var thread = new Thread(
    () =>
    {
      while (true)
      {
        Thread.Sleep(1000);
        are.Set(); // worker thread signals the event
      }
    });
  thread.Start();
  while (are.WaitOne()) // main thread waits for the event to be signaled
  {
    Console.WriteLine(DateTime.Now);
  }
}