Thread.Join Method ()


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Blocks the calling thread until the thread represented by this instance terminates, while continuing to perform standard COM and SendMessage pumping.

Namespace:   System.Threading
Assembly:  mscorlib (in mscorlib.dll)

[HostProtectionAttribute(SecurityAction.LinkDemand, Synchronization = true, 
	ExternalThreading = true)]
public void Join()

Exception Condition

The caller attempted to join a thread that is in the ThreadState.Unstarted state.


The thread is interrupted while waiting.

Join is a synchronization method that blocks the calling thread (that is, the thread that calls the method) until the thread whose Join method is called has completed. Use this method to ensure that a thread has been terminated. The caller will block indefinitely if the thread does not terminate. In the following example, the Thread1 thread calls the Join() method of Thread2, which causes Thread1 to block until Thread2 has completed.

using System;
using System.Threading;

public class Example
   static Thread thread1, thread2;

   public static void Main()
      thread1 = new Thread(ThreadProc);
      thread1.Name = "Thread1";

      thread2 = new Thread(ThreadProc);
      thread2.Name = "Thread2";

   private static void ThreadProc()
      Console.WriteLine("\nCurrent thread: {0}", Thread.CurrentThread.Name);
      if (Thread.CurrentThread.Name == "Thread1" && 
          thread2.ThreadState != ThreadState.Unstarted)

      Console.WriteLine("\nCurrent thread: {0}", Thread.CurrentThread.Name);
      Console.WriteLine("Thread1: {0}", thread1.ThreadState);
      Console.WriteLine("Thread2: {0}\n", thread2.ThreadState);
// The example displays output like the following:
//       Current thread: Thread1
//       Current thread: Thread2
//       Current thread: Thread2
//       Thread1: WaitSleepJoin
//       Thread2: Running
//       Current thread: Thread1
//       Thread1: Running
//       Thread2: Stopped

If the thread has already terminated when Join is called, the method returns immediately.


You should never call the Join method of the Thread object that represents the current thread from the current thread. This causes your app to hang because the current thread waits upon itself indefinitely,

This method changes the state of the calling thread to include ThreadState.WaitSleepJoin. You cannot invoke Join on a thread that is in the ThreadState.Unstarted state.

.NET Framework
Available since 1.1
Available since 2.0
Windows Phone Silverlight
Available since 7.0
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