C# Joining Threads

In C#, multiple threads can be created and run concurrently to perform parallel tasks. Sometimes it is necessary to wait for one thread to finish its execution before proceeding or for all threads to complete before continuing further. The Thread.Join() method allows one thread to wait for another thread's completion, ensuring proper synchronization.

1. Thread.Join() Method

The Join method of the Thread class waits for the thread to complete its execution before continuing with the execution of the calling thread. This method blocks the calling thread until the target thread has completed its execution.

Syntax:

public void Join();

public bool Join(int millisecondsTimeout);

public bool Join(TimeSpan timeout);

• Join(): It blocks the calling thread until the target thread terminates.
• Join(int millisecondsTimeout): It waits for the specified duration (in milliseconds) or until the thread terminates, whichever occurs first.
• Join(TimeSpan timeout): It is similar to the above but uses TimeSpan.

Example:

Thread 2 started.
Thread 1 started.
Main Thread execution completed.

Overloaded Methods in Thread.join()

Thread class provides the Join() method, which allows one thread to wait until another thread completes its execution. If "t" is a Thread object, "t.Join()" causes the current thread to pause its execution until the thread represented by "t" terminates. There are some versions of in Join() method which provide more control on Threads. The Join() method has the following overloads:

• Join() Method
• Join(Int32) Method
• Join(TimeSpan) Method

1. Join() Method

This method blocks the calling thread until the thread represented by this instance terminates while continuing to perform standard COM (Component Object Model) and SendMessage pumping.

Syntax:

public void Join ();

2. Join(Int32) Method

This method blocks the calling thread for the specified number of milliseconds or until the target thread terminates, whichever occurs first. Returns true if the target thread terminates before the timeout expires, false otherwise.

Syntax:

public bool Join (int millisecondsTimeout);

3. Join(TimeSpan) Method

This method blocks the calling thread for the specified duration or until the target thread terminates, whichever occurs first. Returns true if the target thread terminates before the timeout expires, false otherwise.

Syntax:

public bool Join (TimeSpan timeout);

Example 1:

0
1
2
3
2nd thread is Working..

Explanation: In the above example,

• We have a non-static method, i.e. mythread() and mythread1(). So we create an instance, i.e. "o" of ExThread class and refer it in the constructor of ThreadStart class.
• Using Thread t1 = new Thread(new ThreadStart(o.mythread)); statement we create a thread named as t1 and initialize the work of this thread, similarly for thread t2.
• By using t1.Join(); statement, we will send the calling of t2 into waiting until the work of t1 thread is completed.
• After that t2 thread executes.

Example 2:

New thread is terminated

2. Task.WaitAll()

The WaitAll method of the Task class waits for all the specified tasks to complete before continuing with the execution of the calling thread. This method blocks the calling thread until all the specified tasks have completed their execution.

Example: