How to create Threads in C#

In C#, you can create threads using the System.Threading namespace. Here is an example code snippet:

C#

using System;
using System.Threading;

class Program {
    static void Main() {
        // Create a new thread and start it
        Thread thread = new Thread(new ThreadStart(Worker));
        thread.Start();

        // Do some work in the main thread
        for (int i = 0; i < 5; i++) {
            Console.WriteLine("Main thread: {0}", i);
            Thread.Sleep(100);
        }

        // Wait for the worker thread to finish
        thread.Join();
    }

    static void Worker() {
        // Do some work in the worker thread
        for (int i = 0; i < 5; i++) {
            Console.WriteLine("Worker thread: {0}", i);
            Thread.Sleep(100);
        }
    }
}

Output

Main thread: 0
Worker thread: 0
Main thread: 1
Worker thread: 1
Main thread: 2
Worker thread: 2
Main thread: 3
Worker thread: 3
Main thread: 4
Worker thread: 4

In this example, we create a new thread using the Thread class and passing in a delegate to the Worker method. We then start the thread using the Start method.

In the Main method, we do some work in the main thread and then wait for the worker thread to finish using the Join method.

In the Worker method, we do some work in the worker thread.

Note that when creating threads, you should always make sure to properly synchronize access to shared data between threads to avoid race conditions and other synchronization issues.

In C#, a multi-threading system is built upon the Thread class, which encapsulates the execution of threads. This class contains several methods and properties which helps in managing and creating threads and this class is defined under System.Threading namespace. The System.Threading namespace provides classes and interfaces that are used in multi-thread programming. Some commonly used classes in this namespace are :

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Class Name	Description
Mutex	It is a synchronization primitive that can also be used for IPS (interprocess synchronization).
Monitor	This class provides a mechanism that access objects in synchronize manner.
Semaphore	This class is used to limit the number of threads that can access a resource or pool of resources concurrently.
Thread	This class is used to creates and controls a thread, sets its priority, and gets its status.
ThreadPool	This class provides a pool of threads that can be used to execute tasks, post work items, process asynchronous I/O, wait on behalf of other threads, and process timers.
ThreadLocal	This class provides thread-local storage of data.
Timer	This class provides a mechanism for executing a method on a thread pool thread at specified intervals. You are not allowed to inherit this class.
Volatile	This class contains methods for performing volatile memory operations.

Steps to create a thread in a C# Program:

1. First of all import System.Threading namespace, it plays an important role in creating a thread in your program as you have no need to write the fully qualified name of class everytime.

Using System;
Using System.Threading

1. Now, create and initialize the thread object in your main method.

public static void main()
{
    Thread thr = new Thread(job1);
}

1. Or You can also use ThreadStart constructor for initializing a new instance.

public static void main()
{
     Thread thr = new Thread(new ThreadStart(job1));
}

1. Now you can call your thread object.

public static void main()
{
    Thread thr = new Thread(job1);
    thr.Start();
}

Below programs illustrate the practical implementations of above steps: Example 1:

CSharp

// C# program to illustrate the
// creation of thread using
// non-static method
using System;
using System.Threading;

public class ExThread {

    // Non-static method
    public void mythread1()
    {
        for (int z = 0; z < 3; z++) {
            Console.WriteLine("First Thread");
        }
    }
}

// Driver Class
public class GFG {

    // Main Method
    public static void Main()
    {
        // Creating object of ExThread class
        ExThread obj = new ExThread();

        // Creating thread
        // Using thread class
        Thread thr = new Thread(new ThreadStart(obj.mythread1));
        thr.Start();
    }
}

Output:

First Thread
First Thread
First Thread

Explanation: In the above example, we have a class named as ExThread that contain a non-static method named as mythread1(). So we create an instance, i.e. obj of ExThread class and refer it in the constructor of ThreadStart class as given in this statement Thread a = new Thread(new ThreadStart(obj.mythread1));. Using Thread a = new Thread(new ThreadStart(obj.mythread1)); statement we will create a thread named as thr and initialize the work of this thread. By using thr.Start(); statement. Example 2:

CSharp

// C# program to illustrate the creation
// of thread using static method
using System;
using System.Threading;

public class ExThread {

    // Static method for thread a
    public static void thread1()
    {
        for (int z = 0; z < 5; z++) {
            Console.WriteLine(z);
        }
    }

    // static method for thread b
    public static void thread2()
    {
        for (int z = 0; z < 5; z++) {
            Console.WriteLine(z);
        }
    }
}

// Driver Class
public class GFG {

    // Main method
    public static void Main()
    {
        // Creating and initializing threads
        Thread a = new Thread(ExThread.thread1);
        Thread b = new Thread(ExThread.thread2);
        a.Start();
        b.Start();
    }
}

Output :

0
1
2
3
4
0
1
2
3
4

Explanation: In the above example, we have a class named as ExThread and contain two static methods named as thread1() and thread2(). So we do not need to create an instance of ExThread class. Here we call these methods using a class name, like ExThread.thread1, ExThread.thread2. By using Thread a = new Thread(ExThread.thread1); statement we create and initialize the work of thread a, similarly for thread b. By using a.Start(); and b.Start(); statements, a and b threads scheduled for execution. Note: The output of these programs may vary due to context switching.