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Multithreading in C#

On July 26, 2011 Articles | Multithreading in C#
In this article we will learn how to create threads in C#, start and stop them and define their priorities.
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Multithreading
 
Multithreading is used to perform multiple tasks at the same time. Tasks with the potential of holding up other tasks can execute on separate threads, a process known as multithreading. Or, it's basically trying to do more than one thing at a time within a process.
 

Namespace

 
In .NET, threading functionality is defined in the System.Threading namespace. So you have to define System.Threading namespace before using any thread classes.
 

using System.Threading;

 

Starting a Thread

 
A C# client program starts in a single thread created automatically by the CLR and operating system that is called the main thread, and is made multithreaded by creating additional threads. Here's a simple example and its output.
 

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading;

 

namespace multi

{

    class Program

    {

        static void Main(string[] args)

        {

            Thread th = new Thread(WriteY);

            th.Start();

            for (int i = 0; i <= 10; i++)

            {

                Console.WriteLine("Hello");

            }

        }

        private static void WriteY()

        {

            for (int i = 0; i <= 9; i++)

            {

                Console.Write("world");

            }

        }

 

    }

}

OUTPUT

  starting thread

In the above example, the main thread creates a new thread on which it runs a method that repeatedly prints the string "world". Simultaneously, the main thread repeatedly prints the string "Hello".
 

Abort a Thread

 
The Thread class's Abort method is called to abort a thread. Make sure you check the IsAlive property before Abort.
 

if (Thread.IsAlive)
{

    Thread.Abort();

}

 

Here's a simple example and its output.

 

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading;

 

namespace multi

{

    class Program

    {

        static void Main(string[] args)

        {

            Thread th = new Thread(WriteY);

            if (th.IsAlive)

            {

                th.Start();

                th.Abort();

            }

 

            for (int i = 0; i <= 10; i++)

            {

                Console.WriteLine("Hello");

            }

        }

        private static void WriteY()

        {

            for (int i = 0; i <= 9; i++)

            {

                Console.WriteLine("world");

            }

 

        }

    }

 

}

 

OUTPUT

 

Stop thread

In the above example, The main thread creates a new thread which is stopped by the abort method. The main thread repeatedly prints the string "Hello".


Pausing a Thread

The Thread.Sleep method can be used to pause a thread for a fixed period of time.

Thread.Sleep() 

Here's a simple example and its output.

 

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading;

 

namespace multi

{

    class Program

    {

        static void Main(string[] args)

        {

            Thread th = new Thread(WriteY);

            th.Start();

            for (int i = 0; i <= 10; i++)

            {

                Console.WriteLine("Hello");

                Thread.Sleep(1000);

            }

        }

 

        private static void WriteY()

        {

            for (int i = 0; i <= 9; i++)

            {

                Console.WriteLine("world");

                Thread.Sleep(500);

            }

 

        }

 

    }

 

}

 

OUTPUT


Pause a thead

In the above example, the main thread creates a new thread which is paused by the Sleep method for 500 milliseconds. The main thread is also paused by a Sleep method for 1000 milliseconds.

 

Thread Priority

 
The Thread class's ThreadPriority property is used to set the thread's priority. The thread priority can have Normal, AboveNormal, BelowNormal, Highest, and Lowest values.
 
thread.Priority = ThreadPriority.Lowest

Here's a simple example without priority and its output.

 

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading;

 

namespace multi

{

    class Program

    {

        static void Main(string[] args)

        {

            Thread th = new Thread(WriteY);

            th.Start();

            for (int i = 0; i <= 10; i++)

            {

                Console.WriteLine("Hello");

            }

        }

 

        private static void WriteY()

        {

            for (int i = 0; i <= 9; i++)

            {

                Console.WriteLine("world");

            }

        }

    }

}

 

OUTPUT

 

Without priority thread

 

Using With Lowest Priority

 

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading;

 

namespace multi

{

    class Program

    {

        static void Main(string[] args)

        {

            Thread th = new Thread(WriteY);

            th.Priority = ThreadPriority.Lowest;

            th.Start();

            for (int i = 0; i <= 10; i++)

            {

                Console.WriteLine("Hello");

            }

        }

 

        private static void WriteY()

        {

            for (int i = 0; i <= 9; i++)

            {

                Console.WriteLine("world");

            }

        }

    }

}

 

OUTPUT


With priority thread

 

In the above example defines the priority, the without priority example executes the method writeY() but in the second example we defined the lowest priority it will execute main method first. 

 

Suspend a Thread

 
The Suspend method of the Thread class suspends a thread. The thread is suspended until the Resume method is called.
 

if (thread.ThreadState == ThreadState.Running)
{

       thread.Suspend();

}

 

Resume a suspended Thread

The Resume method is called to resume a suspended thread. If the thread is not suspended, the Resume method will have no effect.
 

if (thread.ThreadState == ThreadState.Suspended) {

       thread.Resume();

}

Conclusion

 
Multithreading is very useful to perform multiple tasks at the same time. If there is any mistake in this article then please notify me. I expect your valuable comments and feedback about this article.

Rohatash Kumar

Normal 0 false false false EN-AU X-NONE X-NONE I am a Microsoft .NET software Developer and author and C# Corner MVP. I h...

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