Multithreading with C#

End Module

In the above code I have used a separate thread to execute my run method. When code executes you can see the output



Sub thread increases the value within its run method and the main thread decreases its value one after the other.

Here's the part we have created a new thread and assigned job to done.

// create thread start delegate instance - contains the method to execute by the thread
ThreadStart ts = new ThreadStart(run);
// create new thread
Thread thrd = new Thread(ts);
// start thread
thrd.Start();

In here the thread start delegate is optional and we can directly create the thread like this as well

// create new thread
Thread thrd = new Thread(run);
// start thread
thrd.Start();

Note: This is C# language shortcut and does not available with VB.net.

Make the thread a background thread

This thread remains runing even the main thread finishes it's job, to finalize all the threads when main thread dies you have to set the IsBackground property to true.

// create new thread with ParameterizedThreadStart delegate instance
Thread thrd = new Thread(run);
// make the thread background
thrd.IsBackground = true;
// start thread with passing the parameters need
thrd.Start();

Passing parameters to the threads

If you want to pass any parameters to the method which is used to execute by the new thread then you can use the ParamerizedThreadStart delegate instead of the ThreadStart delegate.

Example: Using ParameterizedThreadStart to invoke methods with parameters

ParameterizedThreadStart which we used to execute our method by a separate thread looks like this

public delegate void ParameterizedThreadStart(object obj);

So we have to change our run method like this (matches with the ParameterizedThreadStart)

/* this method executed by a separate thread
* this sholud be match with the ParameterizedThreadStart
* (parameters must be passed as an object)
*/
static void run(object args)
{
// cast our parameter
int j = (int)args;

for (int i = 0; i < j; i++)
{
Console.WriteLine("Sub Thread value is : " + i);
Thread.Sleep(1000);
}
Console.WriteLine("Good Bye!!!I'm Sub Thread");
}

Executing part is like this (please read the comments)

// create new thread with ParameterizedThreadStart delegate instance
Thread thrd = new Thread(new ParameterizedThreadStart(run));
// start thread with passing the parameters need
thrd.Start(10);

Assigning Thread pool class to get the job done

By using the threadpool class we can assign our work to done by a separate thread easily and this is the way recommended using whenever possible.

Example: Using Threadpool class

// assign thread pool thread to do the job
ThreadPool.QueueUserWorkItem(run);

If you want to pass any parameters to the method executing by the thread you can pass them as a second argument.like this for our run method with object parameter.

// assign thread pool thread to do the job
ThreadPool.QueueUserWorkItem(run,10);

Complete code

class Program
{
static void Main(string[] args)
{
// assign thread pool thread to do the job
ThreadPool.QueueUserWorkItem(run,10);

// makes the main thread sleep - let sub thread to run
Thread.Sleep(1000);

for (int t = 10; t > 0; t--)
{
Console.WriteLine("Main Thread value is :" + t);
Thread.Sleep(1000);
}

Console.WriteLine("Good Bye!!!I'm main Thread");
Console.ReadLine();

}

/* this method executed by a separate thread
* this sholud be match with the WaitCallback
* (parameters must be passed as an object)
*/
static void run(object args)
{
// cast our parameter
int j = (int)args;

for (int i = 0; i < j; i++)
{
Console.WriteLine("Sub Thread value is : " + i);
Thread.Sleep(1000);
}
Console.WriteLine("Good Bye!!!I'm Sub Thread");
}
}


Periodic operations from threads

If you want to perform any method call in a perodic order then you can use the Timer class.

Note : There are three timer classes availbale with .net framework class library one is in System namespace next is in System.Windows.Forms namespace and the last is in System.Threading namespace all of them are providing similar functinalties so please don't confuse them together,I'm talking here is about the System.Threading.Timer class

Example: Using Timer class

class Program
{
static void Main(string[] args)
{
// assign thread timer to do the job
System.Threading.Timer thrdTimer = new Timer(run, 10, 0, 1000);

// makes the main thread sleep - let sub thread to run
Thread.Sleep(1000);

Console.WriteLine("Good Bye!!!I'm main Thread");
Console.ReadLine();

}