C# ThreadStart and ParameterizedThreadStart

Use ThreadStart and ParameterizedThreadStart to make a new thread.

ThreadStart. This specifies a target method. It does not support any arguments to the method. We use ThreadStart to begin running a thread.Threads

We use the ThreadStart type. We create an instance of it and pass that to the Thread constructor. We also use ParameterizedThreadStart.

This example C# program creates an array of 4 different threads. It starts a parameterless method on each thread. It then joins the threads together in a sequential order.Thread Join

Next: ThreadStart is created with a constructor that receives a target function name. This target method must not receive any parameters.

Then: The ThreadStart instance is passed as an argument to the Thread constructor.

Constructor

C# program that uses ThreadStart using System; using System.Threading; class Program { static void Main() { // Create an array of Thread references. Thread[] array = new Thread[4]; for (int i = 0; i < array.Length; i++) { // Start the thread with a ThreadStart. ThreadStart start = new ThreadStart(Start); array[i] = new Thread(start); array[i].Start(); } // Join all the threads. for (int i = 0; i < array.Length; i++) { array[i].Join(); } Console.WriteLine("DONE"); } static void Start() { // This method has no formal parameters. Console.WriteLine("Start()"); } } Output Start() Start() Start() Start() DONE

ParameterizedThreadStart. This starts a thread with a target method. We can then pass this instance to the Thread constructor. The target method is then invoked upon starting the Thread.

Example: We create 4 ParameterizedThreadStarts, then start and join 4 threads. Start() is executed 4 different times on separate threads.

Tip: With ParameterizedThreadStart, you pass a function name as the argument. This is an object type that you can later cast.

Info: The threads were called in a non-sequential order. There is a pause before the runtime can receive a thread.

Note: You can't count on the order of execution exactly here. A thread may take longer for reasons beyond your control.

C# program that uses ParameterizedThreadStart using System; using System.Threading; class Program { static void Main() { // Create an array of Thread references. Thread[] array = new Thread[4]; for (int i = 0; i < array.Length; i++) { // Start the thread with a ParameterizedThreadStart. ParameterizedThreadStart start = new ParameterizedThreadStart(Start); array[i] = new Thread(start); array[i].Start(i); } // Join all the threads. for (int i = 0; i < array.Length; i++) { array[i].Join(); } Console.WriteLine("DONE"); } static void Start(object info) { // This receives the value passed into the Thread.Start method. int value = (int)info; Console.WriteLine(value); } } Output 1 0 2 3 DONE

No parameters. What if you want to start a thread but don't need to pass any parameters to it? You don't need to pass the null literal.

Instead: You can use the ThreadStart type, which (fortunately) is detailed also on this page.

A summary. ThreadStart enables you to start a thread and pass no arguments to the target method. For parameterless target methods, this type is ideal.

ParameterizedThreadStart gives you the ability to pass an argument of any type to a specific method on a thread. We can process many different data values on different threads.

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C# ThreadStart and ParameterizedThreadStart

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