`ThreadStart`

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

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.

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.

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()");
    }
}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.

Detail 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.

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);
    }
}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.

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

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.