Start Method (Object)
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Thread.Start Method (Object)

[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]

Causes the operating system to change the state of the current instance to ThreadState.Running, and optionally supplies an object containing data to be used by the method that the thread executes.

Namespace:  System.Threading
Assembly:  mscorlib (in mscorlib.dll)

public void Start(
	Object parameter


Type: System.Object
An object that contains data to be used by the method that the thread executes.


The thread has already been started.


There is not enough memory available to start this thread.


This thread was created by using a ThreadStart delegate instead of a ParameterizedThreadStart delegate.

Once a thread is in the ThreadState.Running state, the operating system can schedule it for execution. The thread begins executing at the first line of the method that is represented by the ThreadStart or ParameterizedThreadStart delegate supplied to the thread constructor.

Once the thread terminates, it cannot be restarted with another call to Start.

This overload and the ParameterizedThreadStart delegate make it easy to pass data to a thread procedure, but the technique is not type safe because any object can be passed to this overload. A more robust way to pass data to a thread procedure is to put both the thread procedure and the data fields into a worker object. For more information, see Creating Threads and Passing Data at Start Time.

The following example shows how to create and start a thread that executes a static method and passes data to the method.

The example displays its output in a TextBlock on the user interface (UI) thread. To access the TextBlock from the callback thread, the example uses the Dispatcher property to obtain a Dispatcher object for the TextBlock, and then uses the Dispatcher.BeginInvoke method to make the cross-thread call.

For more information about thread creation, see Creating Threads and Passing Data at Start Time. For additional examples of how to pass thread synchronization objects to thread procedures, see EventWaitHandle.

using System;
using System.Threading;

public class Example
   private static System.Windows.Controls.TextBlock outputBlock;

   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
      Example.outputBlock = outputBlock;

      // To start a thread using a shared thread procedure, use
      // the class name and method name when you create the 
      // ParameterizedThreadStart delegate. C# infers the 
      // appropriate delegate creation syntax:
      //    New ParameterizedThreadStart(Example.DoWork)
      Thread newThread = new Thread(Example.DoWork);

   // Simulate work. To communicate with objects on the UI thread, get the 
   // Dispatcher for one of the UI objects. Use the Dispatcher object's 
   // BeginInvoke method to queue a delegate that will run on the UI thread,
   // and therefore can safely access UI elements like the TextBlock.
   private static void DoWork(object state)
      int data = (int) state;

      outputBlock.Dispatcher.BeginInvoke(delegate () { 
         outputBlock.Text += String.Format("Static thread procedure. Data={0}\n", data); 

/* This code example produces the following output:

Static thread procedure. Data=42

Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

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