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Thread.Start Method

Causes the operating system to change the state of the current instance to ThreadState.Running.

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

[HostProtectionAttribute(SecurityAction.LinkDemand, Synchronization = true, 
	ExternalThreading = true)]
public void Start()


The thread has already been started.


There is not enough memory available to start this thread.

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 represented by the ThreadStart or ParameterizedThreadStart delegate supplied to the thread constructor.


If this overload is used with a thread created using a ParameterizedThreadStart delegate, null is passed to the method executed by the thread.

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


The HostProtectionAttribute attribute applied to this type or member has the following Resources property value: Synchronization | ExternalThreading. The HostProtectionAttribute does not affect desktop applications (which are typically started by double-clicking an icon, typing a command, or entering a URL in a browser). For more information, see the HostProtectionAttribute class or SQL Server Programming and Host Protection Attributes.

The following code example demonstrates creating a thread and starting it.

This code produces the following output:

     In main.
     Working thread...
     In main. Working thread...
     In main.
     Working thread...

Note that the sequence of the output statements is typical, but is not guaranteed to be identical across systems.

Thread procedures can be static methods or instance methods. See the code example provided for the ThreadStart delegate. For more information about thread creation, see Creating Threads and Passing Data at Start Time.

using System;
using System.Threading;

public class ThreadWork 
   public static void DoWork()
      for(int i = 0; i<3;i++)
         Console.WriteLine("Working thread...");
class ThreadTest
   public static void Main()
      ThreadStart myThreadDelegate = new ThreadStart(ThreadWork.DoWork);
      Thread myThread = new Thread(myThreadDelegate);
         for(int i = 0; i<3; i++)
         Console.WriteLine("In main.");

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Community Additions

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