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Thread.Start Method (Object)

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 the thread executes.

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

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

Parameters

parameter
Type: System.Object

An object that contains data to be used by the method the thread executes.

ExceptionCondition
ThreadStateException

The thread has already been started.

OutOfMemoryException

There is not enough memory available to start this thread.

InvalidOperationException

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

NoteNote:

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.

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.

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 code example shows the syntax for creating and using a ParameterizedThreadStart delegate with a static method and an instance method.

using System;
using System.Threading;

public class Work
{
    public static void Main()
    {
        // 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(Work.DoWork) 
        //
        Thread newThread = new Thread(Work.DoWork);

        // Use the overload of the Start method that has a 
        // parameter of type Object. You can create an object that 
        // contains several pieces of data, or you can pass any  
        // reference type or value type. The following code passes 
        // the integer value 42. 
        //
        newThread.Start(42);

        // To start a thread using an instance method for the thread  
        // procedure, use the instance variable and method name when  
        // you create the ParameterizedThreadStart delegate. C# infers  
        // the appropriate delegate creation syntax: 
        //    new ParameterizedThreadStart(w.DoMoreWork) 
        //
        Work w = new Work();
        newThread = new Thread(w.DoMoreWork);

        // Pass an object containing data for the thread. 
        //
        newThread.Start("The answer.");
    }

    public static void DoWork(object data)
    {
        Console.WriteLine("Static thread procedure. Data='{0}'",
            data);
    }

    public void DoMoreWork(object data)
    {
        Console.WriteLine("Instance thread procedure. Data='{0}'",
            data);
    }
}

/* This code example produces the following output (the order 
   of the lines might vary):

Static thread procedure. Data='42'
Instance thread procedure. Data='The answer'
*/

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

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

.NET Framework

Supported in: 3.5, 3.0, 2.0

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