Thread Class

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

Creates and controls a thread, and gets its status.

Inheritance Hierarchy

System..::.Object
System.Threading..::.Thread

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

Syntax

Public NotInheritable Class Thread
public sealed class Thread

The Thread type exposes the following members.

Constructors

Name Description
Thread(ParameterizedThreadStart) Initializes a new instance of the Thread class, specifying a delegate that allows an object to be passed to the thread when the thread is started.
Thread(ThreadStart) Initializes a new instance of the Thread class.

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Properties

Name Description
CurrentCulture Gets or sets the culture for the current thread.
CurrentThread Gets the currently running thread.
CurrentUICulture Gets or sets the current culture used by the Resource Manager to look up culture-specific resources at run time.
IsAlive Gets a value that indicates the execution status of the current thread.
IsBackground Gets or sets a value that indicates whether a thread is a background thread.
ManagedThreadId Gets a unique identifier for the current, managed thread.
Name Gets or sets the name of the thread.
ThreadState Gets a value that contains the states of the current thread.

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Methods

Name Description
Abort Security Critical. Raises a ThreadAbortException in the thread on which it is invoked, to begin the process of terminating the thread. Calling this method usually terminates the thread.
Equals(Object) Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
Finalize Allows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
GetDomain Returns the current domain in which the current thread is running.
GetHashCode Returns a hash code for the current thread. (Overrides Object..::.GetHashCode()()().)
GetType Gets the Type of the current instance. (Inherited from Object.)
Join()()() Blocks the calling thread until a thread terminates, while continuing to perform standard COM and SendMessage pumping.
Join(Int32) Blocks the calling thread until a thread terminates or the specified time elapses, while continuing to perform standard COM and SendMessage pumping.
MemberwiseClone Creates a shallow copy of the current Object. (Inherited from Object.)
MemoryBarrier Ensures that memory accesses that appear before the call to MemoryBarrier, in program order, will not execute after the call to MemoryBarrier, and that memory accesses that appear after the call to MemoryBarrier will not execute before that call.
Sleep(Int32) Suspends the current thread for a specified time.
Sleep(TimeSpan) Blocks the current thread for a specified time.
SpinWait Causes a thread to wait the number of times defined by the iterations parameter.
Start()()() Causes the operating system to change the state of the current instance to ThreadState..::.Running.
Start(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 that the thread executes.
ToString Returns a string that represents the current object. (Inherited from Object.)

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Remarks

A process can create one or more threads to execute portions of the program code associated with the process. The unit of execution for managed threads is the method. Use a ThreadStart delegate or the ParameterizedThreadStart delegate to specify the method executed by a thread. The ParameterizedThreadStart delegate allows you to pass data to the thread procedure as a parameter.

For the duration of its existence, a thread is always in one or more of the states defined by ThreadState.

The ManagedThreadId property provides identification for managed threads. For the lifetime of your thread, it will not collide with the value from any other thread, regardless of the application domain from which you obtain the value.

Note

An operating-system thread ID has no fixed relationship to a managed thread, because an unmanaged host can control the relationship between managed and unmanaged threads.

It is not necessary to retain a reference to a Thread object once you have started the thread. The thread continues to execute until the thread procedure is complete.

It is not necessary to create threads yourself. The BackgroundWorker and ThreadPool classes enable you to use system-managed background threads in a simple, task-oriented way. For background tasks that return results to the user interface (UI) thread, the simplest programming technique is to use the BackgroundWorker class. The following table lists some sources of information on various kinds of concurrent programming.

Task

See

Execute a background task that communicates with the main application thread by using events.

BackgroundWorker

Execute a background task that has little or no need to communicate with the main application thread.

The Managed Thread Pool

Protect regions of code or fields from concurrent access.

Monitor; the Visual Basic SyncLock statement (lock statement in C#)

Synchronize the activities of multiple threads.

EventWaitHandle, AutoResetEvent, and ManualResetEvent

Execute code in the background at regular intervals.

Timer

Execute code on the UI thread at regular intervals.

DispatcherTimer

Provide lock-free concurrent access to data.

Interlocked Operations

Create your own threads.

Thread class.

Examples

This section contains two examples. The first example shows how to create a thread that executes a static method. The second example shows how to create a thread that executes an instance method.

The examples display their output in a TextBlock on the UI thread. To access the TextBlock from the callback thread, the examples use the Dispatcher property to obtain a Dispatcher object for the TextBlock, and then use the Dispatcher..::.BeginInvoke method to make the cross-thread call.

For examples of coordinating the actions of threads with wait handles, see EventWaitHandle. For examples of coordinating the actions of threads with critical sections (lock in C#, SyncLock in Visual Basic), see Monitor. For examples of how to use thread pool threads, see BackgroundWorker, ThreadPool, and Timer.

Example 1

The following example shows how to create a thread that executes a static method.

Note

For information on how to compile and run this example code, see Building examples that have static TextBlock controls for Windows Phone 8.

Imports System.Threading

Public Class Example

   Private Shared outputBlock As System.Windows.Controls.TextBlock

   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)

      Example.outputBlock = outputBlock

      ' To start a thread using a static thread procedure, use the
      ' class name and method name when you create the ThreadStart
      ' delegate. Visual Basic expands the AddressOf expression 
      ' to the appropriate delegate creation syntax:
      '    New ThreadStart(AddressOf Example.DoWork)
      '
      Dim newThread As New Thread(AddressOf Example.DoWork)
      newThread.Start()

   End Sub

   ' 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 Shared Sub DoWork()
      Dim display As New Action(Of String)(AddressOf DisplayOutput)

      outputBlock.Dispatcher.BeginInvoke(display, _
         "Hello from a Shared thread procedure." & vbCrLf)
   End Sub

   ' The Dispatcher.BeginInvoke method runs this helper method on the 
   ' UI thread, so it can safely access the TextBlock that is used to 
   ' display the output.
   Private Shared Sub DisplayOutput(msg)
      outputBlock.Text &= msg
   End Sub

End Class

' This code example produces the following output:
'
'Hello from a Shared thread procedure.
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 static thread procedure, use the
      // class name and method name when you create the ThreadStart
      // delegate. C# expands the method name to the appropriate 
      // delegate creation syntax:
      //    New ThreadStart(Example.DoWork)
      //
      Thread newThread = new Thread(Example.DoWork);
      newThread.Start();
   }

   // 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()
   {
      outputBlock.Dispatcher.BeginInvoke(delegate () { 
         outputBlock.Text += "Hello from a static thread procedure.\n"; 
      });
   }
}

/* This code example produces the following output:

Hello from a static thread procedure.
 */

Example 2

The following example shows how to create a thread that executes an instance method.

Note

For information on how to compile and run this example code, see Building examples that have static TextBlock controls for Windows Phone 8.

Imports System.Threading

Public Class Example

   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)

      ' To start a thread using an instance method for the thread 
      ' procedure, use the instance variable and method name when 
      ' you create the ThreadStart delegate. Visual Basic expands 
      ' the AddressOf expression to the appropriate delegate 
      ' creation syntax:
      '    New ThreadStart(AddressOf w.DoMoreWork)
      '
      Dim w As New Work()
      w.Data = 42
      w.Output = outputBlock

      Dim newThread As Thread = New Thread(AddressOf w.DoMoreWork)
      newThread.Start()
   End Sub

End Class

Public Class Work
   Public Data As Integer
   Public Output As System.Windows.Controls.TextBlock

   ' 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.
   Public Sub DoMoreWork()
      Dim display As New Action(Of String)(AddressOf DisplayOutput)

      Output.Dispatcher.BeginInvoke(display, _
         String.Format("Instance thread procedure. Data={0}", Data) & vbCrLf)
   End Sub

   ' The Dispatcher.BeginInvoke method runs this helper method on the 
   ' UI thread, so it can safely access the TextBlock that is used to 
   ' display the output.
   Private Sub DisplayOutput(msg)
      Output.Text &= msg
   End Sub

End Class

' This code example produces the following output:
'
'Instance thread procedure. Data=42
using System;
using System.Threading;

public class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      // To start a thread using an instance method for the thread 
      // procedure, use the instance variable and method name when 
      // you create the ThreadStart delegate. C# expands the object
      // reference and method name to the appropriate delegate 
      // creation syntax:
      //    New ThreadStart(AddressOf w.DoMoreWork)
      //
      Work w = new Work();
      w.Data = 42;
      w.Output = outputBlock;

      Thread newThread = new Thread(w.DoMoreWork);
      newThread.Start();
   }
}

public class Work
{
   public int Data;
   public System.Windows.Controls.TextBlock Output;

   // 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.
   public void DoMoreWork()
   {
      Output.Dispatcher.BeginInvoke(delegate () {
         Output.Text += String.Format("Instance thread procedure. Data={0}\n", Data);
      });
   }
}

// This code example produces the following output:
//
//Instance thread procedure. Data=42

Version Information

Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Platforms

Windows Phone

Thread Safety

This type is thread safe.

See Also

Reference

System.Threading Namespace

Other Resources

Managed Threading Overview

Managed Threading Overview

Best Practices for Managed Threading

Threading Objects and Features

Synchronization Primitives