Thread.IsBackground Property

Property Value

Type: System.Boolean
true if this thread is or is to become a background thread; otherwise, false.

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
      outputBlock.Text = "Click here to begin the demo." & vbLf 

      AddHandler outputBlock.MouseLeftButtonUp, AddressOf MouseUp

   End Sub

   Private Shared Sub MouseUp(ByVal sender As Object, ByVal e As MouseButtonEventArgs)

      RemoveHandler outputBlock.MouseLeftButtonUp, AddressOf MouseUp
      outputBlock.Text = "To run the demo again, refresh the page." & vbLf & vbLf

      Dim backgroundThread As New Thread(AddressOf RunLoop)
      backgroundThread.Name = "BackgroundThread"
      backgroundThread.IsBackground = True
      backgroundThread.Start(Nothing)

      Dim foregroundThread As New Thread(AddressOf RunLoop)
      foregroundThread.Name = "ForegroundThread"
      foregroundThread.Start(Nothing)

      ThreadPool.QueueUserWorkItem(AddressOf RunLoop)

   End Sub

   Private Shared Sub RunLoop(ByVal State As Object)

      Dim threadName As String = Thread.CurrentThread.Name
      If threadName Is Nothing Then threadName = "<ThreadPool thread>"

      outputBlock.Dispatcher.BeginInvoke(displayHelper, _
         String.Format("{0} is running. IsBackground = {1}" & vbLf, _
         threadName, Thread.CurrentThread.IsBackground))

   End Sub

   ' In order to update the TextBlock object, which is on the UI thread, you must
   ' make a cross-thread call by using the Dispatcher object that is associated 
   ' with the TextBlock. The DisplayOutput helper method and its delegate, 
   ' displayHelper, are used by the BeginInvoke method of the Dispatcher object
   ' to append text to the TextBlock. 
   '
   Private Shared displayHelper As New Action(Of String)(AddressOf DisplayOutput)
   Private Shared Sub DisplayOutput(ByVal msg As String)
      outputBlock.Text &= msg 
   End Sub

End Class

' This example produces output similar to the following:
'
'BackgroundThread is running. IsBackground = True.
'ForegroundThread is running. IsBackground = False.
'<ThreadPool thread> is running. IsBackground = True.

using System;
using System.Threading;
using System.Windows.Input;

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

   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      Example.outputBlock = outputBlock;
      outputBlock.Text = "Click here to begin the demo.\n";

      outputBlock.MouseLeftButtonUp += new MouseButtonEventHandler(MouseUp);
   }

   private static void MouseUp(object sender, System.Windows.Input.MouseButtonEventArgs e)
   {
      outputBlock.MouseLeftButtonUp -= new MouseButtonEventHandler(MouseUp);
      outputBlock.Text = "To run the demo again, refresh the page.\n\n";

      Thread backgroundThread = new Thread(RunLoop);
      backgroundThread.Name = "BackgroundThread";
      backgroundThread.IsBackground = true;
      backgroundThread.Start(null);

      Thread foregroundThread = new Thread(RunLoop);
      foregroundThread.Name = "ForegroundThread";
      foregroundThread.Start(null);

      ThreadPool.QueueUserWorkItem(RunLoop);
   }

   private static void RunLoop(object state)
   {
      string threadName = Thread.CurrentThread.Name;
      if (threadName==null) {threadName = "<ThreadPool thread>";}

      outputBlock.Dispatcher.BeginInvoke(displayHelper, 
         String.Format("{0} is running. IsBackground = {1}\n", 
                       threadName, Thread.CurrentThread.IsBackground));
   }

   // In order to update the TextBlock object, which is on the UI thread, you must
   // make a cross-thread call by using the Dispatcher object that is associated 
   // with the TextBlock. The DisplayOutput helper method and its delegate, 
   // displayHelper, are used by the BeginInvoke method of the Dispatcher object
   // to append text to the TextBlock. 
   //
   private static Action<string> displayHelper = new Action<string>(DisplayOutput);
   private static void DisplayOutput(string msg)
   {
      outputBlock.Text += msg;
   }
}

/* This example produces output similar to the following:

BackgroundThread is running. IsBackground = True.
ForegroundThread is running. IsBackground = False.
<ThreadPool thread> is running. IsBackground = True.
 */