Thread.IsBackground Property
Definition
Important
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Gets or sets a value indicating whether or not a thread is a background thread.
public:
property bool IsBackground { bool get(); void set(bool value); };public bool IsBackground { get; set; }member this.IsBackground : bool with get, setPublic Property IsBackground As BooleanProperty Value
true if this thread is or is to become a background thread; otherwise, false.
Exceptions
The thread is dead.
Examples
The following example contrasts the behavior of foreground and background threads. It creates a foreground thread and a background thread. The foreground thread keeps the process running until completes its for loop and terminates. However, as the output from the example shows, because the foreground thread has finished execution, the process is terminated before the background thread has completed execution.
using namespace System;
using namespace System::Threading;
ref class BackgroundTest
{
private:
int maxIterations;
public:
BackgroundTest(int maxIterations)
{
this->maxIterations = maxIterations;
}
void RunLoop()
{
for (int i = 0; i < maxIterations; i++ )
{
Console::WriteLine("{0} count: {1}",
Thread::CurrentThread->IsBackground ?
"Background Thread" : "Foreground Thread", i);
Thread::Sleep(250);
}
Console::WriteLine("{0} finished counting.",
Thread::CurrentThread->IsBackground ?
"Background Thread" : "Foreground Thread");
}
};
int main()
{
BackgroundTest^ shortTest = gcnew BackgroundTest( 10 );
Thread^ foregroundThread = gcnew Thread( gcnew ThreadStart( shortTest, &BackgroundTest::RunLoop ) );
foregroundThread->Name = "ForegroundThread";
BackgroundTest^ longTest = gcnew BackgroundTest( 50 );
Thread^ backgroundThread = gcnew Thread( gcnew ThreadStart( longTest, &BackgroundTest::RunLoop ) );
backgroundThread->Name = "BackgroundThread";
backgroundThread->IsBackground = true;
foregroundThread->Start();
backgroundThread->Start();
}
using System;
using System.Threading;
class Example
{
static void Main()
{
BackgroundTest shortTest = new BackgroundTest(10);
Thread foregroundThread =
new Thread(new ThreadStart(shortTest.RunLoop));
BackgroundTest longTest = new BackgroundTest(50);
Thread backgroundThread =
new Thread(new ThreadStart(longTest.RunLoop));
backgroundThread.IsBackground = true;
foregroundThread.Start();
backgroundThread.Start();
}
}
class BackgroundTest
{
int maxIterations;
public BackgroundTest(int maxIterations)
{
this.maxIterations = maxIterations;
}
public void RunLoop()
{
for (int i = 0; i < maxIterations; i++) {
Console.WriteLine("{0} count: {1}",
Thread.CurrentThread.IsBackground ?
"Background Thread" : "Foreground Thread", i);
Thread.Sleep(250);
}
Console.WriteLine("{0} finished counting.",
Thread.CurrentThread.IsBackground ?
"Background Thread" : "Foreground Thread");
}
}
// The example displays output like the following:
// Foreground Thread count: 0
// Background Thread count: 0
// Background Thread count: 1
// Foreground Thread count: 1
// Foreground Thread count: 2
// Background Thread count: 2
// Foreground Thread count: 3
// Background Thread count: 3
// Background Thread count: 4
// Foreground Thread count: 4
// Foreground Thread count: 5
// Background Thread count: 5
// Foreground Thread count: 6
// Background Thread count: 6
// Background Thread count: 7
// Foreground Thread count: 7
// Background Thread count: 8
// Foreground Thread count: 8
// Foreground Thread count: 9
// Background Thread count: 9
// Background Thread count: 10
// Foreground Thread count: 10
// Background Thread count: 11
// Foreground Thread finished counting.
open System.Threading
type BackgroundTest(maxIterations) =
member _.RunLoop() =
for i = 0 to maxIterations - 1 do
printfn
$"""{if Thread.CurrentThread.IsBackground then
"Background Thread"
else
"Foreground Thread"} count: {i}"""
Thread.Sleep 250
printfn
$"""{if Thread.CurrentThread.IsBackground then
"Background Thread"
else
"Foreground Thread"} finished counting."""
let shortTest = BackgroundTest 10
let foregroundThread = Thread shortTest.RunLoop
let longTest = BackgroundTest 50
let backgroundThread = Thread longTest.RunLoop
backgroundThread.IsBackground <- true
foregroundThread.Start()
backgroundThread.Start()
// The example displays output like the following:
// Foreground Thread count: 0
// Background Thread count: 0
// Background Thread count: 1
// Foreground Thread count: 1
// Foreground Thread count: 2
// Background Thread count: 2
// Foreground Thread count: 3
// Background Thread count: 3
// Background Thread count: 4
// Foreground Thread count: 4
// Foreground Thread count: 5
// Background Thread count: 5
// Foreground Thread count: 6
// Background Thread count: 6
// Background Thread count: 7
// Foreground Thread count: 7
// Background Thread count: 8
// Foreground Thread count: 8
// Foreground Thread count: 9
// Background Thread count: 9
// Background Thread count: 10
// Foreground Thread count: 10
// Background Thread count: 11
// Foreground Thread finished counting.
Imports System.Threading
Public Module Example
Public Sub Main()
Dim shortTest As New BackgroundTest(10)
Dim foregroundThread As New Thread(AddressOf shortTest.RunLoop)
Dim longTest As New BackgroundTest(50)
Dim backgroundThread As New Thread(AddressOf longTest.RunLoop)
backgroundThread.IsBackground = True
foregroundThread.Start()
backgroundThread.Start()
End Sub
End Module
Public Class BackgroundTest
Dim maxIterations As Integer
Sub New(maximumIterations As Integer)
maxIterations = maximumIterations
End Sub
Sub RunLoop()
For i As Integer = 0 To maxIterations
Console.WriteLine("{0} count: {1}", _
If(Thread.CurrentThread.IsBackground,
"Background Thread", "Foreground Thread"), i)
Thread.Sleep(250)
Next
Console.WriteLine("{0} finished counting.",
If(Thread.CurrentThread.IsBackground,
"Background Thread", "Foreground Thread"))
End Sub
End Class
' The example displays output like the following:
' Foreground Thread count: 0
' Background Thread count: 0
' Background Thread count: 1
' Foreground Thread count: 1
' Foreground Thread count: 2
' Background Thread count: 2
' Foreground Thread count: 3
' Background Thread count: 3
' Background Thread count: 4
' Foreground Thread count: 4
' Foreground Thread count: 5
' Background Thread count: 5
' Foreground Thread count: 6
' Background Thread count: 6
' Background Thread count: 7
' Foreground Thread count: 7
' Background Thread count: 8
' Foreground Thread count: 8
' Foreground Thread count: 9
' Background Thread count: 9
' Background Thread count: 10
' Foreground Thread count: 10
' Background Thread count: 11
' Foreground Thread finished counting.
Remarks
A thread is either a background thread or a foreground thread. Background threads are identical to foreground threads, except that background threads do not prevent a process from terminating. Once all foreground threads belonging to a process have terminated, the common language runtime ends the process. Any remaining background threads are stopped and do not complete.
By default, the following threads execute in the foreground (that is, their IsBackground property returns false):
The primary thread (or main application thread).
All threads created by calling a Thread class constructor.
By default, the following threads execute in the background (that is, their IsBackground property returns true):
Thread pool threads, which are a pool of worker threads maintained by the runtime. You can configure the thread pool and schedule work on thread pool threads by using the ThreadPool class.
Note
Task-based asynchronous operations automatically execute on thread pool threads.
All threads that enter the managed execution environment from unmanaged code.
