Thread.IsBackground Properti

Definisi

Ruang nama:

System.Threading

Rakitan:

netstandard.dll, System.Threading.Thread.dll

Sumber:

Thread.CoreCLR.cs

Mendapatkan atau menetapkan nilai yang menunjukkan apakah utas adalah utas latar belakang atau tidak.

public:
 property bool IsBackground { bool get(); void set(bool value); };

public bool IsBackground { get; set; }

member this.IsBackground : bool with get, set

Public Property IsBackground As Boolean

Nilai Properti

Boolean

true jika utas ini adalah atau menjadi utas latar belakang; jika tidak, false.

Pengecualian

ThreadStateException

Utasnya mati.

Contoh

Contoh berikut membedakan perilaku utas latar depan dan latar belakang. Ini membuat utas latar depan dan utas latar belakang. Utas latar depan membuat proses tetap berjalan sampai menyelesaikan perulangannya for dan berakhir. Namun, seperti yang ditunjukkan oleh output dari contoh, karena utas latar depan telah selesai dieksekusi, proses dihentikan sebelum utas latar belakang selesai dieksekusi.

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.

Keterangan

Utas adalah utas latar belakang atau utas latar depan. Utas latar belakang identik dengan utas latar depan, kecuali bahwa utas latar belakang tidak mencegah proses dihentikan. Setelah semua alur latar depan milik proses dihentikan, runtime bahasa umum mengakhiri proses. Utas latar belakang yang tersisa dihentikan dan tidak selesai.

Secara default, utas berikut dijalankan di latar depan (yaitu, propertinya IsBackground mengembalikan false):

• Utas utama (atau utas aplikasi utama).

• Semua utas yang dibuat dengan memanggil Thread konstruktor kelas.

Secara default, utas berikut dijalankan di latar belakang (yaitu, propertinya IsBackground mengembalikan true):

• Utas kumpulan utas, yang merupakan kumpulan utas pekerja yang dikelola oleh runtime. Anda dapat mengonfigurasi kumpulan utas dan menjadwalkan tugas pada utas dalam kumpulan tersebut dengan menggunakan kelas ThreadPool .

  Nota

  Operasi asinkron berbasis tugas secara otomatis dijalankan pada utas kumpulan utas.

• Semua utas yang memasuki lingkungan eksekusi terkelola dari kode yang tidak dikelola.

Lihat juga

• Utas Latar Depan dan Latar Belakang