Thread.IsBackground プロパティ

定義

スレッドがバックグラウンド スレッドであるかどうかを示す値を取得または設定します。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, set
Public Property IsBackground As Boolean

プロパティ値

このスレッドがバックグラウンド スレッドである場合またはバックグラウンド スレッドになる場合は true。それ以外の場合は falsetrue if this thread is or is to become a background thread; otherwise, false.

例外

スレッドが動作していませんThe thread is dead.

次の例では、フォアグラウンドスレッドとバックグラウンドスレッドの動作を比較しています。The following example contrasts the behavior of foreground and background threads. このメソッドは、フォアグラウンドスレッドとバックグラウンドスレッドを作成します。It creates a foreground thread and a background thread. フォアグラウンドスレッドは、for ループを完了して終了するまでプロセスを実行したままにします。The foreground thread keeps the process running until completes its for loop and terminates. ただし、この例の出力に示されているように、フォアグラウンドスレッドの実行が完了したため、バックグラウンドスレッドの実行が完了する前にプロセスが終了します。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.
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.

注釈

スレッドは、バックグラウンドスレッドまたはフォアグラウンドスレッドのいずれかです。A thread is either a background thread or a foreground thread. バックグラウンドスレッドは、プロセスが終了しないようにすることを除けば、フォアグラウンドスレッドと同じです。Background threads are identical to foreground threads, except that background threads do not prevent a process from terminating. プロセスに属するすべてのフォアグラウンドスレッドが終了すると、共通言語ランタイムによってプロセスが終了します。Once all foreground threads belonging to a process have terminated, the common language runtime ends the process. 残りのバックグラウンドスレッドは停止され、完了しません。Any remaining background threads are stopped and do not complete.

既定では、次のスレッドはフォアグラウンドで実行されます (つまり、IsBackground プロパティが falseを返します)。By default, the following threads execute in the foreground (that is, their IsBackground property returns false):

  • プライマリスレッド (またはメインアプリケーションスレッド)。The primary thread (or main application thread).

  • Thread クラスコンストラクターを呼び出すことによって作成されるすべてのスレッド。All threads created by calling a Thread class constructor.

既定では、次のスレッドがバックグラウンドで実行されます (つまり、IsBackground のプロパティが trueを返します)。By default, the following threads execute in the background (that is, their IsBackground property returns true):

  • スレッドプールスレッド。ランタイムによって管理されるワーカースレッドのプールです。Thread pool threads, which are a pool of worker threads maintained by the runtime. スレッドプールを構成し、ThreadPool クラスを使用してスレッドプールスレッドの作業をスケジュールすることができます。You can configure the thread pool and schedule work on thread pool threads by using the ThreadPool class.

    注意

    スレッドプールのスレッドでは、タスクベースの非同期操作が自動的に実行されます。Task-based asynchronous operations automatically execute on thread pool threads.

  • アンマネージコードからマネージ実行環境に入るすべてのスレッド。All threads that enter the managed execution environment from unmanaged code.

適用対象

こちらもご覧ください