ThreadPriority 列舉

定義

命名空間:

System.Threading

組件:

System.Threading.Thread.dll

組件:

mscorlib.dll

組件:

netstandard.dll

指定 Thread 的排程優先權。

public enum class ThreadPriority

public enum ThreadPriority

[System.Serializable]
public enum ThreadPriority

[System.Serializable]
[System.Runtime.InteropServices.ComVisible(true)]
public enum ThreadPriority

type ThreadPriority = 

[<System.Serializable>]
type ThreadPriority = 

[<System.Serializable>]
[<System.Runtime.InteropServices.ComVisible(true)>]
type ThreadPriority = 

Public Enum ThreadPriority

繼承

Object

ValueType

Enum

ThreadPriority

屬性

SerializableAttribute ComVisibleAttribute

欄位

AboveNormal	3	Thread 可排定於具有 Highest 優先權的執行緒之後、具有 Normal 優先權的執行緒之前。
BelowNormal	1	Thread 可排定於具有 Normal 優先權的執行緒之後、具有 Lowest 優先權的執行緒之前。
Highest	4	Thread 可排定在具有任何他優先權的執行緒之前。
Lowest	0	Thread 可排定在具有任何其他優先權的執行緒之後。
Normal	2	Thread 可排定於具有 AboveNormal 優先權的執行緒之後、具有 BelowNormal 優先權的執行緒之前。 執行緒依預設具有 Normal 優先權。

範例

下列程式碼範例顯示變更執行緒優先順序的結果。 建立三個執行緒、一個執行緒的優先順序設定為 BelowNormal，而第二個執行緒的優先順序會設定為 AboveNormal。 每個執行緒都會遞增迴圈中的 while 變數，並在設定時間內執行。

using System;
using System.Threading;
using Timers = System.Timers;

class Test
{
    static void Main()
    {
        PriorityTest priorityTest = new PriorityTest();

        Thread thread1 = new Thread(priorityTest.ThreadMethod);
        thread1.Name = "ThreadOne";
        Thread thread2 = new Thread(priorityTest.ThreadMethod);
        thread2.Name = "ThreadTwo";
        thread2.Priority = ThreadPriority.BelowNormal;
        Thread thread3 = new Thread(priorityTest.ThreadMethod);
        thread3.Name = "ThreadThree";
        thread3.Priority = ThreadPriority.AboveNormal;

        thread1.Start();
        thread2.Start();
        thread3.Start();
        // Allow counting for 10 seconds.
        Thread.Sleep(10000);
        priorityTest.LoopSwitch = false;
    }
}

class PriorityTest
{
    static volatile bool loopSwitch;
    [ThreadStatic] static long threadCount = 0;

    public PriorityTest()
    {
        loopSwitch = true;
    }

    public bool LoopSwitch
    {
        set{ loopSwitch = value; }
    }

    public void ThreadMethod()
    {
        while(loopSwitch)
        {
            threadCount++;
        }
        Console.WriteLine("{0,-11} with {1,11} priority " +
            "has a count = {2,13}", Thread.CurrentThread.Name, 
            Thread.CurrentThread.Priority.ToString(), 
            threadCount.ToString("N0")); 
    }
}
// The example displays output like the following:
//    ThreadOne   with      Normal priority has a count =   755,897,581
//    ThreadThree with AboveNormal priority has a count =   778,099,094
//    ThreadTwo   with BelowNormal priority has a count =     7,840,984

Imports System.Threading
Imports Timers = System.Timers

Public Module Example
   Dim t As Timers.Timer
   Private priorityTest As New PriorityTest()

    Public Sub Main()
        Dim thread1 As New Thread(AddressOf priorityTest.ThreadMethod)
        thread1.Name = "ThreadOne"
        Dim thread2 As New Thread(AddressOf priorityTest.ThreadMethod)
        thread2.Name = "ThreadTwo"
        thread2.Priority = ThreadPriority.BelowNormal
        Dim thread3 As New Thread(AddressOf priorityTest.ThreadMethod)
        thread3.Name = "ThreadThree"
        thread3.Priority = ThreadPriority.AboveNormal
        thread1.Start()
        thread2.Start()
        thread3.Start()

        ' Allow threads to execute for about 10 seconds.
        t = New Timers.Timer()
        t.AutoReset = False
        t.Interval = 10000
        AddHandler t.Elapsed, AddressOf Elapsed
        t.Start()
    End Sub

    Private Sub Elapsed(sender As Object, e As Timers.ElapsedEventArgs)
       priorityTest.LoopSwitch = False
    End Sub
End Module

Public Class PriorityTest
    Private Shared loopSwitchValue As Boolean
    <ThreadStatic> Shared threadCount As Long

    Sub New()
        loopSwitchValue = True
    End Sub

    WriteOnly Property LoopSwitch As Boolean
        Set
            loopSwitchValue = Value
        End Set
    End Property

    Sub ThreadMethod()
        Do While True
            threadCount += 1
            If Not loopSwitchValue Then Exit Do
        Loop

        Console.WriteLine("{0,-11} with {1,11} priority " &
            "has a count = {2,13}", Thread.CurrentThread.Name,
            Thread.CurrentThread.Priority.ToString(),
            threadCount.ToString("N0")) 
    End Sub
End Class
' The example displays the following output:
'    ThreadOne   with      Normal priority has a count =   755,897,581
'    ThreadThree with AboveNormal priority has a count =   778,099,094
'    ThreadTwo   with BelowNormal priority has a count =     7,840,984

備註

ThreadPriority 會定義執行緒優先順序的所有可能值集合。 執行緒優先順序會指定一個執行緒與另一個執行緒的相對優先順序。

每個執行緒都有指派的優先順序。 在執行時間內建立的執行緒一開始會指派 Normal 優先順序，而執行時間外部建立的執行緒會在進入執行時間時保留其先前的優先順序。 您可以藉由存取其 Priority 屬性來取得和設定執行緒的優先順序。

執行緒會根據它們的優先權排定執行。 用來判斷線程執行順序的排程演算法會隨著每個作業系統而有所不同。 當使用者介面的焦點在前景與背景之間移動時，作業系統也可以動態調整執行緒優先順序。

執行緒的優先順序不會影響執行緒的狀態;執行緒的狀態必須在 Running 作業系統可以排程之前。

另請參閱

• Thread
• 排程執行緒