ThreadPriority 列舉

定義

命名空間:

System.Threading

組件:

netstandard.dll, System.Threading.Thread.dll

來源:

ThreadPriority.cs

指定 Thread的排程優先順序。

public enum class ThreadPriority

public enum ThreadPriority

type ThreadPriority = 

Public Enum ThreadPriority

繼承

Object

ValueType

Enum

ThreadPriority

欄位

名稱	值	Description
Lowest	0	這些可以 Thread 排程在執行緒之後，並有其他優先權。
BelowNormal	1	這些可以 Thread 排程在有 Normal 優先權的執行緒之後，也可以排在有 Lowest 優先順序的執行緒之前。
Normal	2	這些可以 Thread 排程在有 AboveNormal 優先權的執行緒之後，也可以排在有 BelowNormal 優先順序的執行緒之前。 執行緒預設有 Normal 優先權。
AboveNormal	3	這些可以 Thread 排程在有 Highest 優先權的執行緒之後，也可以排在有 Normal 優先順序的執行緒之前。
Highest	4	它們 Thread 可以排程在執行緒之前，且有其他優先順序。

範例

以下程式碼範例展示了更改執行緒優先順序的結果。 會建立三個執行緒，其中一個執行緒的優先權設為 BelowNormal，另一個執行緒的優先權設為 AboveNormal。 每個執行緒在迴圈中增加一個變數 while ，並執行固定時間。

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 定義了執行緒優先權所有可能值的集合。 執行緒優先順序指定了各執行緒相對於另一執行緒的相對優先權。

每個執行緒都有指定的優先順序。 執行時內建立的執行緒初始被分配 Normal 優先權，而執行時外建立的執行緒進入執行時會保留先前的優先權。 你可以透過存取執行 Priority 緒的屬性來取得並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。 用來決定執行緒執行順序的排程演算法會因作業系統而異。 作業系統也能動態調整執行緒優先順序，因為使用者介面的焦點在前景與背景間移動。

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作業系統排程前達到 Running 。

另請參閱

• Thread
• 排程執行緒