ThreadPriority 枚举

定义

命名空间:

System.Threading

程序集:

netstandard.dll, System.Threading.Thread.dll

Source:

ThreadPriority.cs

指定 Thread的计划优先级。

public enum class ThreadPriority

public enum ThreadPriority

type ThreadPriority = 

Public Enum ThreadPriority

继承

Object

ValueType

Enum

ThreadPriority

字段

名称	值	说明
Lowest	0	Thread可以在具有任何其他优先级的线程之后进行计划。
BelowNormal	1	Thread可以在具有优先级的Normal线程之后和优先级的Lowest线程之前进行计划。
Normal	2	Thread可以在具有优先级的AboveNormal线程之后和优先级的BelowNormal线程之前进行计划。 默认情况下，线程具有 Normal 优先级。
AboveNormal	3	Thread可以在具有优先级的Highest线程之后和优先级的Normal线程之前进行计划。
Highest	4	Thread可以在具有任何其他优先级的线程之前计划该线程。

示例

下面的代码示例显示了更改线程优先级的结果。 创建三个线程，一个线程的优先级设置为 BelowNormal，第二个线程的优先级设置为 AboveNormal。 每个线程在循环中递增一个 while 变量，并在一定时间内运行。

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

注解

ThreadPriority 定义线程优先级的所有可能值集。 线程优先级指定一个线程相对于另一个线程的相对优先级。

每个线程都有一个分配的优先级。 在运行时中创建的线程最初分配 Normal 优先级，而在运行时外部创建的线程在进入运行时时会保留其以前的优先级。 可以通过访问线程属性来获取和设置线程 Priority 的优先级。

线程根据优先级被排入执行计划。 用于确定线程执行顺序的计划算法因每个操作系统而异。 操作系统还可以动态调整线程优先级，因为用户界面的焦点在前台和后台之间移动。

线程的优先级不会影响线程的状态;线程的状态必须是 Running 操作系统可以计划它之前。

另请参阅

• Thread
• 计划线程