ThreadPriority Enumeration
Assembly: mscorlib (in mscorlib.dll)
'Declaration <SerializableAttribute> _ <ComVisibleAttribute(True)> _ Public Enumeration ThreadPriority 'Usage Dim instance As ThreadPriority
/** @attribute SerializableAttribute() */ /** @attribute ComVisibleAttribute(true) */ public enum ThreadPriority
SerializableAttribute ComVisibleAttribute(true) public enum ThreadPriority
| Member name | Description | |
|---|---|---|
![]() | AboveNormal | The Thread can be scheduled after threads with Highest priority and before those with Normal priority. |
![]() | BelowNormal | The Thread can be scheduled after threads with Normal priority and before those with Lowest priority. |
![]() | Highest | The Thread can be scheduled before threads with any other priority. |
![]() | Lowest | The Thread can be scheduled after threads with any other priority. |
![]() | Normal | The Thread can be scheduled after threads with AboveNormal priority and before those with BelowNormal priority. Threads have Normal priority by default. |
ThreadPriority defines the set of all possible values for a thread priority. Thread priorities specify the relative priority of one thread versus another.
Every thread has an assigned priority. Threads created within the runtime are initially assigned the Normal priority, while threads created outside the runtime retain their previous priority when they enter the runtime. You can get and set the priority of a thread by accessing its Priority property.
Threads are scheduled for execution based on their priority. The scheduling algorithm used to determine the order of thread execution varies with each operating system. The operating system can also adjust the thread priority dynamically as the user interface's focus is moved between the foreground and the background.
The priority of a thread does not affect the thread's state; the state of the thread must be Running before the operating system can schedule it.
The following code example shows the result of changing the priority of a thread. Two threads are created and the priority of one thread is set to BelowNormal. Both threads increment a variable in a while loop and run for a set time.
Option Explicit Option Strict Imports System Imports System.Threading Public Class Test <MTAThread> _ Shared Sub Main() Dim priorityTest As New PriorityTest() Dim threadOne As Thread = _ New Thread(AddressOf priorityTest.ThreadMethod) threadOne.Name = "ThreadOne" Dim threadTwo As Thread = _ New Thread(AddressOf priorityTest.ThreadMethod) threadTwo.Name = "ThreadTwo" threadTwo.Priority = ThreadPriority.BelowNormal threadOne.Start() threadTwo.Start() ' Allow counting for 10 seconds. Thread.Sleep(10000) priorityTest.LoopSwitch = False End Sub End Class Public Class PriorityTest Dim loopSwitchValue As Boolean Sub New() loopSwitchValue = True End Sub WriteOnly Property LoopSwitch As Boolean Set loopSwitchValue = Value End Set End Property Sub ThreadMethod() Dim threadCount As Long = 0 While loopSwitchValue threadCount += 1 End While Console.WriteLine("{0} with {1,11} priority " & _ "has a count = {2,13}", Thread.CurrentThread.Name, _ Thread.CurrentThread.Priority.ToString(), _ threadCount.ToString("N0")) End Sub End Class
import System.*;
import System.Threading.*;
import System.Threading.Thread;
class Test
{
public static void main(String[] args)
{
PriorityTest priorityTest = new PriorityTest();
ThreadStart startDelegate = new ThreadStart(priorityTest.ThreadMethod);
Thread threadOne = new Thread(startDelegate);
threadOne.set_Name("ThreadOne");
Thread threadTwo = new Thread(startDelegate);
threadTwo.set_Name("ThreadTwo");
threadTwo.set_Priority(ThreadPriority.BelowNormal);
threadOne.Start();
threadTwo.Start();
// Allow counting for 10 seconds.
Thread.Sleep(10000);
priorityTest.set_LoopSwitch(false);
} //main
} //Test
class PriorityTest
{
private boolean loopSwitch;
public PriorityTest()
{
loopSwitch = true;
} //PriorityTest
/** @property
*/
public void set_LoopSwitch(boolean value)
{
loopSwitch = value;
} //set_LoopSwitch
public void ThreadMethod()
{
long threadCount = 0;
while (loopSwitch) {
threadCount++;
}
Console.WriteLine("{0} with {1,11} priority " + "has a count = {2,13}",
Thread.get_CurrentThread().get_Name(),
Thread.get_CurrentThread().get_Priority().toString(),
((System.Int32)threadCount).ToString("N0"));
} //ThreadMethod
} //PriorityTest
Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.
Reference
System.Threading NamespaceThread Class
Other Resources
Scheduling ThreadsManaged and Unmanaged Threading
