Specifies the scheduling priority of a Thread.
Namespace:
System.Threading
Assembly:
mscorlib (in mscorlib.dll)
Visual Basic (Declaration)
<SerializableAttribute> _
<ComVisibleAttribute(True)> _
Public Enumeration ThreadPriority
Dim instance As ThreadPriority
[SerializableAttribute]
[ComVisibleAttribute(true)]
public enum ThreadPriority
[SerializableAttribute]
[ComVisibleAttribute(true)]
public enum class ThreadPriority
public enum ThreadPriority
| Member name | Description |
|---|
.gif) .gif) | Lowest | The Thread can be scheduled after threads with any other priority. |
.gif) .gif) | BelowNormal | The Thread can be scheduled after threads with Normal priority and before those with Lowest priority. |
.gif) .gif) | Normal | The Thread can be scheduled after threads with AboveNormal priority and before those with BelowNormal priority. Threads have Normal priority by default. |
.gif) .gif) | AboveNormal | The Thread can be scheduled after threads with Highest priority and before those with Normal priority. |
.gif) .gif) | Highest | The Thread can be scheduled before threads with any other priority. |
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
using System;
using System.Threading;
class Test
{
static void Main()
{
PriorityTest priorityTest = new PriorityTest();
ThreadStart startDelegate =
new ThreadStart(priorityTest.ThreadMethod);
Thread threadOne = new Thread(startDelegate);
threadOne.Name = "ThreadOne";
Thread threadTwo = new Thread(startDelegate);
threadTwo.Name = "ThreadTwo";
threadTwo.Priority = ThreadPriority.BelowNormal;
threadOne.Start();
threadTwo.Start();
// Allow counting for 10 seconds.
Thread.Sleep(10000);
priorityTest.LoopSwitch = false;
}
}
class PriorityTest
{
bool loopSwitch;
public PriorityTest()
{
loopSwitch = true;
}
public bool LoopSwitch
{
set{ loopSwitch = value; }
}
public void ThreadMethod()
{
long threadCount = 0;
while(loopSwitch)
{
threadCount++;
}
Console.WriteLine("{0} with {1,11} priority " +
"has a count = {2,13}", Thread.CurrentThread.Name,
Thread.CurrentThread.Priority.ToString(),
threadCount.ToString("N0"));
}
}
using namespace System;
using namespace System::Threading;
ref class PriorityTest
{
private:
bool loopSwitch;
public:
PriorityTest()
{
loopSwitch = true;
}
property bool LoopSwitch
{
void set( bool value )
{
loopSwitch = value;
}
}
void ThreadMethod()
{
__int64 threadCount = 0;
while ( loopSwitch )
{
threadCount++;
}
Console::WriteLine( "{0} with {1,11} priority "
"has a count = {2,13}", Thread::CurrentThread->Name, Thread::CurrentThread->Priority.ToString(), threadCount.ToString( "N0" ) );
}
};
int main()
{
PriorityTest^ priorityTest = gcnew PriorityTest;
ThreadStart^ startDelegate = gcnew ThreadStart( priorityTest, &PriorityTest::ThreadMethod );
Thread^ threadOne = gcnew Thread( startDelegate );
threadOne->Name = "ThreadOne";
Thread^ threadTwo = gcnew Thread( startDelegate );
threadTwo->Name = "ThreadTwo";
threadTwo->Priority = ThreadPriority::BelowNormal;
threadOne->Start();
threadTwo->Start();
// Allow counting for 10 seconds.
Thread::Sleep( 10000 );
priorityTest->LoopSwitch = false;
}
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
.NET Framework
Supported in: 3.5, 3.0, 2.0, 1.1, 1.0
.NET Compact Framework
Supported in: 3.5, 2.0, 1.0
XNA Framework
Supported in: 3.0, 2.0, 1.0
Reference
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