ThreadState Enumeration (System.Threading)

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.NET Framework Class Library

ThreadState Enumeration

Updated: March 2011

Specifies the execution states of a Thread.

This enumeration has a FlagsAttribute attribute that allows a bitwise combination of its member values.

Namespace: System.Threading
Assembly: mscorlib (in mscorlib.dll)

Syntax

Visual Basic

<SerializableAttribute> _
<ComVisibleAttribute(True)> _
<FlagsAttribute> _
Public Enumeration ThreadState

[SerializableAttribute]
[ComVisibleAttribute(true)]
[FlagsAttribute]
public enum ThreadState

Visual C++

[SerializableAttribute]
[ComVisibleAttribute(true)]
[FlagsAttribute]
public enum class ThreadState

[<SerializableAttribute>]
[<ComVisibleAttribute(true)>]
[<FlagsAttribute>]
type ThreadState

Members

	Member name	Description
	Running	The thread has been started, it is not blocked, and there is no pending ThreadAbortException.
	StopRequested	The thread is being requested to stop. This is for internal use only.
	SuspendRequested	The thread is being requested to suspend.
	Background	The thread is being executed as a background thread, as opposed to a foreground thread. This state is controlled by setting the Thread.IsBackground property.
	Unstarted	The Thread.Start method has not been invoked on the thread.
	Stopped	The thread has stopped.
	WaitSleepJoin	The thread is blocked. This could be the result of calling Thread.Sleep or Thread.Join, of requesting a lock — for example, by calling Monitor.Enter or Monitor.Wait — or of waiting on a thread synchronization object such as ManualResetEvent.
	Suspended	The thread has been suspended.
	AbortRequested	The Thread.Abort method has been invoked on the thread, but the thread has not yet received the pending System.Threading.ThreadAbortException that will attempt to terminate it.
	Aborted	The thread state includes AbortRequested and the thread is now dead, but its state has not yet changed to Stopped.

Remarks

The ThreadState enumeration is of interest only in a few debugging scenarios. Your code should never use the thread state to synchronize the activities of threads.

ThreadState defines a set of all possible execution states for threads. Once a thread is created, it is in at least one of the states until it terminates. Threads created within the common language runtime are initially in the Unstarted state, while external threads that come into the runtime are already in the Running state. An Unstarted thread is transitioned into the Running state by calling Start. Not all combinations of ThreadState values are valid; for example, a thread cannot be in both the Aborted and Unstarted states.

Note
There are two thread state enumerations, System.Threading.ThreadState and System.Diagnostics.ThreadState.

The following table shows the actions that cause a change of state.

Action	ThreadState
A thread is created within the common language runtime.	Unstarted
Another thread calls the Thread.Start method on the new thread, and the call returns. Note The Start method does not return until the new thread has started running. There is no way to know at what point the new thread will start running during the call to Start.	Running
The thread calls Sleep.	WaitSleepJoin
The thread calls Wait on another object.	WaitSleepJoin
The thread calls Join on another thread.	WaitSleepJoin
Another thread calls Interrupt.	Running
Another thread calls Suspend.	SuspendRequested
The thread responds to a Suspend request.	Suspended
Another thread calls Resume.	Running
Another thread calls Abort.	AbortRequested
The thread responds to a Abort request.	Stopped
The thread is terminated.	Stopped

In addition to the states noted above, there is also the Background state, which indicates whether the thread is running in the background or foreground.

A thread can be in more than one state at a given time. For example, if a thread is blocked on a call to Wait, and another thread calls Abort on the blocked thread, the blocked thread will be in both the WaitSleepJoin and the AbortRequested states at the same time. In this case, as soon as the thread returns from the call to Wait or is interrupted, it will receive the ThreadAbortException to begin aborting.

The Thread.ThreadState property of a thread provides the current state of a thread. Applications must use a bitmask to determine whether a thread is running. Since the value for Running is zero (0), test whether a thread is running by using C# code such as (myThread.ThreadState & (ThreadState.Stopped | ThreadState.Unstarted)) == 0 or Visual Basic code such as (myThread.ThreadState And (ThreadState.Stopped Or ThreadState.Unstarted)) = 0.

Version Information

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Platforms

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Reference

System.Threading Namespace

Thread

Other Resources

Managed Thread States

Managed and Unmanaged Threading

Change History

Date	History	Reason
March 2011	Clarified the relationship between the Thread.Start method and the Running state, and emphasized that the ThreadState enumeration should not be used to synchronize the activities of threads.	Content bug fix.

Date

History

Reason

March 2011

Clarified the relationship between the Thread.Start method and the Running state, and emphasized that the ThreadState enumeration should not be used to synchronize the activities of threads.

Content bug fix.