ThreadState ThreadState ThreadState ThreadState Enum

Definition

Specifies the execution states of a Thread.

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

public enum class ThreadState
[System.Flags]
[System.Runtime.InteropServices.ComVisible(true)]
[Serializable]
public enum ThreadState
type ThreadState = 
Public Enum ThreadState
Inheritance
Attributes
FlagsAttribute ComVisibleAttribute SerializableAttribute

Fields

Aborted Aborted Aborted Aborted 256

The thread state includes AbortRequested and the thread is now dead, but its state has not yet changed to Stopped.

AbortRequested AbortRequested AbortRequested AbortRequested 128

The Abort(Object) method has been invoked on the thread, but the thread has not yet received the pending ThreadAbortException that will attempt to terminate it.

Background Background Background Background 4

The thread is being executed as a background thread, as opposed to a foreground thread. This state is controlled by setting the IsBackground property.

Running Running Running Running 0

The thread has been started, it is not blocked, and there is no pending ThreadAbortException.

Stopped Stopped Stopped Stopped 16

The thread has stopped.

StopRequested StopRequested StopRequested StopRequested 1

The thread is being requested to stop. This is for internal use only.

Suspended Suspended Suspended Suspended 64

The thread has been suspended.

SuspendRequested SuspendRequested SuspendRequested SuspendRequested 2

The thread is being requested to suspend.

Unstarted Unstarted Unstarted Unstarted 8

The Start() method has not been invoked on the thread.

WaitSleepJoin WaitSleepJoin WaitSleepJoin WaitSleepJoin 32

The thread is blocked. This could be the result of calling Sleep(Int32) or Join(), of requesting a lock — for example, by calling Enter(Object) or Wait(Object, Int32, Boolean) — or of waiting on a thread synchronization object such as ManualResetEvent.

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.

Important

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.

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
A 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.

Applies to

See Also