System.Threading.ThreadState Enumeration

Summary

Specifies the execution states of a Thread.

C# Syntax:

[Flags] [Serializable] public enum ThreadState

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 Thread.Start. Not all combinations of ThreadState values are valid; for example, a thread cannot be in both the Aborted and Unstarted states.

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

Action	ThreadState
A thread is created within the common language runtime.	Unstarted
A thread calls Thread.Start	Running
The thread starts running.	Running
The thread calls Thread.Sleep	WaitSleepJoin
The thread calls Monitor.Wait on another object.	WaitSleepJoin
The thread calls Thread.Join on another thread.	WaitSleepJoin
Another thread calls Thread.Interrupt	Running
Another thread calls Thread.Suspend	SuspendRequested
The thread responds to a Thread.Suspend request.	Suspended
Another thread calls Thread.Resume	Running
Another thread calls Thread.Abort	AbortRequested
The thread responds to a Thread.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 Monitor.Wait, and another thread calls Thread.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 Monitor.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 if a thread is running by using code such as ((threadState & (Stopped | Unstarted)) == 0 .

System.Threading Namespace | Thread | MSDN: managedunmanagedthreading

System.Threading.ThreadState Member List:

Public Fields

Aborted	The thread is in the Stopped state.
AbortRequested	The Thread.Abort method has been invoked on the thread, but the thread has not yet received the pending ThreadAbortException that will attempt to terminate it.
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.
Running	The thread has been started, it is not blocked, and there is no pending ThreadAbortException.
Stopped	The thread has stopped.
StopRequested	The thread is being requested to stop. This is for internal use only.
Suspended	The thread has been suspended.
SuspendRequested	The thread is being requested to suspend.
Unstarted	The Thread.Start method has not been invoked on the thread.
WaitSleepJoin	The thread is blocked as a result of a call to Monitor.Wait, Thread.Sleep, or Thread.Join.

Hierarchy:

• System.Object
• System.ValueType
• System.Enum
• System.Threading.ThreadState

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