ThreadStateException Class

ThreadStateException Class

[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]

The exception that is thrown when a Thread is in an invalid ThreadState for the method call.


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

public class ThreadStateException : SystemException

The ThreadStateException type exposes the following members.

Public methodThreadStateException()Initializes a new instance of the ThreadStateException class with default properties.
Public methodThreadStateException(String)Initializes a new instance of the ThreadStateException class with a specified error message.
Public methodThreadStateException(String, Exception)Initializes a new instance of the ThreadStateException class with a specified error message and a reference to the inner exception that is the cause of this exception.

Public propertyDataGets a collection of key/value pairs that provide additional user-defined information about the exception. (Inherited from Exception.)
Public propertyHelpLinkGets or sets a link to the help file associated with this exception. (Inherited from Exception.)
Public propertyHResultGets or sets HRESULT, a coded numerical value that is assigned to a specific exception. (Inherited from Exception.)
Public propertyInnerExceptionGets the Exception instance that caused the current exception. (Inherited from Exception.)
Public propertyMessageGets a message that describes the current exception. (Inherited from Exception.)
Public propertySourceGets or sets the name of the application or the object that causes the error. (Inherited from Exception.)
Public propertyStackTraceGets a string representation of the frames on the call stack at the time the current exception was thrown. (Inherited from Exception.)

Public methodEquals(Object)Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
Protected methodFinalizeAllows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
Public methodGetBaseExceptionWhen overridden in a derived class, returns the Exception that is the root cause of one or more subsequent exceptions. (Inherited from Exception.)
Public methodGetHashCodeServes as a hash function for a particular type. (Inherited from Object.)
Public methodGetTypeGets the runtime type of the current instance. (Inherited from Exception.)
Protected methodMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodToStringCreates and returns a string representation of the current exception. (Inherited from Exception.)

Once a thread is created, it is in at least one of the ThreadState states until it terminates. ThreadStateException is thrown by methods that cannot perform the requested operation due to the current state of a thread. For example, trying to restart a thread by calling Start on a thread that has terminated throws a ThreadStateException.

ThreadStateException uses the HRESULT COR_E_THREADSTATE, which has the value 0x80131520.

For a list of initial property values for an instance of ThreadStateException, see the ThreadStateException constructors.

The following example demonstrates an error that causes the system to throw a ThreadStateException. The example starts a thread and then attempts to start the thread again. It doesn't matter whether the thread is still running or has already terminated; it cannot be restarted, and a ThreadStateException is thrown.

using System;
using System.Threading;

class Example
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
      Thread myThread = new Thread(DoWork);

      outputBlock.Text += "Starting the thread.\n";

      outputBlock.Text += "Attempting to start the thread again.\n";
      catch(ThreadStateException e)
         outputBlock.Text += 
            String.Format("Caught ThreadStateException: {0}\n", e.Message);

   public static void DoWork()


/* This example produces the following output:

Starting the thread.
Attempting to start the thread again.
Caught ThreadStateException: Thread is running or terminated; it cannot restart.

Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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