Article
11/18/2011

ThreadStateException Class

Microsoft Silverlight will reach end of support after October 2021. Learn more.

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

Inheritance Hierarchy

System.Object
  System.Exception
    System.SystemException
      System.Threading.ThreadStateException

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

Syntax

'Declaration
<ComVisibleAttribute(True)> _
Public Class ThreadStateException _
    Inherits SystemException

[ComVisibleAttribute(true)]
public class ThreadStateException : SystemException

The ThreadStateException type exposes the following members.

Constructors

	Name	Description
	ThreadStateException()	Initializes a new instance of the ThreadStateException class with default properties.
	ThreadStateException(String)	Initializes a new instance of the ThreadStateException class with a specified error message.
	ThreadStateException(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.

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Properties

	Name	Description
	Data	Gets a collection of key/value pairs that provide additional user-defined information about the exception. (Inherited from Exception.)
	HResult	Gets or sets HRESULT, a coded numerical value that is assigned to a specific exception. (Inherited from Exception.)
	InnerException	Gets the Exception instance that caused the current exception. (Inherited from Exception.)
	Message	Gets a message that describes the current exception. (Inherited from Exception.)
	StackTrace	Gets a string representation of the frames on the call stack at the time the current exception was thrown. (Inherited from Exception.)

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Methods

	Name	Description
	Equals(Object)	Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
	Finalize	Allows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
	GetBaseException	When overridden in a derived class, returns the Exception that is the root cause of one or more subsequent exceptions. (Inherited from Exception.)
	GetHashCode	Serves as a hash function for a particular type. (Inherited from Object.)
	GetType	Gets the runtime type of the current instance. (Inherited from Exception.)
	MemberwiseClone	Creates a shallow copy of the current Object. (Inherited from Object.)
	ToString	Creates and returns a string representation of the current exception. (Inherited from Exception.)

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Remarks

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.

Examples

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.

Note:
To run this example, see Building Examples That Use a Demo Method and a TextBlock Control.

Imports System.Threading

Class Example

   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)

      Dim myThread As New Thread(AddressOf DoWork)

      outputBlock.Text &= "Starting the thread." & vbCrLf
      myThread.Start()

      outputBlock.Text &= "Attempting to start the thread again." & vbCrLf
      Try
         myThread.Start()
      Catch e As ThreadStateException
         outputBlock.Text &= _
            String.Format("Caught ThreadStateException: {0}", e.Message) & vbCrLf
      End Try
   End Sub 

   Public Shared Sub DoWork()
   End Sub 

End Class 

' 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.

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";
      myThread.Start();

      outputBlock.Text += "Attempting to start the thread again.\n";
      try
      {
         myThread.Start();
      }
      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.
 */

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

Thread Safety

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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