Thread.Interrupt Method

Definition

Interrupts a thread that is in the WaitSleepJoin thread state.

public void Interrupt ();
Exceptions

The caller does not have the appropriate SecurityPermission.

Examples

The following code example shows the behavior of a running thread when it is interrupted and subsequently gets blocked.

using namespace System;
using namespace System::Security::Permissions;
using namespace System::Threading;

ref class StayAwake
{
private:
   bool sleepSwitch;

public:

   property bool SleepSwitch 
   {
      void set( bool value )
      {
         sleepSwitch = value;
      }

   }
   StayAwake()
   {
      sleepSwitch = false;
   }

   void ThreadMethod()
   {
      Console::WriteLine( "newThread is executing ThreadMethod." );
      while (  !sleepSwitch )
      {
         
         // Use SpinWait instead of Sleep to demonstrate the 
         // effect of calling Interrupt on a running thread.
         Thread::SpinWait( 10000000 );
      }

      try
      {
         Console::WriteLine( "newThread going to sleep." );
         
         // When newThread goes to sleep, it is immediately 
         // woken up by a ThreadInterruptedException.
         Thread::Sleep( Timeout::Infinite );
      }
      catch ( ThreadInterruptedException^ /*e*/ ) 
      {
         Console::WriteLine( "newThread cannot go to sleep - "
         "interrupted by main thread." );
      }

   }

};

int main()
{
   StayAwake^ stayAwake = gcnew StayAwake;
   Thread^ newThread = gcnew Thread( gcnew ThreadStart( stayAwake, &StayAwake::ThreadMethod ) );
   newThread->Start();
   
   // The following line causes an exception to be thrown 
   // in ThreadMethod if newThread is currently blocked
   // or becomes blocked in the future.
   newThread->Interrupt();
   Console::WriteLine( "Main thread calls Interrupt on newThread." );
   
   // Then tell newThread to go to sleep.
   stayAwake->SleepSwitch = true;
   
   // Wait for newThread to end.
   newThread->Join();
}

using System;
using System.Security.Permissions;
using System.Threading;

class ThreadInterrupt
{
    static void Main()
    {
        StayAwake stayAwake = new StayAwake();
        Thread newThread = 
            new Thread(new ThreadStart(stayAwake.ThreadMethod));
        newThread.Start();

        // The following line causes an exception to be thrown 
        // in ThreadMethod if newThread is currently blocked
        // or becomes blocked in the future.
        newThread.Interrupt();
        Console.WriteLine("Main thread calls Interrupt on newThread.");

        // Tell newThread to go to sleep.
        stayAwake.SleepSwitch = true;

        // Wait for newThread to end.
        newThread.Join();
    }
}

class StayAwake
{
    bool sleepSwitch = false;

    public bool SleepSwitch
    {
        set{ sleepSwitch = value; }
    }

    public StayAwake(){}

    public void ThreadMethod()
    {
        Console.WriteLine("newThread is executing ThreadMethod.");
        while(!sleepSwitch)
        {
            // Use SpinWait instead of Sleep to demonstrate the 
            // effect of calling Interrupt on a running thread.
            Thread.SpinWait(10000000);
        }
        try
        {
            Console.WriteLine("newThread going to sleep.");

            // When newThread goes to sleep, it is immediately 
            // woken up by a ThreadInterruptedException.
            Thread.Sleep(Timeout.Infinite);
        }
        catch(ThreadInterruptedException e)
        {
            Console.WriteLine("newThread cannot go to sleep - " +
                "interrupted by main thread.");
        }
    }
}
Option Explicit
Option Strict

Imports System
Imports System.Security.Permissions
Imports System.Threading

Public Class ThreadInterrupt

    <MTAThread> _
    Shared Sub Main()
        Dim stayAwake As New StayAwake()
        Dim newThread As New Thread(AddressOf stayAwake.ThreadMethod)
        newThread.Start()

        ' The following line causes an exception to be thrown 
        ' in ThreadMethod if newThread is currently blocked
        ' or becomes blocked in the future.
        newThread.Interrupt()
        Console.WriteLine("Main thread calls Interrupt on newThread.")

        ' Tell newThread to go to sleep.
        stayAwake.SleepSwitch = True

        ' Wait for newThread to end.
        newThread.Join()
    End Sub

End Class

Public Class StayAwake

    Dim sleepSwitchValue As Boolean = False

    WriteOnly Property SleepSwitch As Boolean
        Set
            sleepSwitchValue = Value
        End Set
    End Property 

    Sub New()
    End Sub

    Sub ThreadMethod()
        Console.WriteLine("newThread is executing ThreadMethod.")
        While Not sleepSwitchValue

            ' Use SpinWait instead of Sleep to demonstrate the 
            ' effect of calling Interrupt on a running thread.
            Thread.SpinWait(10000000)
        End While
        Try
            Console.WriteLine("newThread going to sleep.")

            ' When newThread goes to sleep, it is immediately 
            ' woken up by a ThreadInterruptedException.
            Thread.Sleep(Timeout.Infinite)
        Catch ex As ThreadInterruptedException
            Console.WriteLine("newThread cannot go to " & _
                "sleep - interrupted by main thread.")
        End Try
    End Sub

End Class

Remarks

If this thread is not currently blocked in a wait, sleep, or join state, it will be interrupted when it next begins to block.

ThreadInterruptedException is thrown in the interrupted thread, but not until the thread blocks. If the thread never blocks, the exception is never thrown, and thus the thread might complete without ever being interrupted.