C#idiomatic C#
destroying-threadsstandard/threading

Async and concurrency

Destroy threads

Know your options when you need to destroy a thread in .NET, such as cooperative cancellation or the Thread.Abort method. Learn to handle ThreadAbortException.

  • page standard/threading/destroying-threads
  • updated 03/13/2026

To terminate the execution of the thread, you usually use the cooperative cancellation model. However, sometimes it's not possible to stop a thread cooperatively, because it runs third-party code not designed for cooperative cancellation. In .NET Framework apps, you can use the System.Threading.Thread.Abort method to terminate a managed thread forcibly. When you call System.Threading.Thread.Abort, the Common Language Runtime throws a System.Threading.ThreadAbortException in the target thread, which the target thread can catch. (However, the .NET Framework runtime always automatically rethrows the exception after the catch block.) For more information, see System.Threading.Thread.Abort.

The System.Threading.Thread.Abort method throws a System.PlatformNotSupportedException at runtime in .NET Core and .NET 5 and later versions. Starting in .NET 5, it's also marked obsolete (SYSLIB0006), so calling it generates a compile-time warning. If you need to terminate the execution of third-party code forcibly in modern .NET implementations, run it in the separate process and use System.Diagnostics.Process.Kill.

Once a thread is aborted, it cannot be restarted.

The System.Threading.Thread.Abort method does not cause the thread to abort immediately, because the target thread can catch the System.Threading.ThreadAbortException and execute arbitrary amounts of code in a finally block. You can call System.Threading.Thread.Join if you need to wait until the thread has ended. System.Threading.Thread.Join is a blocking call that does not return until the thread has actually stopped executing or an optional timeout interval has elapsed. The aborted thread could call the System.Threading.Thread.ResetAbort method or perform unbounded processing in a finally block, so if you do not specify a timeout, the wait is not guaranteed to end.

Threads that are waiting on a call to the System.Threading.Thread.Join method can be interrupted by other threads that call System.Threading.Thread.Interrupt.

Handling ThreadAbortException

If you expect your thread to be aborted, either as a result of calling System.Threading.Thread.Abort from your own code or as a result of unloading an application domain in which the thread is running (System.AppDomain.Unload uses System.Threading.Thread.Abort to terminate threads), your thread must handle the System.Threading.ThreadAbortException and perform any final processing in a finally clause, as shown in the following code.

vb
Try
    ' Code that is executing when the thread is aborted.
Catch ex As ThreadAbortException
    ' Clean-up code can go here.
    ' If there is no Finally clause, ThreadAbortException is
    ' re-thrown by the system at the end of the Catch clause.
Finally
    ' Clean-up code can go here.
End Try
' Do not put clean-up code here, because the exception
' is rethrown at the end of the Finally clause.
csharp
try
{
    // Code that is executing when the thread is aborted.
}
catch (ThreadAbortException ex)
{
    // Clean-up code can go here.
    // If there is no Finally clause, ThreadAbortException is
    // re-thrown by the system at the end of the Catch clause.
}
// Do not put clean-up code here, because the exception
// is rethrown at the end of the Finally clause.

Your clean-up code must be in the catch clause or the finally clause, because a System.Threading.ThreadAbortException is rethrown by the system at the end of the finally clause, or at the end of the catch clause if there is no finally clause.

You can prevent the system from rethrowing the exception by calling the System.Threading.Thread.ResetAbort method. However, you should do this only if your own code caused the System.Threading.ThreadAbortException.

See also