List.Sort() throws InvalidOperationException (instead of re-throw ThreadAbortException) while thread is being aborted

List.Sort() throws InvalidOperationException (instead of re-throw ThreadAbortException) while thread is being aborted by Andrzej P

Closed

as Won't Fix Help for as Won't Fix

Type:	Bug
ID:	605536
Opened:	9/27/2010 4:27:15 AM
Access Restriction:	Public

Workaround(s)

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User(s) can reproduce this bug

List.Sort() throws InvalidOperationException (instead of re-throw ThreadAbortException) when thread is being aborted and ThreadAbortException occurs in Comparer while sorting.

Details (expand)

Visual Studio 2010

Build and run following Hello Word Console application:

using System;
using System.Collections.Generic;
using System.Threading;

namespace HelloWordSortIssue
{
    class Item : IComparable<Item>
    {
        ManualResetEvent threadSortingStartedEvent;
        public int ID { get; private set; }

        public Item(int id, ManualResetEvent threadSortingStartedEvent)
        {
            this.ID = id;
            this.threadSortingStartedEvent = threadSortingStartedEvent;
        }

        public int CompareTo(Item other)
        {
            threadSortingStartedEvent.Set();
            System.Threading.Thread.Sleep(1); // ThreadAbortException will be thrown here
            if (other == null)
                return 1;
            return this.ID.CompareTo(other.ID);
        }
    }

    class Program
    {
        ManualResetEvent threadSortingStartedEvent = new ManualResetEvent(false);

        static void Main(string[] args)
        {
            new Program().Main();
        }

        void Main()
        {
            Thread thread = new Thread(this.ThreadProc);
            thread.Start();
            threadSortingStartedEvent.WaitOne(); // wait to start sorting
            thread.Abort();
            thread.Join();
        }

        void ThreadProc()
        {
            try
            {
                Random rand = new Random((int)DateTime.Now.Ticks);
                List<Item> items = new List<Item>();
                for (int i = 0; i < 1000; i++)
                    items.Add(new Item(rand.Next(), this.threadSortingStartedEvent));

                // List.Sort() will throw here System.InvalidOperationException instead of ThreadAbortException
                items.Sort();
            }
            catch (ThreadAbortException)
            {
                Console.WriteLine("Thread aborted.");
            }
            catch (ThreadInterruptedException)
            {
                Console.WriteLine("Thread interrupted.");
            }
            catch (Exception ex)
            {
                Console.WriteLine("Error in background thread: {0}", ex);
            }
        }
    }
}

English

Windows 7

Polish

InvalidOperationException thrown by List.Sort

ThreadAbortException re-thrown by List.Sort

0 attachments

Thanks for reporting this issue. I wanted to let you know that we have looked into this and have decided not to change the current behavior. If a Comparer throws an unexpected exception when List<T>.Sort is used, it throws InvalidOperationException and set the inner exception to the unexpected error (in this case ThreadAbortException). This behavior is by design. Also note that it is generally a bad idea to rely on Thread.Abort. Some more info is available here: http://www.interact-sw.co.uk/iangblog/2004/11/12/cancellation

Therefore, I've gone ahead and resolved this as Won't Fix. Please let me know if you have any questions or concerns at justinv at microsoft dot com.

Regards,

Justin Van Patten
CLR Base Class Libraries