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POIs this thread safe? Breakpoints get hit multiple times
 

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  1. POIs this thread safe? Breakpoints get hit multiple times
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    <p>I have the following code:</p> <pre><code>public class EmailJobQueue { private EmailJobQueue() { } private static readonly object JobsLocker = new object(); private static readonly Queue&lt;EmailJob&gt; Jobs = new Queue&lt;EmailJob&gt;(); private static readonly object ErroredIdsLocker = new object(); private static readonly List&lt;long&gt; ErroredIds = new List&lt;long&gt;(); public static EmailJob GetNextJob() { lock (JobsLocker) { lock (ErroredIdsLocker) { // If there are no jobs or they have all errored then get some new ones - if jobs have previously been skipped then this will re get them if (!Jobs.Any() || Jobs.All(j =&gt; ErroredIds.Contains(j.Id))) { var db = new DBDataContext(); foreach (var emailJob in db.Emailing_SelectSend(1)) { // Dont re add jobs that exist if (Jobs.All(j =&gt; j.Id != emailJob.Id) &amp;&amp; !ErroredIds.Contains(emailJob.Id)) { Jobs.Enqueue(new EmailJob(emailJob)); } } } while (Jobs.Any()) { var curJob = Jobs.Dequeue(); // Check the job has not previously errored - if they all have then eventually we will exit the loop if (!ErroredIds.Contains(curJob.Id)) return curJob; } return null; } } } public static void ReInsertErrored(long id) { lock (ErroredIdsLocker) { ErroredIds.Add(id); } } } </code></pre> <p>I then start 10 threads which do this:</p> <pre><code>var email = EmailJobQueue.GetNextJob(); if (email != null) { // Breakpoint here } </code></pre> <p>The thing is that if I put a breakpoint where the comment is and add one item to the queue then the breakpoint gets hit multiple times. Is this an issue with my code or a peculiarity with VS debugger?</p> <p>Thanks,</p> <p>Joe</p>
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    1. CODo you realize that this: `Jobs.All(j => ErrorIds.Contains(j.Id))` is checking every job against every error id, and if your lists get even moderately large it's going to be a serious performance problem? You probably want a way to improve your filtering.
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      1. USJim Mischel
    2. COWhat does `db.Emailing_SelectSend(1)` do?
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      1. USGreg
    3. COCome to think of it, this looks like a standard producer/consumer application. You should consider rewriting it so that you have one thread that populates a [BlockingCollection](http://msdn.microsoft.com/en-us/library/dd267312.aspx), and your worker threads read from that. Doing things that way will greatly simplify your program.
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