SimpleDateFormat stores intermediate results in instance fields. So if one instance is used by two threads they can mess each other’s results. Looking at the source code reveals that there is a Calendar instance field, which is used by operations on DateFormat / SimpleDateFormat. For example parse(..) calls calendar.clear() initially and then calendar.add(..). If another … Read more
The lock statement is translated by C# 3.0 to the following: var temp = obj; Monitor.Enter(temp); try { // body } finally { Monitor.Exit(temp); } In C# 4.0 this has changed and it is now generated as follows: bool lockWasTaken = false; var temp = obj; try { Monitor.Enter(temp, ref lockWasTaken); // body } finally … Read more
Needed background on concurrency approaches: Different web servers implement different techniques for handling incoming HTTP requests in parallel. A pretty popular technique is using threads — that is, the web server will create/dedicate a single thread for each incoming request. The Apache HTTP web server supports multiple models for handling requests, one of which (called … Read more
What’s likely happening is that SignalData is indirectly changing the subscribers dictionary under the hood during the loop and leading to that message. You can verify this by changing foreach(Subscriber s in subscribers.Values) To foreach(Subscriber s in subscribers.Values.ToList()) If I’m right, the problem will disappear. Calling subscribers.Values.ToList() copies the values of subscribers.Values to a separate … Read more