The reason why there is no such a data structure is that all collections have lookup operation time of O(n). These are IndexOf, Remove(element) etc. They all enumerate through all elements and checking them for equality. Only hash tables have lookup time of O(1). In concurrent scenario O(n) lookup time would lead to very long … Read more
Let me ask you this: how realistic is it that you’d have an application which is constantly adding to a collection and never reading from it? What’s the use of such a collection? (This is not a purely rhetorical question. I could imagine there being uses where, e.g., you only read from the collection on … Read more
(I know this is an old post, thought I’d add a little something). Like others have said: yes, you need to add them one by one. In my case, I added a small extension method to make things a bit cleaner, but under the hood it does the same thing: public static void AddRange<T>(this ConcurrentBag<T> … Read more
This looks like an ok use of ConcurrentBag. The thread local variables are members of the bag, and will become eligible for garbage collection at the same time the bag is (clearing the contents won’t release them). You are right that a simple List with a lock would suffice for your case. If the work … Read more
The SynchronizedCollection<T> class was introduced first in .NET 2.0 to provide a thread-safe collection class. It does this via locking so that you essentially have a List<T> where every access is wrapped in a lock statement. The System.Collections.Concurrent namespace is much newer. It wasn’t introduced until .NET 4.0 and it includes a substantially improved and … Read more
You need to pass a Func which returns the value to be stored in the dictionary in case of an update. I guess in your case (since you don’t distinguish between add and update) this would be: var sessionId = a.Session.SessionID.ToString(); userDic.AddOrUpdate( authUser.UserId, sessionId, (key, oldValue) => sessionId); I.e. the Func always returns the sessionId, … Read more