.net - How to lock on an integer in C#?

Question

Is there any way to lock on an integer in C#? Integers can not be used with lock because they are boxed (and lock only locks on references).

The scenario is as follows: I have a forum based website with a moderation feature. What I want to do is make sure that no more than one moderator can moderate a post at any given time. To achieve this, I want to lock on the ID of the post.

I've had a couple of ideas so far (e.g. using a dictionary<int, object>), but I'm looking for a better and cleaner way.

Any suggestions?

Answer 1

I like doing it like this

public class Synchronizer {
    private Dictionary<int, object> locks;
    private object myLock;

    public Synchronizer() {
        locks = new Dictionary<int, object>();
        myLock = new object();
    }

    public object this[int index] {
        get {
            lock (myLock) {
                object result;
                if (locks.TryGetValue(index, out result))
                    return result;

                result = new object();
                locks[index] = result;
                return result;
            }
        }
    }
}

Then, to lock on an int you simply (using the same synchronizer every time)

lock (sync[15]) { ... }

This class returns the same lock object when given the same index twice. When a new index comes, it create an object, returning it, and stores it in the dictionary for next times.

It can easily be changed to work generically with any struct or value type, or to be static so that the synchronizer object does not have to be passed around.