Lock only on an Id

Question

I have a method which needs to run exclusivley run a block of code, but I want to add this restriction only if it is really required. Depending on an Id value (an Int32) I w

Answer 1

I used the following approach. Do not check the original ID, but get small hash-code of int type to get the existing object for lock. The count of lockers depends on your situation - the more locker counter, the less the probability of collision.

class ThreadLocker
{
    const int DEFAULT_LOCKERS_COUNTER = 997;
    int lockersCount;
    object[] lockers;

    public ThreadLocker(int MaxLockersCount)
    {
        if (MaxLockersCount < 1) throw new ArgumentOutOfRangeException("MaxLockersCount", MaxLockersCount, "Counter cannot be less, that 1");
        lockersCount = MaxLockersCount;
        lockers = Enumerable.Range(0, lockersCount).Select(_ => new object()).ToArray();
    }
    public ThreadLocker() : this(DEFAULT_LOCKERS_COUNTER) { }

    public object GetLocker(int ObjectID)
    {
        var idx = (ObjectID % lockersCount + lockersCount) % lockersCount;
        return lockers[idx];
    }
    public object GetLocker(string ObjectID)
    {
        var hash = ObjectID.GetHashCode();
        return GetLocker(hash);
    }
    public object GetLocker(Guid ObjectID)
    {
        var hash = ObjectID.GetHashCode();
        return GetLocker(hash);
    }
}

Usage:

partial class Program
{
    static ThreadLocker locker = new ThreadLocker();
    static void Main(string[] args)
    {
        var id = 10;
        lock(locker.GetLocker(id))
        {

        }
    }
}

Of cource, you can use any hash-code functions to get the corresponded array index.