Question

Here is my code:

var messageHandlers = new Dictionary<Type, Action<T>>();

public static void Subscribe(Action<T> message)
{
    if (messageHandlers.ContainsKey(typeof(T)))
    {
        messageHandlers[typeof(T)] += message;
    }
    else
    {
        messageHandlers.Add(typeof(T), message);
    }
}

Is there any way to make this a one liner?

Answer 1

You can’t make it a one-liner, but you can make it faster:

Action<T> current;
messageHandlers.TryGetValue(typeof(T), out current);
messageHandlers[typeof(T)] = current + message;

The Dictionary<> indexer will add non-existent keys.

If you switch to a ConcurrentDictionary<>, you can make it a one-liner:

dict.AddOrUpdate(typeof(T), message, (key, current) => current + message);