Ayende @ Rahien

Chris Smith commented on I love ConcurrentDictionary!

Fri, 26 Mar 2010 12:12:26 GMT

This looks something like Redis ( [http://code.google.com/p/redis/](http://code.google.com/p/redis/) ), which I just happen to be building some .Net client software for here: [http://code.google.com/p/redisdotnet/](http://code.google.com/p/redisdotnet/) That allows a vast number of atomic thread-safe actions to be done on a remote dictionary.

tobi commented on I love ConcurrentDictionary!

Mon, 22 Mar 2010 13:43:49 GMT

Although it is beside your point you use a single dictionary with a tuple as the key.

configurator commented on I love ConcurrentDictionary!

Mon, 22 Mar 2010 12:25:17 GMT

Shouldn't you use some concurrent datatype for the list as well?

Robert Byrne commented on I love ConcurrentDictionary!

Mon, 22 Mar 2010 11:30:24 GMT

Yea some of the first extension methods I wrote were to deal with dictionaries. If theres nothing special about the way you construct the value, you can simplify slightly: public static TValue GetOrAddDefaultValue(this IDictionary dictionary, TKey key) { if (dictionary == null) return default(TValue); TValue value = default(TValue); bool exists = dictionary.TryGetValue(key, out value); if (!exists) { if (typeof(TValue).IsValueType) { dictionary[key] = value; } else { value = Activator.CreateInstance(); dictionary[key] = value; } } return value; }

Paul Hatcher commented on I love ConcurrentDictionary!

Mon, 22 Mar 2010 11:24:01 GMT

You'd need some form of locking to make it thread safe, e.g. TValue value; lock (collection) { if (!collection.TryGetValue(key, out value)) collection.Add(key, value = generator(key)); } return value; And of course this doesn't preclude someone bypassing the lock by directly doing collection.Add

Torkel commented on I love ConcurrentDictionary!

Mon, 22 Mar 2010 11:19:02 GMT

That is a pretty useful function! Dam, why did I not think of writing one like that. I do have a similar one I use for caches. For example: return cache.GetWithAdd("admembers", () => GetADMemberListRemote());

Tommy Carlier commented on I love ConcurrentDictionary!

Mon, 22 Mar 2010 10:33:36 GMT

Your commenting system apparently doesn't escape less-than and greater-than. Second attempt: static TValue GetOrAdd(this IDictionary collection, TKey key, Func generator) { TValue value; if (!collection.TryGetValue(key, out value)) collection.Add(key, value = generator(key)); return value; }

Tommy Carlier commented on I love ConcurrentDictionary!

Mon, 22 Mar 2010 10:31:43 GMT

That's awesome. You could do this with regular dictionaries, by adding an extension method to IDictionary , like this: static TValue GetOrAdd (this IDictionary collection, TKey key, Func generator) { TValue value; if (!collection.TryGetValue(key, out value)) collection.Add(key, value = generator(key)); return value; }