MultiMap implementation

I'm writing a simple IDictionary abstraction in C# that wraps a Dictionary<K, ICollection<V>>. Basically, it maps multiple values to one key. I can't decide whether to remove a key and its empty list when the last item in a values list is removed, or leave it (to avoid instantiating a new collection if the key is reused) and do checks on a key's values' Count when determining whether a key exists.


I would remove the collections so that your MultiMap has consistent behavior. If I used your MultiMap I would be very surprised (and unhappy) to find that a missing key behaves differently depending on whether a key was previously in the MultiMap or not.

Does Clear() remove the the Collections?

You may also create an unintended memory leak if you do not remove the collections. A developer may add many items, then remove them. Memory usage (after GC) should return to the same amount as before those items were added.

I would not worry about the cost of creating Collections. I would worry about the contract you create for your MultiMap. If after profiling your application you find that to be a concerned, you could modify or create a special MultiMap for that behavior. Don't fall into the trap of premature optimization.

Need Your Help

Sharing code between OS X (Objective-C) and iOS (Swift)

ios objective-c osx cocoa swift

I have a Mac app written in Objective-C. Now I want to make a iOS version of it, written in Swift.

About UNIX Resources Network

Original, collect and organize Developers related documents, information and materials, contains jQuery, Html, CSS, MySQL, .NET, ASP.NET, SQL, objective-c, iPhone, Ruby on Rails, C, SQL Server, Ruby, Arrays, Regex, ASP.NET MVC, WPF, XML, Ajax, DataBase, and so on.