Does anyone know if there is a good equivelent to Java's Set collection in C#.
It's one of the few things I miss from having moved to C#.
I am aware that you can have a "pretend" set using a Dictionary or Hashtable and only bothering to populate the keys. But it's not very elegant.
It's wierd every other way I turn in C# somone seems to have thought of a solution and built it into the framework, except for sets...
If you're using .NET 3.5, you can use HashSet<T>. It's true that .NET doesn't cater for sets as well as Java does though.
The Wintellect PowerCollections may help too.
I use Iesi.Collections http://www.codeproject.com/KB/recipes/sets.aspx
It's used in lot of OSS projects, I first came across it in NHibernate
Have a look at PowerCollections over at CodePlex. Apart from Set and OrderedSet it has a few other usefull collection types such as Deque, MultiDictionary, Bag, OrderedBag, OrderedDictionary and OrderedMultiDictionary.
For more collections, there is also the C5 Generic Collection Library.
You could implement your own workable set implementation in a couple of hours. I used this when I had to do it (sorry, I don't have the code handy): http://java.sun.com/j2se/1.4.2/docs/api/java/util/Set.html
I had this same question for .NET, but used via Powershell 1.0
HashSet would be great, but it is not available in 2.0, but then I found this site :
"a","b","b","c","a" | Select-Object -Unique
returns a b c
So while not answering the C# question, hope it may be useful to a PowerShell user.
You can apply set operations to any two IEnumerables using the LINQ extension methods, which sometimes is sufficient: IEnumerable extension methods.
I use a wrapper around a Dictionary<T, object>, storing nulls in the values. This gives O(1) add, lookup and remove on the keys, and to all intents and purposes acts like a set.