# c# - when - Is there a “Set” data structure in.Net?

## struct vs class c# (4)

`HashSet<T>`

is about the closest you'll get, I think.

Ideally, I'm looking for a templated logical Set class. It would have all of the standard set operations such as Union, Intersection, Etc., and collapse duplicated items.

I ended up creating my own set class based on the C# Dictionary<>- just using the Keys.

Have you checked out the HashSet in 3.5?

I don't think c# has anything built in, but I know there are a couple of implementations floating around on the net. There are also some good articles around on this sort of thing:

This is part 6 of a series on efficiently representing data structure. This part focuses on representing sets in C#.

An implementation of a set collection

An implementation of a set class

Yet another implementation of a set class

And finally...

I've actually used this library myself as the basis of a set implementation that I did a year or so ago.

No, there is not one natively in the framework. There is an open source implementation that most projects use, (i.e. nHibernate) called Iesi.Collections. Here's a CodeProject article about it: