C# Data Structure Like Dictionary But Without A Value

Question

Is there any data structure in C# that is like a dictionary but that only has a key and doesn't have a value. I basically want a list of integers that I can quickly lookup and see if a certain value is in the list. Granted, for my current use, a List would not cause any performance problem, but it just doesn't seem to fit well with the intent of what my code is doing.

Answer 1

Yes, it's called a HashSet<T>, and available in version 3.5 of the .NET framework. If you use .NET version 2.0, you can use a Dictionary and set values to null.

Answer 2

or use a SortedList where values have to be unique

Answer 3

If 3.5 is not an option you could do something like Dictionary < int, int > and simply ignore the value. i've done this in 2.0 and i tend to set the value to the same as the key.

Answer 4

If you're not targeting .NET 3.5, Power Collections (open source) also provides a Set implementation.