Getting unique items from a list [duplicate]

What is the fastest / most efficient way of getting all the distinct items from a list?

I have a List<string> that possibly has multiple repeating items in it and only want the unique values within the list.

Solution 1:

You can use the Distinct method to return an IEnumerable<T> of distinct items:

var uniqueItems = yourList.Distinct();

And if you need the sequence of unique items returned as a List<T>, you can add a call to ToList:

var uniqueItemsList = yourList.Distinct().ToList();

Solution 2:

Use a HashSet<T>. For example:

var items = "A B A D A C".Split(' ');
var unique_items = new HashSet<string>(items);
foreach (string s in unique_items)
    Console.WriteLine(s);

prints

A
B
D
C

Solution 3:

You can use Distinct extension method from LINQ