Use the Distinct
method in LINQ.
See http://msdn.microsoft.com/en-us/library/bb348436.aspx
List ages = new List { 21, 46, 46, 55, 17, 21, 55, 55 };
IEnumerable distinctAges = ages.Distinct();
Console.WriteLine("Distinct ages:");
foreach (int age in distinctAges)
{
Console.WriteLine(age);
}
/*
This code produces the following output:
Distinct ages:
21
46
55
17
*/