I have a List of items of type DataItem (List<DataItem>):
public class DataItem
{
    public DataItem() { }
    public string Title { get; set; }
    public string Url { get; set; }
    public string Category { get; set; }
}
There may be many items with the same string in Category field. 
How can I extract a list of different possible categories using Linq?
What I want as a result is a List<string> which has all the values found for Category property, but doesn't have repeated values.
 
     
    