Try Grouping them:
List<T1> list1 = new List<T1>();
list1.Add(new T1 { RegionID = 1, Region = "Paris" });
list1.Add(new T1 { RegionID = 2, Region = "Canada" });
list1.Add(new T1 { RegionID = 3, Region = "UK" });
list1.Add(new T1 { RegionID = 4, Region = "Paris" });
list1.Add(new T1 { RegionID = 5, Region = "Canada" });
list1.Add(new T1 { RegionID = 6, Region = "London" });
var list = from ta in list1
group ta by ta.Region into newgroup
orderby newgroup.Key
select newgroup;
foreach (var t in list)
{
T1 t1 = t.First();
Console.WriteLine("{0}:{1}", t1.RegionID, t1.Region);
}