You haven't given much to go on so far in respect to how your getting the data out of the database etc.
I have made a simple example that should help you get distinct values from the collection using lambda.
List<test> d = new List<test>();
for (int i = 0; i <= 5; i++)
{
d.Add(new TEst { ID=i, Name="Simon" });
}
d.Add(new TEst { ID = 1, Name = "Simon" });
var x = (from s in d select s).Distinct();
Definition for the TEst class
public class TEst
{
public int ID { get; set; }
public string Name { get; set; }
}