How to select last record in a LINQ GroupBy clause

Question

I have the following simple table with ID, ContactId and Comment.

I want to select records and GroupBy contactId. I used this LINQ extension method statement:

Mains.GroupBy(l => l.ContactID)
 .Select(g => g.FirstOrDefault())
 .ToList()

It returns record 1 and 4. How can I use LINQ to get the ContactID with the highest ID? (i.e. return 3 and 6)

Answer 1

You can order you items

Mains.GroupBy(l => l.ContactID)
.Select(g=>g.OrderByDescending(c=>c.ID).FirstOrDefault()) 
.ToList()