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

Answer 1

OrderByDescending

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

is your best solution

It orders by the highest ID descending, which is pretty obvious from the name.