Question

I have a list with the following info

date, name, and a few statistics

The names can repeat, but they don’t necessarily.

so for instance I could have

5, today, “John”
4, today, “Kim”
3, today, “Peter”
2, yesterday, “Kim”
1, yesterday, “Tim”

I want a query that retrieves the latest records for each user. In my example that would be records 5, 4 and 1.

Do I necessarily have to match each record against the whole database in order to find out?
What would be the best performing query to achieve this?

Answer 1

Maybe something like this could work?

var linq = people.GroupBy(a => a.Name).Select(a => a.OrderBy(a => a.Date).Last());

Longer version:

var linq = from person in people
           group person by person.Name into grouped
           select grouped.OrderBy(a => a.Date).Last();