Question

I have a list of:

class test
{
    name,
    timestamp
}

and I’d like to get all the last (newest) tests that have the same name. Many tests have same timestamp.

Eg:

name1, 2012-10-25 3:00PM
name1, 2012-10-25 3:00PM
name2, 2012-10-25 3:05PM
name2, 2012-10-25 3:05PM
name1, 2012-10-25 3:10PM
name1, 2012-10-25 3:10PM
name2, 2012-10-25 3:15PM
name2, 2012-10-25 3:15PM

I only need to get the last tests for each name:

name1, 2012-10-25 3:10PM
name1, 2012-10-25 3:10PM
name2, 2012-10-25 3:15PM
name2, 2012-10-25 3:15PM

Answer 1

Try this:

var q = from l in list
        group l by l.Name into g
        select new
        {
            Name = g.Key,
            Max = g.Max (x => x.Timestamp)
        } into x
        from y in list 
        where x.Name == y.Name && x.Max == y.Timestamp
        select y;

What happens here is first a grouping on list by Name, and doing that I select for each group the max Timestamp. This goes into x. Then I rejoin the same list to the grouped one, matching all the pairs from the grouping, this way I’m selecting all the original items matching the grouped items.