【转帖】Linq

http://stackoverflow.com/questions/250867/most-popular-group-by-in-linq

Assuming a table of tags like the stackoverflow question tags:

TagID (bigint), QuestionID (bigint), Tag (varchar)

What is the most efficient way to get the 25 most used tags using LINQ? In SQL, a simple GROUP BY will do:

SELECT Tag, COUNT(Tag) FROM Tags GROUP BY Tag

I've written some LINQ that works:

var groups = from t in DataContext.Tags group t by t.Tag into g              select new { Tag = g.Key, Frequency = g.Count() }; return groups.OrderByDescending(g => g.Frequency).Take(25);

Like, really? Isn't this mega-verbose? The sad thing is that I'm doing this to save a massive number of queries, as my Tag objects already contain a Frequency property that would otherwise need to check back with the database for every Tag if I actually used the property.

So I then parse these anonymous types back into Tag objects:

groups.OrderByDescending(g => g.Frequency).Take(25).ToList().ForEach(t => tags.Add(new Tag() { Tag = t.Tag, Frequency = t.Frequency }));

I'm a LINQ newbie, and this doesn't seem right. Please show me how it's really done