"Most popular" GROUP BY in LINQ?
- by tags2k
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.
