[Person] PersonID, EmailAddress, FirstName, LastName [OnlineAccount] OnlineAccountID, PersonID, Nickname
Each person is allowed to have 0-* OnlineAccount.
In entity framework with C#, how do I select the top 5 Person that has the most accounts?
var items = context.PersonSet.OrderByDescending(u => u.OnlineAccounts.Count).Take(5);
IQueryable<Person>. It doesn't return results yet, because it implements deferred execution. It will be translated to SQL and executed when needed:
var metarializedItems = items.ToList(); // ToList forces execution
foreach(var item in items) // foreach forces execution
Example above will translate to SQL similar to this one:
SELECT TOP 5 p.PersonID, p.EmailAddress, p.FirstName, p.LastName FROM Person p ORDER BY (SELECT COUNT(*) FROM OnlineAccount oa WHERE p.PersonID = oa.PersonID) DESC
It won't be this exact SQL. Different EF version may produce different SQLs, but I wrote it to ilustrate how it works.
Take(5) is translated to
OrderByDescending(u => u.OnlineAccounts.Count) is translated to
ORDER BY (SELECT COUNT(*) FROM OnlineAccount oa WHERE p.PersonID = oa.PersonID) DESC. This is power of Entity Framework. It translates .NET expressions to SQL.