Question

Using Linq; how can I do the “opposite” of Take?

I.e. instead of getting the first n elements such as in

aCollection.Take(n)

I want to get everything but the last n elements. Something like

aCollection.Leave(n)

(Don’t ask why 🙂

Edit

I suppose I can do it this way aCollection.TakeWhile((x, index) => index < aCollection.Count - n) Or in the form of an extension

public static IEnumerable<TSource> Leave<TSource>(this IEnumerable<TSource> source, int n) 
{ 
  return source.TakeWhile((x, index) => index < source.Count() - n); 
}

But in the case of Linq to SQL or NHibernate Linq it would have been nice if the generated SQL took care of it and generated something like (for SQL Server/T-SQL)

SELECT TOP(SELECT COUNT(*) -@n FROM ATable) * FROM ATable Or some other more clever SQL implementation.

I suppose there is nothing like it?
(But the edit was actually not part of the question.)

Answer 1

aCollection.Take(aCollection.Count() - n);

EDIT: Just as a piece of interesting information which came up in the comments – you may think that the IEnumerable‘s extension method .Count() is slow, because it would iterate through all elements. But in case the actual object implements ICollection or ICollection<T>, it will just use the .Count property which should be O(1). So performance will not suffer in that case.

You can see the source code of IEnumerable.Count() at TypeDescriptor.net.