Test if an IEnumerable<T> contains 1 element without counting or using Single

Question

How can I find if my list contains one and only one item without Count or Single?

Possible dupe of Efficient Linq Enumerable's 'Count() == 1' test

Answer 1

How about this:

int limitedCount = myEnumerable.Take(2).Count();

That will give you:

• 0 if it was empty
• 1 if it had exactly 1 element
• 2 if it had 2 or more elements

... but it gives you those answers whilst only iterating over the sequence once. You can then switch on the results.

Answer 2

myEnumerable.Take(2).Count() < 2