c# - Efficient Linq Enumerable's 'Count() == 1' test

Question

Similar to this question but rephrased for Linq:

You can use Enumerable<T>.Any() to test if the enumerable contains data. But what's the efficient way to test if the enumerable contains a single value (i.e. Enumerable<T>.Count() == 1) or greater than a single value (i.e. Enumerable<T>.Count() > 1) without using an expensive count operation?

Answer 1

int constrainedCount = yourSequence.Take(2).Count();

// if constrainedCount == 0 then the sequence is empty
// if constrainedCount == 1 then the sequence contains a single element
// if constrainedCount == 2 then the sequence has more than one element