What is the difference between Single() and First() extension methods

What is the difference between Single() and First() extension methods in LINQ?

Answer»

Single()	First()
Used to RETURN a single specific ELEMENT of a query or a DEFAULT value if no result is found.	It is used to return the first element of any query with MULTIPLE values.
Used when exactly one element is expected as a result.	Used when there are multiple result expectations but you only NEED the first value.