Standard Query Operators are implemented as extension methods in .NET Framework. These Standard Query Operators can be used to work with any collection of objects that implements the IEnumerable interface. A class that inherits from the IEnumerable<t> interface must provide an enumerator for iterating over a collection of a specific type. All arrays implement IEnumerable<t>. Also, most of the generic collection classes implement IEnumerable<t> interface.