Extension Methods in C#

C# extension methods are a way to extend the functionality of existing classes, structures or interfaces without having to modify their source code. They are defined as static methods in a static class, and the first parameter of the method must be preceded by the this keyword, which indicates that the method is an extension method.

Tuples in C#

A tuple is a data structure that can store multiple values of different data types in a single unit. In C#, tuples are used to return multiple values from a method, or to store a group of values without creating a separate class.