what is this feature called in c# and which version of c# uses this

Question

I am using this line of code in my project and haven`t seen this syntax.

 internal static StringBuilder a(this StringBuilder sb, string b) => sb.Append(b).Ap         


        

Answer 1

internal static StringBuilder a(this StringBuilder sb, string b)

This part tells us that a is an extension method to StringBuilder. You can read more on extension methods here

=> sb.Append(b).Append("\n")

These are functions with no statement body. Instead, you implement them with an expression following the function declaration. This is new feature in C# 6. and called expression-bodied function members. You can read more about them here