Major features of C# are Object-oriented programming, Strong Types, Standard Library, Properties, Events & Delegates, Linq, etc
Features of C# 9.0
Features of C# 9.0 1) Records 2) Init-Only Properties 3) Top Level Statements 4) Target-Typed New Expressions 5) Improved Pattern Matching 6) Asynchronous Streams 7) Improved module support 8)Improved Nullable Reference Types
Features of C# 7.0
C# 7 was released in 2017 with several new features to the C# language. Some of the notable features of C# 7 which you will be interested in are here