Best Features for C# Language (2.0-9.0)

 C# 2.0 language: 

Generics, nullable types, anonymous methods etc.

C# 3.0 language: 

LINQ, extension methods, lambda expressions, var (implicit types), get/set shortcuts etc.

C# 4.0 language: 

dynamic (late binding), optional arguments, covariance and contravariance in collections etc. 

C# 5.0 language: 

async/await, Caller Info

C# 6.0 language: 

string interpolation, dictionary initializer, nameof, using static

c# 7.0 Language

Span, ref struct, in, out, 

C# 8.0 Language

Async Streaming, Patterns, indices and range

C# 9.0 Language

        record, Covariant return types, Lambda discard parameters