Response Compression for both classic ASP.NET MVC and ASP.NET Core
In ASP.NET Core we have the QueryHelpers class for automatically creating QueryStrings. No more dealing with encoding/decoding strings, ampersand and question marks manually!
The new C# 8.0 Tuple Patterns are a very convenient way to allow matching of more than one value in a single pattern matching expression.
The new C# 8.0 switch expressions are a very convenient way to map information in a compact fashion.