The biggest improvement in this release is support for C++/CLI (AKA “managed C++”). The changes for C++/CLI are primarily in Visual Studio. 

Upgrading Windows Desktop Applications with .NET Core 3 

Building Workflow Driven .NET Core Applications with Elsa

This is greatly reducing the fixed Array.Copy overhead for common cases. E.g. Copying byte array of length one:

• Array.Copy(Array, Array, int): 2.3x faster
• Array.Copy(Array, int, Array, int, int): 1.5x faster 

Creating NuGet packages in dotnet core 

Automatic reports for vulnerable ASP.NET Core runtimes 

.NEXT (dotNext) is the family of powerful libaries aimed to improve  development productivity and extend .NET API with unique features which potentially will be implemented in the next versions of C# compiler or .NET Runtime.

Announcing Prise, a plugin framework for .NET Core 

The Battle of C# to JSON Serializers in .NET Core 3