Last week Microsoft released .NET Core 3.0 Preview 7 for Windows, macOS, and Linux.
This release marks the beginning of the freezing period for .NET Core. From this point on, no more new features will be added and the development team will focus on polishing the existing code. According to the official announcement, a singular focus on quality is expected for the remaining preview releases.
The main improvement in this release is related to the size of the .NET Core SDK, which was reduced to 25%-30% of its original size (on-disk, depending on the operating system). The improvements come from a change on how the SDK is constructed: in previous versions, the SDK construction process involved using NuGet packages, which ended up in many unused artifacts. The new version of the SDK is constructed with what Microsoft calls "purpose-built packs", exemplified by reference assemblies, frameworks, and templates.
The size improvements are smaller for Windows since WPF and Windows Forms 3.0 were added as part of .NET Core 3.0. Nevertheless, the .NET Core SDK Docker images were also affected: the x64 Debian and Alpine images were respectively reduced to 45% and 30% of their original size. More details on the SDK size reduction can be found here.
This preview of .NET Core 3.0 is supported by Microsoft and can be used in production: the Microsoft .NET Site has already been updated with the new release. Another update for Preview 8 is expected in a couple of weeks. Microsoft states that very few changes should be made for most APIs after Preview 7. However, WPF, Windows Forms, Blazor and Entity Framework are listed as "notable exceptions" in the same statement.
According to the .NET Core roadmap, the final 3.0 release is scheduled for September 2019. With Preview 7, Microsoft officially recommends the start of adoption planning for .NET Core 3.0, especially if docker containers are being used in production. The improvements for containers in the new release can be found here, and they are primarily related to docker resource limits and orchestration.
