Microsoft has previewed .NET 10, which will be a long-term support release, with new features including a first look at C# 14.

The release notes for .NET 10 Preview 1 show enhancements across the .NET platform, including the runtime, core libraries, Entity Framework, the C#, F# and Visual Basic languages, ASP.NET, Windows Forms, Windows Presentation Foundation (WPF), and MAUI (Multi-Platform App UI).   

The usual release cycle for .NET includes a series of previews during which features are added, followed by a first release candidate around September and full release in November. Further new .NET 10 features can therefore be expected in due course.

Zip compression is more efficient in the new .NET 10 libraries, with faster performance and lower memory use. One particular case, adding a 2GB file to an existing archive, shows a 99.8 percent reduction in execution time and an even larger reduction in memory usage, according to the update documentation.

ASP.NET now has built-in OpenAPI 3.1 support, which will become the default for generated OpenAPI documents, described as a “significant update to the OpenAPI specification.”  

The JavaScript implementing the Blazor framework will now be shipped as a static web asset, allowing compression and reducing its size by 76 percent.

C# 14 includes field-backed properties, already previewed in C# 13. In C#, properties are often defined using an abbreviated form, with a hidden field that stores the property value. The new field keyword gives coders access to that property, while still using the concise property definition. 

Another likely C# 14 feature, extension members, is listed as in progress but not shipped in this preview.

Windows Forms, still popular for desktop Windows applications, is getting new clipboard APIs using JSON serialization to overcome security issues with BinaryFormatter.

Entity Framework is getting a new LeftJoin method for LINQ (Language Integrated Query), simplifying code that performs this type of query.

When it comes to .NET MAUI (multi-platform app UI) the team remains focused on “quality improvements” which one could interpret either as a necessary response to developer concerns, or as lack of activity. Product quality was also the focus of .NET MAUI changes in .NET 9, though developers did also get the important HybridWebView component.

Developers keen to try .NET 10 should download the new SDK and use it either with the preview version of Visual Studio, or with Visual Studio Code and the C# Dev Kit.