Microsoft has officially rolled out the first preview of .NET 10, a significant update to its flagship software development platform. The new version, expected to arrive as a production release in November, brings a plethora of enhancements to the .NET runtime, SDK, libraries, C#, F#, ASP.NET Core, Blazor, and .NET MAUI.

The .NET 10 Preview 1, unveiled on February 25, can be downloaded from dotnet.microsoft.com. One of the key highlights of this release is C# 14, which introduces first-class support for System.Span<T> and System.ReadOnlySpan<T> in the language. This feature enables more natural programming with these types, boosting performance without compromising safety.

In addition to the C# 14 enhancements, the .NET 10 runtime has been optimized to reduce the abstraction overhead of popular language features. The just-in-time (JIT) compiler's ability to de-virtualize method calls has been expanded to cover array interface methods, resulting in improved performance. Furthermore, the JIT will stack-allocate small, fixed-sized arrays of value types that do not contain garbage collection pointers when it can guarantee the object will not outlive its parent method.

The .NET 10 libraries have also received significant updates, including the introduction of APIs that work with spans of characters, expanding normalization beyond string types and helping to avoid unnecessary allocations. Additionally, APIs for making left-handed transformation matrices have been added for billboard and constrained billboard matrices, and improvements have been made to ZipArchive to improve performance and memory usage.

Other notable features and improvements in .NET 10 Preview 1 include better handling of generic unmanaged structs in F#, a type conversions cache, and a NuGet Audit feature in the .NET 10 SDK that can prune framework-provided package references not used by the project. Visual Basic has also been updated with unmanaged constraint support and respects the OverloadResolutionPriorityAttribute used to resolve ambiguities among method overloads.

ASP.NET Core has been enhanced with support for generating OpenAPI 3.1 documents, a significant update to the OpenAPI specification, with full support for JSON Schema draft 2020-12. OpenAPI documents can now also be generated in the YAML format. The RouteAttribute in Blazor now supports route syntax highlighting to help visualize the structure of the route template.

Entity Framework has been updated with first-class LINQ support for the LeftJoin method, making those queries simpler to write. Finally, .NET MAUI ships as a .NET workload and multiple NuGet packages, allowing developers to easily pin projects to specific versions and to easily preview unreleased or experimental builds.

The release of .NET 10 Preview 1 marks a significant milestone in Microsoft's ongoing efforts to improve its software development platform. With its focus on performance, security, and developer productivity, .NET 10 is poised to have a major impact on the development community. As the platform continues to evolve, it will be interesting to see how developers leverage these new features and improvements to build innovative applications and services.

With the production release of .NET 10 expected in November, developers can start exploring the new features and enhancements in the preview version. As the platform continues to mature, it's clear that Microsoft is committed to delivering a world-class development experience for its users.