Last week, Microsoft released the first release candidate for the upcoming .NET 9 framework, which includes a range of updates across its core components, such as the .NET Runtime, SDK, libraries, C#, and frameworks like ASP.NET Core and .NET MAUI.
Regarding the .NET libraries, new APIs were added to ClientWebSocketOptions and WebSocketCreationOptions, enabling developers to configure WebSocket pings and automatically terminate connections if no response is received within a specified timeframe.
Additionally, new types—ZLibCompressionOptions and BrotliCompressionOptions—have been introduced, providing more detailed control over compression levels and strategies. These additions offer greater flexibility compared to the previous CompressionLevel option.
For users working with TAR archives, the public property DataOffset has been introduced in System.Formats.Tar.TarEntry allows access to the position of data in the enclosing stream. This provides the location of the entry’s first data byte in the archive stream, making it easier to manage large TAR files, including concurrent access features.
From this version, LogLevel.Trace events generated by HttpClientFactory will now exclude header values by default. However, developers can log specific header values using the RedactLoggedHeaders helper method, enhancing privacy and security.
Furthermore, the new command dotnet workload history has been introduced. As explained, this command tracks the history of workload installations or modifications within a .NET SDK installation, offering insights into workload version changes over time. It is intended to assist users in managing workload versions more efficiently, as stated similar to Git’s reflog functionality.
The release candidate also introduces updates to ASP.NET Core, such as a keep-alive timeout for WebSockets, support for Keyed DI services in middleware, and improvements to SignalR distributed tracing, aiming to improve performance and simplify development workflows.
Interested readers can read more about ASP.NET Core RC1 updates in the latest and detailed InfoQ news article.
Regarding .NET MAUI the release focuses on addressing issues and stabilizing the platform in preparation for the general availability (GA) release. Among the new features is HorizontalTextAlignment.Justify, which provides additional text alignment options for Labels. Also, updates to HybridWebView are included, with a guide for developers upgrading from .NET 9 Preview 7 to RC1, especially about Invoking JavaScript methods from C#.
With a note that .NET for Android and iOS in this release are primarily focused on quality improvements, as reported this release requires Xcode 15.4 for building applications.
Lastly, looking into the community discussion for this release, an interesting conversation clarified that the Out-of-proc Meter wildcard listening feature is a new feature not previously available in either in-process or out-of-process scenarios.
Tarek Mahmoud Sayed, collaborator on .NET project, wrote the following:
The wildcard support is the new feature that was not supported in proc or out of proc. The sample showing the in-proc just for simplicity to show using the wildcard. You can still listen out-of-proc too and leverage the wildcard feature. We are working to make diagnostics tools like dotnet monitor to leverage the feature too. Let me know if there still anything unclear and I'll be happy to clarify more.
Interested readers can find more information about this version in the official release notes. Lastly, the .NET 9 Release Candidate 1 download is available for Linux, macOS, and Windows.