Your AI-generated monthly roundup of .NET platform updates and community highlights.
Welcome to the December 2025 edition of Pulse on .NET, where we recap the latest updates from Microsoft’s official releases and the broader .NET ecosystem over the past month. December followed on the heels of November’s landmark .NET 10 launch, meaning this month was all about consolidation, community exploration, and gearing up for the new year. Microsoft delivered the first servicing patches for .NET 10, Visual Studio, and associated tools, while the community enthusiastically dug into .NET 10’s new capabilities – from C# 14 language features to AI integration. In this edition, we’ll cover core releases and fixes (ensuring a smooth start for .NET 10 LTS users), the tooling updates across IDEs and cloud platforms that accompanied these releases, notable open-source and ecosystem developments (including updates from the .NET Foundation and third-party frameworks), plus community highlights like blog posts, events, and our traditional end-of-year advent series. Let’s dive in.
To set the stage, here’s a quick summary of December’s most significant .NET-related updates, grouped by category:
| Category | Update | Release Date | Highlights |
|---|---|---|---|
| Releases | .NET 10.0.1 (Servicing) | December 9, 2025 | First patch for .NET 10 LTS – non-security fixes only [devblogs.m…rosoft.com] (misc. reliability improvements). No new features or breaking changes, keeping .NET 10 stable for early adopters. (.NET 8/9 had no new December patches) [devblogs.m…rosoft.com]. |
| Releases | SharePoint Framework 1.22 | December 29, 2025 | Major update to SPFx dev tooling: migrated build system from Gulp to Heft for modern JS tooling alignment [infoq.com], [infoq.com]. Cleans up legacy template vulnerabilities and resets default TypeScript to 5.8, preparing SharePoint devs for more secure, up-to-date workflows. No API breaking changes, but Gulp support now legacy (to be phased out in future releases) [infoq.com]. |
| Tooling | Visual Studio 2026 v18.1 | December 9, 2025 | First update to VS2026 (the new AI-powered IDE). Focus on performance and stability: faster solution load and debugging, fewer UI freezes [infoq.com]. Deep GitHub Copilot integration was refined based on early feedback (better AI code suggestions, improved “agent” modes) [infoq.com]. Maintains full backward compatibility with VS2022 projects and extensions [infoq.com]. |
| Tooling | JetBrains Rider 2025.3 | Released late Nov 2025 | JetBrains’ .NET IDE shipped its Q4 update alongside .NET 10’s launch, with day-one support for .NET 10 and C# 14 [blog.jetbrains.com]. This means .NET 10 projects and new C# 14 syntax (extension members, compound assignment operators, etc.) are fully supported in Rider and ReSharper out of the box [blog.jetbrains.com]. The 2025.3 release also introduced a new default UI theme and significant startup performance improvements for .NET developers [blog.jetbrains.com]. |
| Tooling | AWS “Transform” GA | December 1, 2025 | Amazon Web Services launched AWS Transform – a tool to help modernize .NET applications. Now generally available, it can automatically port legacy .NET Framework apps to .NET 10 (or .NET Standard), including migrating ASP.NET Web Forms UIs to Blazor on ASP.NET Core [aws.amazon.com]. It integrates into Visual Studio 2026/2022 via an updated AWS Toolkit, providing an interactive transformation plan with progress updates and even “Next Steps” guidance for using AI assistants to finish the job [aws.amazon.com]. This offering shows even AWS is embracing .NET 10 support, giving developers more options to modernize on the latest .NET platform. |
| Ecosystem | Third-Party Libraries | December 2025 | The .NET ecosystem’s major libraries and frameworks rolled out updates to support .NET 10. For instance, the Uno Platform had shipped v6.4 with day-one .NET 10 compatibility in November, and December saw smaller maintenances aligning with VS2026’s new project format [manorrock.com]. The Avalonia UI framework released v11.3.10 (Dec 18) as a fully .NET 10-compatible update, smoothing out WPF-like cross-platform development on the new runtime. Likewise, popular tools like Serilog, AutoMapper, and Polly published minor updates ensuring they run flawlessly on .NET 10. Component vendors were busy too – e.g. Telerik, DevExpress, and ComponentOne all shipped their Q4 2025 suites with .NET 10 support (Telerik Reporting 2025 R4, ComponentOne 2025v2, etc.), bringing new features like improved reporting templates and WPF 3D charting while guaranteeing compatibility. In short, by year’s end the vast majority of third-party tools – from UI controls to logging frameworks – had been tested and updated for .NET 10, making it easier for developers to upgrade their apps. |
| Community | Content & Blogs | December 2025 | Community contributors churned out deep-dives and how-tos to help everyone digest .NET 10’s new features. Notable blog posts included “.NET 10 Breaking Changes to Watch For” by Khalid Abuhakmeh (guidance on smooth upgrades), “Easier Reflection with [UnsafeAccessorType]” by Andrew Lock (explaining a new C# 14 attribute) [blog.jetbrains.com], and “Null-conditional Assignment in C# 14” by Thomas Claudius Huber [blog.jetbrains.com]. Video content was rich too – YouTuber Nick Chapsas discussed big breaking changes in .NET 10 (while reassuring viewers on workarounds) [blog.jetbrains.com], and David Giard’s “Technology and Friends” podcast featured Jimmy Bogard talking about Monetizing Open Source in the .NET world [blog.jetbrains.com]. On the official side, Microsoft’s .NET Blog capped off the year with a special post, “Top .NET Blog Posts of 2025”, curating the year’s highlights: from the .NET 10 launch and performance tips to AI tutorials and new CLI tricks [devblogs.m…rosoft.com], [devblogs.m…rosoft.com]. It’s a great reading list for anyone who missed those posts throughout the year. |
| Community | Events & Initiatives | December 2025 | .NET developers kept the learning momentum going through the holiday season. Advent calendars – a beloved December tradition – were in full swing. The C# Advent 2025 brought daily blog posts by community members on diverse .NET topics (from cryptography in .NET 10 to building Christmas-themed apps with Spectre.Console). Similarly, F# enthusiasts delivered a #FsAdvent series, sharing one F# tip or project per day, as organized by Sergey Tihon [blog.jetbrains.com]. Many developers also participated in Advent of Code 2025, solving daily coding puzzles in C# and F#, and sharing their solutions on GitHub – a fun way to exercise new language features. In meetups, .NET user groups worldwide held year-end gatherings (both in-person and virtual) to discuss experiences with .NET 10 and celebrate the community. The .NET Foundation hosted an episode of its Community Standup “Community Talks” on Dec 18: “AI-Powered .NET Apps with ABP & Microsoft Agent Framework” [dotnetfoundation.org]. In that session, the team behind the open-source ABP web framework demoed how they’re integrating .NET’s new AI libraries and the Agent Framework into real-world enterprise applications – showing a practical path for developers to add intelligent agents and semantic functions to their own .NET projects. This mix of holiday creativity and cutting-edge tech discussions truly showcased the passion and breadth of the .NET community. |
Table: December 2025’s key .NET updates and highlights, by category (official releases, tooling, ecosystem, community). [devblogs.m…rosoft.com], [infoq.com]
.NET 10 (LTS) enjoyed its first full month of life, and Microsoft issued the initial servicing update to address early feedback. On December 9th (the usual “Patch Tuesday”), they released .NET 10.0.1 across the runtime, ASP.NET Core, Entity Framework Core, and SDK. According to the .NET team’s release notes, this refresh contained only non-security fixes – essentially polishing the .NET 10 runtime and libraries without introducing new features. This is typical for a first patch: it resolved minor bugs and performance hiccups discovered after the big launch. Developers who jumped on .NET 10 right away were encouraged to upgrade to 10.0.1 to benefit from those fixes. There were no December updates for .NET 8 or .NET 9, since those got their final servicing releases alongside .NET 10’s launch in November and had no pressing issues pending. The .NET Framework also had no new patches in December (its next scheduled update will be in early 2026). Overall, .NET 10’s early stability looked good – the lack of urgent hotfixes or security patches indicates a smooth rollout for the LTS. Enterprise users still evaluating .NET 10 can head into the new year confident that it’s off to a solid start. [devblogs.m…rosoft.com]
On the Visual Studio side, December saw the first post-launch updates to Visual Studio 2026. Microsoft delivered VS 2026 version 18.1 to the Stable channel, roughly one month after the IDE’s GA. This update was all about refinement and performance. InfoQ reported that VS 2026’s 18.1 release brought significant speed-ups in large .NET solution load times and debugger responsiveness, addressing some pain points from the preview period. Cold startup for debugging was improved, and various actions that previously could make the IDE unresponsive (especially with big projects) were optimized or moved off the UI thread. Users noticed the IDE feeling snappier and more fluid when working on sizable codebases. The update also included tweaks to the deeply integrated GitHub Copilot AI: better handling of multi-line suggestions and “Copilot chat” queries referencing specific code context, based on early adopter feedback. At the UI level, VS 2026’s new Fluent-inspired interface got minor polish, and a couple of bugs (like high-DPI scaling issues) were fixed. Importantly, this update did not break extension compatibility – all VS 2022 extensions remained compatible with 2026, which lowered friction for folks upgrading. With 18.1, Visual Studio 2026 enters 2026 with improved stability, fulfilling Microsoft’s promise of an “even faster and more reliable” AI-enhanced IDE. [infoq.com]
Outside of the core .NET/VS releases, a noteworthy official release in December was in the Microsoft 365 developer space: SharePoint Framework (SPFx) 1.22 was announced on December 29th. SPFx is the client-side dev model for building web parts and extensions in Microsoft 365, and while it targets web tech, many .NET developers follow it for enterprise SharePoint solutions. SPFx 1.22’s significance is that it modernized the build toolchain underlying SharePoint web part projects. Microsoft dropped the long-standing Gulp-based build system in favor of Heft (a newer, config-driven build orchestrator from the Rush Stack) to align with modern JavaScript workflows. This was a big engineering effort meant to eliminate technical debt – Gulp in SPFx hadn’t kept up with evolving Node.js toolchains, leading to security warnings (npm audit issues) in project templates. The new Heft-based pipeline cleans up those vulnerabilities and provides a more transparent, extensible build process for SharePoint devs. It’s essentially a foundational update: existing projects can still build with Gulp for now, but new SPFx projects will default to Heft, and in future versions Gulp will be fully deprecated. Along with the build switch, SPFx 1.22 updates the baseline dependencies (like using TypeScript 5.8, and refreshing Yeoman generator outputs to remove outdated packages). No new user-facing features were added, but this release was well-received in the Microsoft 365 community – it shows an investment in keeping that dev platform current. For .NET developers, it’s a reminder that the Microsoft ecosystem beyond .NET itself (like Office development) is also evolving, often embracing modern frameworks and build tools to improve developer experience. [infoq.com]
December’s tooling updates illustrated the wider ecosystem’s rapid response to .NET 10. Not only did Microsoft’s own tools (VS, etc.) get updates, but third-party IDEs and cloud services also delivered support, ensuring developers have a full toolbox for the new year.
JetBrains was quick off the mark with its .NET tooling. At the end of November, coinciding with .NET 10’s release, JetBrains shipped Rider 2025.3 and ReSharper 2025.3, and through December these became the go-to versions for JetBrains users on .NET 10. The headline was “Day-zero support” for .NET 10 and C# 14 – meaning that from the day .NET 10 launched, Rider (an alternative cross-platform IDE) could create, run, and debug .NET 10 projects seamlessly. All the new C# 14 language features (like extension members/properties and the field keyword enhancements) were fully understood by Rider’s code analysis and refactoring engine. This allowed developers who prefer Rider to upgrade to .NET 10 without waiting. JetBrains also took that opportunity to roll out some welcome quality-of-life improvements in Rider 2025.3: a new default UI theme (“Islands”) that refreshes the IDE’s look and feel, and performance optimizations reducing solution load times. Many .NET devs using Rider noted faster startup and less UI flicker during project open, which boosts productivity. Likewise, ReSharper (JetBrains’ popular Visual Studio extension for advanced refactorings and analysis) received updates for C# 14 and VS2026 compatibility. By December’s end, Rider and ReSharper users were confidently using .NET 10 – a testament to JetBrains’ commitment to timely updates. JetBrains even blogged about how their tools integrate new C# features, ensuring that features like extension operators had proper inspections and quick-fixes in place. All of this meant the .NET ecosystem’s IDE diversity remained strong: whether you use Visual Studio, VS Code, or Rider, you had full support for the latest .NET. [blog.jetbrains.com] [blog.jetbrains.com], [blog.jetbrains.com]
On the open-source tooling front, many specialized frameworks and runtime extensions also kept in step. One notable area is AWS’s support for .NET, which advanced significantly this month. On December 1, AWS announced that its Porting Assistant efforts had culminated in a new product called AWS Transform (GA release) aimed at automating .NET application modernization. This service can scan an old .NET Framework application and convert it to .NET 10, handling common API changes, project file updates, and even UI transformations. In particular, AWS highlighted a feature to migrate ASP.NET Web Forms UIs to Blazor on .NET (which is remarkable, since Web Forms was a legacy web tech not directly supported on .NET Core). The tool works through an extension in Visual Studio, guiding developers with a customizable transformation plan – you can review what it will do, run the conversion, and get a detailed report of what was changed and what might need manual follow-up. It even generates a “Next Steps” Markdown file listing any remaining tasks and suggests using AI assistants (AWS mentions a tool called Kiro in this context) to help complete the modernization. Essentially, AWS is providing a free path to move off old .NET versions onto .NET 10 on AWS’s cloud. This aligns with what we saw at .NET Conf (where AWS made a surprise appearance to encourage .NET modernization) – AWS wants to make sure .NET developers can run modern .NET on AWS easily. To top it off, although it actually happened right after December (in early January 2026), it’s worth noting that AWS Lambda announced official support for .NET 10 as a runtime, showing the momentum: by New Year, .NET 10 was available on all major cloud platforms (Azure App Services had .NET 10 from day one, and now AWS Lambda does too). The bottom line is cross-platform and cloud tooling for .NET 10 matured quickly, so enterprise developers have the confidence that all their favorite environments (whether on Azure, AWS, or on-premises with third-party tools) are ready for .NET 10. [aws.amazon.com]
Meanwhile, other tools and runtimes important to .NET developers saw updates: PowerShell 7.6 continued in preview through December (PowerShell 7.6 Preview.6 was released Dec 11), preparing PowerShell – which is built on .NET – to align with new .NET runtime improvements in the coming year. And Azure DevOps (ADO) users received their regular sprint updates; nothing drastic changed in ADO in December, but it quietly added support for the new slnx solution format of VS2026 in its pipelines and improved .NET 10 build agents, so CI/CD didn’t miss a beat. For Visual Studio Code users, the C# extension (now powered by the Roslyn-based language server) was already .NET 10-ready; December’s VS Code update was minor, focusing on bug fixes in the editor, but .NET devs using VS Code were happily writing C# 14 code with full IntelliSense and debugging support. In short, by end of 2025, the entire tool chain – from editors and build systems to cloud services – had moved to support .NET 10. This rapid enablement was a huge win for developers: the new features and performance of .NET 10 could be used in daily work without waiting for environment support.
The .NET open-source ecosystem is vast, and December brought a flurry of activity as maintainers integrated the recent platform updates and even pushed into new realms like AI enablement. Here are some of the ecosystem highlights:
Uno Platform & MAUI Community: In November, the Uno Platform (an open-source cross-platform UI framework) had already delivered Uno v6.4 with .NET 10 support and an AI-powered UX tool. In December, the focus shifted to community toolkits around .NET MAUI (the official multi-platform UI). The .NET MAUI Community Toolkit held its monthly stand-up, demonstrating new contributions and discussing .NET 10 adoption. The community is actively improving MAUI with .NET 10 – for example, adding support for XAML improvements (like source generators and markup enhancements that .NET 10 enables). An interesting crossover came via an Uno Platform community video titled “Uno Platform, Now with AI”, showing how Uno’s integration of AI (through its Hot Reload “Design Agent”) worked in practice. This indicates a trend: UI frameworks are leveraging AI assistants to boost developer productivity (suggesting UI changes, generating XAML, etc.). By year’s end, both MAUI and Uno (as well as community favorites like Avalonia, which released updates in mid-December) had solid support for .NET 10 – meaning developers building client apps can use the new runtime confidently. Avalonia’s December 18 release (v11.3.10) addressed some compatibility issues and ensured its WPF-like UI toolkit runs smoothly on .NET 10, while also adding features like better composition animations. It even includes preliminary support for Visual Studio 2026. Another sign of ecosystem health: Avalonia announced a partnership with the .NET MAUI team to bring MAUI support to Linux and WebAssembly via Avalonia rendering – a fascinating collaboration bridging frameworks. [manorrock.com] [devblogs.m…rosoft.com]
Web and Cloud Frameworks: On the server/web side, December saw continued community engagement with ASP.NET Core improvements. InfoQ’s mid-December article “ASP.NET Core in .NET 10: Major Updates across Blazor, APIs, and OpenAPI” dissected the comprehensive enhancements delivered with .NET 10. This kept the discussion alive around features like built-in Minimal API validation, OpenAPI 3.1 support, and Blazor updates. While these were released with .NET 10, community bloggers and presenters took December as an opportunity to explain and demo them. For example, some blog posts and YouTube streams walked through using the new TypedResults.ServerSentEvents for server-sent events streaming in ASP.NET Core (an exciting addition for real-time scenarios), and the revamped passkey authentication support in ASP.NET Identity (thumbs-up from security-conscious devs). The Azure SDK team did not release a new Azure .NET SDK wave in December (their last big release was November), but many Azure services were updating documentation and samples for .NET 10 – e.g., Azure Functions had a preview for .NET 10 support still ongoing (expected GA early 2026), and Azure Service Fabric’s runtime declared compatibility with .NET 10 for guest executables. In the microservices arena, projects like Dapr (Distributed Application Runtime) and Orleans were mentioned frequently in community channels as people evaluated how .NET 10’s improvements (especially performance) benefit distributed systems. Visual Studio Magazine ran a Q\&A in mid-December, “Busy .NET Developer’s Guide to Orleans”, highlighting Orleans (a virtual actor framework) as a key tech to watch in 2025 for scaling .NET applications. While Orleans itself didn’t have a new version in Dec (Orleans 7 was previously released), the article and others underscored that orchestrating cloud-native apps in .NET is a hot topic, boosted by frameworks like Orleans and Dapr now fully compatible with .NET 10 out-of-the-box. [infoq.com], [infoq.com]
AI and Machine Learning: .NET’s push into AI continued to resonate through the ecosystem. The Microsoft ML.NET team quietly released ML.NET 3.0 in late November with .NET 10 support, and in December we saw community exploration of ML.NET’s new capabilities (like better ONNX model integration). However, the spotlight in AI was really on the Agent Framework and MCP (Model Context Protocol) introduced at .NET Conf. December’s community talk (with the ABP Framework) showed real-world usage of the Microsoft AI SDKs in a popular open-source web framework. The ABP team demoed an “AI Management Module” for their framework that leverages Semantic Kernel and the Agent Framework to let developers define AI-driven workflows in business applications. This is a concrete example of how the new AI features can be used beyond demos – ABP is providing out-of-the-box support so that, say, an enterprise app built on ABP could have an “AI Agent” that takes user requests and coordinates tasks using the same tech as in the Agent Framework preview. The community reaction has been positive – a lot of developers are keen to experiment with AI in the context of their normal apps, not just in isolation. We also saw smaller open-source projects integrating AI: for instance, a project called GPT-OSS published a guide on using local LLMs with C# (leveraging the Ollama tool), and the .NET AI SDK (which includes Microsoft.Extensions.AI) got some incremental updates based on feedback, improving how dependency injection works for AI services. All told, the .NET ecosystem is beginning to blend AI capabilities into standard frameworks and libraries, signaling that in 2026, AI won’t be a niche add-on but rather a common ingredient in .NET applications. [dotnetfoundation.org] [devblogs.m…rosoft.com]
DevOps and SecOps: Another ecosystem angle is security and DevOps. December being year-end, Microsoft didn’t introduce new DevOps services, but we did note that .NET’s open-source security posture got a nod: on Dec 11, InfoQ reported that the internal OpenAPI.NET library used by ASP.NET was upgraded in .NET 10, and part of that included removing some older cryptographic algorithms and improving default security headers. In practice, this means .NET 10 apps have a slightly stronger security baseline out-of-the-box (e.g., stricter CSP in Blazor, automatic HTTP eviction of old TLS, etc.). The .NET Foundation’s Project “Security Group” (launched earlier in the year to coordinate vulnerability response across the community) didn’t have to spring into action in December – there were no major vulns disclosed – but they did publish guidance reminding library authors how to push out coordinated security patches if needed. And since December’s Patch Tuesday included some Windows/.NET related fixes (none in .NET runtime itself, but a few in Visual Studio installers and one in ASP.NET’s JWT handling), enterprise devs were advised by security blogs to update before the holiday break. The .NET community shows maturity in security: we saw proactive moves like the Open Source Security Foundation (OpenSSF) folks working with .NET projects to implement supply-chain security (several .NET OSS repos adopted Sigstore and other signing practices by end of 2025). It’s not headline-grabbing, but it’s critical groundwork that was happening behind the scenes throughout the ecosystem. [infoq.com], [infoq.com]
In summary, December saw the .NET ecosystem enthusiastically adopting .NET 10 and extending it – whether through UI frameworks enabling new platforms, web frameworks integrating AI, or cloud tools easing migrations. It’s clear that .NET 10’s influence is rippling outward: by the time we head into 2026, nearly every major library, framework, and service used by .NET developers has incorporated support for the new runtime, and many are finding innovative ways to leverage .NET’s latest features (especially around AI and performance).
The .NET developer community truly shined in December, sharing knowledge and celebrating the year’s achievements. With .NET 10 being such a significant release, many community members focused on creating content to help others learn and transition smoothly. Here are some of the top community-driven highlights from the month:
🔖 Top Blog Posts & Tutorials – A wave of blog posts from both well-known experts and newer voices provided deep dives into specific .NET 10 features:
[UnsafeAccessorType] attribute in C# 14. His post “Easier reflection with [UnsafeAccessorType] in .NET 10” explained how this attribute can simplify high-performance reflection scenarios by allowing access to private members safely, showcasing a before-and-after example that resonated with library authors. [blog.jetbrains.com]?=) in his blog, demonstrating how it can reduce boilerplate when initializing objects conditionally. [blog.jetbrains.com]All these posts, and many more, were shared widely on social media and aggregator sites like Reddit’s r/dotnet and Hacker News, generating healthy discussion. It’s clear that the community’s content creation in December was laser-focused on easing the transition to .NET 10 and showcasing its benefits.
opening syntax. The event also commemorated 10 years of F# open source (since 2015) – a bit of nostalgia along with forward-looking discussion.Through all these activities, the tone in the .NET community was optimistic and enthusiastic. Developers are clearly excited about the new capabilities in the platform and are actively helping each other learn. The shared experiences – whether solving puzzles, upgrading projects, or debating the merits of a new feature – brought the community closer. As 2025 turned into 2026, one could sense a collective pride in what the .NET ecosystem achieved this year, and eagerness for what’s coming next.
As we wrap up the December 2025 Pulse on .NET, we also wrap up a remarkable year for the .NET community. From shipping a major milestone release (.NET 10) to embracing AI and modern development practices, 2025 has been transformative. This month’s happenings solidified those advances and set the stage for an exciting 2026. Thank you for reading our monthly roundups and for being part of the .NET journey. Here’s to a Happy New Year – may 2026 bring even more innovation and joy to .NET developers everywhere! 🎉