website

Pulse on .NET – March 2026 Edition

Your AI-generated monthly roundup of .NET platform updates and community highlights.

March 2026 proved to be one of the densest months outside a major launch cycle. .NET 11 Preview 2 arrived on March 10, giving the next release real shape with runtime-level async improvements, native OpenTelemetry tracing, and a host of SDK and library enhancements. In a separate announcement, the C# team previewed union types for C# 15 — a long-awaited language feature enabling exhaustive pattern matching over closed sets of types. Meanwhile, .NET 10 (LTS) demanded attention twice: a Patch Tuesday update (10.0.4) fixed three security vulnerabilities, followed two days later by an out-of-band 10.0.5 release correcting a macOS debugger regression. On the tooling front, Visual Studio 2026 v18.4 introduced custom Copilot agents and enterprise MCP governance, JetBrains shipped Rider 2026.1 with an ASM disassembly viewer and file-based C# support, and ReSharper arrived on VS Code after a year-long preview. The ecosystem delivered its own headline: .NET Aspire 13.2 launched at the inaugural Aspire Conf with over 1,100 closed issues, a TypeScript AppHost preview, and an AI-agent-native CLI. Community events like Visual Studio Live! Las Vegas and the .NET Foundation Board elections rounded out a month that advanced .NET on every front. Let’s break it all down. [devblogs.m…rosoft.com] [devblogs.m…rosoft.com] [devblogs.m…rosoft.com], [devblogs.m…rosoft.com] [devblogs.m…rosoft.com] [blog.jetbrains.com] [blog.jetbrains.com] [devblogs.m…rosoft.com], [gingter.org]

Key Updates in March 2026 by Category

Category Update Release Date Highlights
Releases .NET 11 Preview 2 & March Patches March 10, 2026 Second preview of .NET 11 — Runtime Async V2, JIT improvements, cached interface dispatch [devblogs.m…rosoft.com]; ASP.NET Core gains native OpenTelemetry tracing and Blazor TempData support [devblogs.m…rosoft.com]; EF Core adds LINQ MaxBy/MinBy translation and SQL Server DiskANN vector index support [devblogs.m…rosoft.com]; SDK container images up to 17% smaller [devblogs.m…rosoft.com]; F# gains #elif directive and overload resolution caching (type-checking drops from 6.5 s → 2.9 s in benchmarks) [infoq.com]. Released alongside .NET 10.0.4 (fixes 3 CVEs — CVE-2026-26130, -26127, -26131) [devblogs.m…rosoft.com] and .NET 10.0.5 OOB (macOS debugger crash regression fix) [devblogs.m…rosoft.com]. .NET Framework had no new updates [devblogs.m…rosoft.com].
Releases C# 15 Union Types (Preview) March 2026 The .NET Blog announced union types for C# 15 — developers can declare a closed set of case types with implicit conversions and compiler-enforced exhaustive switch expressions [devblogs.m…rosoft.com]. Sebastian Gingter’s analysis notes the syntax is simple (public union Pet(Cat, Dog, Bird);) and the enforcement turns unions “from a syntactic nicety into something genuinely useful in production code” [gingter.org]. This remains a preview with not all specification items implemented yet [gingter.org].
Tooling Visual Studio 2026 v18.4 March 10, 2026 March update delivers custom Copilot agents (.agent.md files in repos) with full workspace awareness and MCP connections [devblogs.m…rosoft.com]; Enterprise MCP governance via GitHub allowlists restricts AI to approved servers [devblogs.m…rosoft.com]; “Profile with Copilot” in Test Explorer auto-analyzes CPU/instrumentation data [devblogs.m…rosoft.com]; Perf Tips with live profiling show inline metrics during debugging [devblogs.m…rosoft.com]; new find_symbol tool gives agents language-aware symbol navigation for C#, C++, Razor, TypeScript [devblogs.m…rosoft.com]; Copilot fixes NuGet vulnerabilities from Solution Explorer [devblogs.m…rosoft.com]; JSON editor now ships with Core Editor (supports Draft 2020-12 / 2019-09) [htek.dev]; HTML rich copy/cut preserves syntax highlighting when pasting into web apps [devblogs.m…rosoft.com].
Tooling Azure Developer CLI (March 2026) March 2026 Seven releases (1.23.7–1.23.13) [devblogs.m…rosoft.com]: new azure.ai.agents extension for local AI agent run/debug and deployment to Microsoft Foundry [devblogs.m…rosoft.com]; Copilot integration in azd init for AI-assisted scaffolding [devblogs.m…rosoft.com]; Container App Jobs deployment via host: containerapp [devblogs.m…rosoft.com]; local preflight validation of Bicep parameters before deploying [devblogs.m…rosoft.com]; automatic pnpm/yarn detection and pyproject.toml support [devblogs.m…rosoft.com]; configurable per-service deployment timeouts [devblogs.m…rosoft.com].
Tooling JetBrains Rider 2026.1 (GA) March 30, 2026 Stable release bringing file-based C# programs (run .cs files without a project) [blog.jetbrains.com]; ASM Viewer for inspecting JIT, ReadyToRun, and NativeAOT output [blog.jetbrains.com]; NuGet Package Manager Console preview [blog.jetbrains.com]; Azure DevOps integration for cloning repos [blog.jetbrains.com]; ACP Registry for browsing and installing AI agents (Junie, Claude, Copilot, Cursor, etc.) [blog.jetbrains.com]; improved MAUI iOS dev on Windows with auto-configured Mac build hosts [blog.jetbrains.com]; Unreal Engine mobile debugging and Unity Profiler integration [blog.jetbrains.com].
Tooling ReSharper for VS Code March 5, 2026 Official release of ReSharper extension for VS Code, Cursor, Google Antigravity, and compatible editors [blog.jetbrains.com]: professional-grade C# inspections, refactoring, unit test runner (NUnit, xUnit, MSTest) [blog.jetbrains.com]; supports AI-generated code review [blog.jetbrains.com]; free for non-commercial use [blog.jetbrains.com]; next focus area: debugging support [blog.jetbrains.com].
Ecosystem Framework & Library Updates March 2026 .NET Aspire 13.2 (Mar 23): AI-agent-native CLI (aspire start/stop/ps/doctor/wait/export/secret), --isolated parallel environments, TypeScript AppHost preview, improved dashboard with export/import [devblogs.m…rosoft.com]. MAUI Avalonia Preview 1: Avalonia backend enables .NET MAUI apps on Linux & WebAssembly [avaloniaui.net]. Avalonia WebView goes open-source. Wolverine 5.25: Azure Service Bus topic/subscription interop with MassTransit/NServiceBus [gingter.org]. Marten 8.27: sharded multi-tenancy with database pooling [gingter.org]. MCP C# SDK v1.0 released officially [weekref.net]. .NET Skills repo launched for coding agent workflows [weekref.net], [devblogs.m…rosoft.com].
Community Content & Blogs March 2026 Kevin Gosse published Parts 8 (interior pointers) & 9 (frozen segments, allocation strategy) of “Writing a .NET GC in C#” [minidump.net]. Nick Cosentino released guides on C# design patterns and Semantic Kernel AI agents [morningdew…bsites.net]. Anthony Giretti detailed System.Text.Json improvements in .NET 10 [morningdew…bsites.net]. JetBrains’ dotInsights March 2026 roundup curated community links. The .NET Blog published “Modernize .NET Anywhere with GitHub Copilot” and “Extend your coding agent with .NET Skills” [devblogs.m…rosoft.com].
Community News & Events March 2026 Visual Studio Live! Las Vegas (Mar 16–20) at Planet Hollywood offered .NET 10 / Azure / AI training sessions. The inaugural Aspire Conf (Mar 23, virtual) celebrated the Aspire 13.2 launch with live demos [devblogs.m…rosoft.com]. The .NET Foundation opened 2025–2026 Board of Directors elections with 12 candidates, following Glenn Watson’s resignation (effective Feb 17, announced Mar 3) [dotnetfoundation.org], [dotnetfoundation.org]. Microsoft Build 2026 (June 2–3) registrations continue [weekref.net].

Table: March 2026’s key .NET updates and highlights by category (official releases, tooling, ecosystem, community).

Visualization

[blog.jetbrains.com], [devblogs.m…rosoft.com], [devblogs.m…rosoft.com], [htek.dev], [devblogs.m…rosoft.com], [avaloniaui.net], [devblogs.m…rosoft.com], [gingter.org], [blog.jetbrains.com]

Official Releases: .NET 11 Takes Shape, .NET 10 Stays Resilient

.NET 11 Preview 2

On March 10, Microsoft released the second preview of .NET 11, advancing the next annual .NET release across virtually every component. [devblogs.m…rosoft.com]

Runtime. Preview 2 continues building on Runtime Async (V2) — the project that moves async machinery into the runtime itself — alongside JIT improvements, cached interface dispatch, and other VM enhancements. Sebastian Gingter’s analysis notes these are not incremental fixes: “bounds check elimination, redundant checked-context removal, new Arm SVE2 intrinsics” all round out the runtime story “meaningfully”. [devblogs.m…rosoft.com] [gingter.org]

ASP.NET Core & Blazor. The headline feature is native OpenTelemetry tracing: ASP.NET Core now adds OTel semantic convention attributes to HTTP server activities directly, eliminating the need for the separate OpenTelemetry.Instrumentation.AspNetCore library. TempData support for Blazor SSR closes a gap in the POST-Redirect-GET pattern. A new .NET Web Worker project template enables offloading heavy computations to a Web Worker in Blazor WebAssembly apps, keeping the UI thread responsive. Additionally, Kestrel’s HTTP/1.1 parser now uses a non-throwing code path for malformed requests (port scans, misconfigured clients), delivering 20–40% throughput improvement in those high-invalid-traffic scenarios. OpenAPI 3.2.0 support was also added. [devblogs.m…rosoft.com], [infoq.com] [devblogs.m…rosoft.com], [gingter.org] [gingter.org], [infoq.com] [devblogs.m…rosoft.com]

Entity Framework Core. EF Core 11 gained LINQ translation for MaxBy and MinBy, replacing the verbose OrderByDescending(...).First() workaround. More strategically, support for SQL Server DiskANN vector indexes and VECTOR_SEARCH() arrived, enabling semantic search and RAG-style retrieval directly within an existing SQL Server + EF Core stack — lowering the barrier for teams evaluating whether vector search belongs in their architecture. Support for SQL Server full-text catalogs and indexes and JSON_CONTAINS() also shipped. [devblogs.m…rosoft.com] [gingter.org]

Libraries & SDK. A generic GetTypeInfo for System.Text.Json, tar archive format selection, and a ~15% faster Matrix4x4.GetDeterminant demonstrate continued attention to detail in the base class libraries. SDK container images are up to 17% smaller, and SDK installers on Linux and macOS were also reduced in size. [devblogs.m…rosoft.com], [infoq.com] [devblogs.m…rosoft.com]

.NET MAUI. The Map control received significant attention: XAML-defined coordinates, IsVisible and ZIndex properties for map elements, and click event support on Android and iOS. Binding performance improved substantially: TypedBinding and SourceGeneratedBinding are approximately 29% faster with 50% less memory allocation per operation, thanks to delegate caching and removal of unnecessary conversions. [infoq.com]

F#. The #elif preprocessor directive eliminates deeply nested conditional compilation blocks. A partitionWith function across core collection types allows splitting collections into two groups of different element types. All 462 functions across core collection modules now include Big-O complexity notes visible in IDE tooltips. An overload resolution caching mechanism reduces type-checking time from 6.5 seconds to 2.9 seconds in tested benchmarks. [devblogs.m…rosoft.com] [infoq.com]

C# 15 Union Types. While the official Preview 2 release notes stated no notable new C# language features shipped in the preview, the .NET Blog separately announced union types for C# 15 during March — allowing developers to declare a closed set of case types with implicit conversions and compiler-enforced exhaustive switch expressions. The syntax is concise (public union Pet(Cat, Dog, Bird);), and the compiler will not allow forgetting a case in pattern matching. This is a preview feature — not all specification items are implemented yet — but it signals a significant evolution in C#’s type system that the community had been requesting for years. [devblogs.m…rosoft.com] [devblogs.m…rosoft.com] [gingter.org]

.NET 10 Servicing: Three CVEs and an Emergency Patch

On March 10 (“Patch Tuesday”), Microsoft released .NET 10.0.4 alongside .NET 9.0.14 and .NET 8.0.25. The update addressed three security vulnerabilities — all classified as “.NET Security Feature Bypass Vulnerability”: [devblogs.m…rosoft.com]

CVE Applies to
CVE-2026-26130 .NET 10.0, .NET 9.0, .NET 8.0
CVE-2026-26127 .NET 10.0, .NET 9.0
CVE-2026-26131 .NET 10.0 only

Source: .NET and .NET Framework March 2026 servicing releases updates. [devblogs.m…rosoft.com]

Changelogs covered ASP.NET Core, Entity Framework Core, Runtime, and WPF components for .NET 10.0.4. .NET Framework had no new updates this month. [devblogs.m…rosoft.com]

Two days later, on March 12, Microsoft issued .NET 10.0.5 as an out-of-band emergency release. The cause: .NET 10.0.4 introduced a regression causing the debugger to crash when debugging applications on macOS using Visual Studio Code, particularly on Apple Silicon/ARM64 Macs. This regression was unrelated to the security fixes in 10.0.4. The fix specifically affected macOS users with VS Code who had installed .NET SDK 10.0.104, 10.0.200, or .NET 10.0.4 runtime; other platforms were not affected. The two-day turnaround from regression to fix exemplifies the team’s commitment to runtime reliability. [devblogs.m…rosoft.com] [gingter.org]

For .NET 10 users in production, the correct sequence was: apply 10.0.4 for the security fixes, then immediately update to 10.0.5 to resolve the debugger regression. [gingter.org]

Tooling Updates: Custom AI Agents, Smarter Debugging, and Multi-Editor .NET Support

Visual Studio 2026 v18.4

Visual Studio 2026’s March update (v18.4.0) — released March 10 — represented the most significant Copilot extensibility update since VS 2026’s launch. [htek.dev]

Custom Copilot Agents. Developers can now define specialized Copilot agents as .agent.md files inside .github/agents/ in their repositories. These agents receive full workspace awareness, code understanding, tool access, preferred model selection, and MCP connections to external knowledge sources like internal documentation, design systems, or databases. This moves Copilot from a general assistant toward team-customized, context-specific automation — from PR reviewers wired to Architecture Decision Records to design-system enforcers querying Figma. [devblogs.m…rosoft.com] [htek.dev]

Enterprise MCP Governance. For organizations, MCP server usage now respects allowlist policies set through GitHub. Administrators specify which MCP servers are permitted; unauthorized connections produce an error with no exceptions. This closes a governance gap for teams connecting agents to internal knowledge bases. [devblogs.m…rosoft.com]

Agent Skills. Reusable instruction sets (stored as SKILL.md files in .github/skills/ or ~/.copilot/skills/) teach agents how to perform specific tasks and are discovered automatically by Copilot. [devblogs.m…rosoft.com]

Debugging & Profiling. A “Profile with Copilot” command in Test Explorer profiles a selected test automatically, combining CPU and instrumentation data to deliver actionable insights. PerfTips powered by live profiling surface execution time, CPU usage, and memory behavior inline during debugging — click a slow line and Copilot suggests optimizations on the spot. Smart Watch Suggestions offer context-aware expression suggestions in Watch windows during debugging. [devblogs.m…rosoft.com] [htek.dev]

Additional improvements: a new find_symbol tool gives Copilot agents language-aware symbol navigation (all references, type metadata, scope) for C#, C++, Razor, TypeScript, and any LSP-supported language; Copilot can now fix NuGet vulnerabilities directly from Solution Explorer; the JSON editor ships with Core Editor by default (supporting JSON Schema Draft 2020-12 and 2019-09, up from Draft 4/7); and HTML rich copy/cut preserves syntax highlighting when pasting code into web apps or Azure DevOps work items. [devblogs.m…rosoft.com] [htek.dev]

Azure Developer CLI

The azd CLI shipped seven releases in March (versions 1.23.7 through 1.23.13), anchored by three themes: [devblogs.m…rosoft.com]

JetBrains Rider 2026.1

Rider 2026.1 went stable on March 30, delivering improvements across .NET development, game development, and the IDE experience. [blog.jetbrains.com]

ReSharper for VS Code

On March 5, JetBrains officially released the ReSharper extension for Visual Studio Code and compatible editors (Cursor, Google Antigravity, Windsurf, and others via OpenVSX). After a year in Public Preview, the extension brings JetBrains’ C# code analysis, quick-fixes, refactoring, and formatting to lightweight editor workflows — covering C#, Razor, Blazor, and XAML. It includes a Solution Explorer, unit test runner (NUnit, xUnit.net, MSTest), and fast navigation with external/decompiled source support. ReSharper also positions itself as a tool for refining AI-generated code — reviewing Copilot or Cursor output against professional standards before shipping. The extension is free for non-commercial use (learning, hobby, open-source), with commercial licenses under ReSharper, dotUltimate, or All Products Pack subscriptions. The next major focus area is debugging support (launching sessions and attaching to processes in .NET and .NET Framework apps). [blog.jetbrains.com] [blog.jetbrains.com], [blog.jetbrains.com]

Ecosystem News: Aspire Goes Agent-Native, Avalonia Brings MAUI to Linux

.NET Aspire 13.2

.NET Aspire 13.2 — released March 23 at the inaugural Aspire Conf — was described by the team as their “biggest release ever,” with over 1,100 closed issues. [gingter.org], [devblogs.m…rosoft.com]

The clearest theme: Aspire is now deliberately built for AI coding agents, not just developers. [gingter.org]

AI-Agent-Native CLI. The expanded CLI (aspire start, aspire stop, aspire ps, aspire doctor, aspire wait, aspire export, aspire secret, aspire docs) represents actions an agent may need to perform without human intervention: start an environment, wait for dependencies to stabilize, check health, grab debug snapshots, manage secrets. The --isolated flag lets agents spin up parallel environments on separate ports without collisions across git worktrees. The aspire docs command brings aspire.dev documentation directly into agent workflows for programmatic search and retrieval. [devblogs.m…rosoft.com], [gingter.org] [devblogs.m…rosoft.com]

TypeScript AppHost. The most-requested feature since Aspire 13 shipped as a preview: developers can now write their Aspire AppHost in TypeScript with the same orchestration model — resources, references, endpoints, startup dependencies — while the dashboard, service discovery, and health checks work identically to C# AppHosts. The .NET SDK is only required if the resource graph includes .NET projects. This multi-language foundation is designed to be repeatable, with more languages planned. [devblogs.m…rosoft.com]

Dashboard & Integrations. The dashboard now supports export/import of traces, spans, logs, and resource configurations as JSON or .env, plus an improved GenAI visualizer, OTLP/JSON support alongside gRPC, and query string value masking for sensitive data. New integrations include Certbot, overhauled Microsoft Foundry integration, and Bun support for JavaScript resources. [devblogs.m…rosoft.com]

Avalonia UI: MAUI Backend and Open-Source WebView

The Avalonia UI team delivered two significant announcements in March.

MAUI Avalonia Preview 1 (March 16) introduced an Avalonia backend for .NET MAUI, enabling MAUI apps to deploy to Linux and WebAssembly — platforms previously unsupported by MAUI’s native renderers. The setup is straightforward: add the Avalonia.Controls.Maui.Desktop NuGet, target net11.0, and add UseAvaloniaApp to the MauiBuilder. The team validated the approach by porting existing MAUI apps (MauiPlanets, 2048, the MAUI control gallery, AlohaAI, MyConference, WeatherTwentyOne) — “largely without changes” beyond trimming fixes and theme support. For developers choosing between native and drawn UIs, this gives MAUI users consistent cross-platform appearance via Avalonia while preserving the option of native platform controls where desired. A bespoke implementation of Maui.Essentials built on Avalonia is underway, and WinUI interoperability is planned to complete the native platform story. [avaloniaui.net]

Separately, on March 11, Avalonia announced it is open-sourcing the WebView control as part of Avalonia 12. Previously a proprietary component, the open-source WebView enables community improvements to web embedding across platforms — a move reflected in the WeatherTwentyOne MAUI port, which uses the newly open-sourced WebView on Linux and WebAssembly. [avaloniaui.net]

Open-Source Libraries and Official SDKs

Wolverine 5.25 (JasperFx) added Azure Service Bus topic and subscription interop for MassTransit and NServiceBus — directly reducing integration pain for teams operating in mixed messaging environments or migrating between transport frameworks. [gingter.org]

Marten 8.27 introduced sharded multi-tenancy with database pooling, providing first-class support for a complex PostgreSQL pattern that previously required significant custom implementation. [gingter.org]

The .NET Blog announced the v1.0 release of the official MCP C# SDK, providing a stable foundation for connecting .NET applications to Model-Context Protocol servers. Alongside this, the dotnet/skills repository launched as a collection of skills to assist AI coding agents with .NET and C# development workflows — part of a broader push to make the .NET ecosystem “agent-ready.” [weekref.net] [weekref.net], [devblogs.m…rosoft.com]

Additional notable releases tracked by WeekRef.NET during March include: Npgsql v10.0.2, v8.0.9, and v9.0.5; StackExchange.Redis 2.12.1; Swashbuckle.AspNetCore v10.1.5; Windows App SDK v1.7.9; Azure Cosmos DB .NET SDK 3.55.1; and Datadog .NET tracer v3.39.0. The WinUI Gallery 2.8 was also announced, and Microsoft.Data.SqlClient 7.0 Preview made Azure.Identity optional. [weekref.net]

On the game development side, Unity published a CoreCLR, Scripting, and ECS Status Update for March 2026, tracking progress on .NET modernization within the Unity engine. [weekref.net]

Community Highlights: Deep Technical Content and Developer Connection

Content & Blogs

March produced a rich body of community-driven technical content.

Kevin Gosse (JetBrains) continued the acclaimed series “Writing a .NET Garbage Collector in C#” with two new installments: Part 8 (March 3) on interior pointers and the brick table concept, and Part 9 (March 17) on frozen segments and a revised allocation strategy — pushing the boundaries of what NativeAOT and managed code can achieve at the runtime level. [minidump.net]

Nick Cosentino published a stream of practical C# guides, including implementations of the Factory Method and Builder design patterns and complete guides to integrating Semantic Kernel Agents and Semantic Kernel Plugins in C# — helping developers navigate Microsoft’s AI agent toolkit with concrete examples. [morningdew…bsites.net]

Anthony Giretti detailed System.Text.Json improvements in .NET 10 — specifically, duplicate property rejection (AllowDuplicateProperties = false) and direct PipeReader integration for high-performance JSON deserialization. [anthonygiretti.com]

Official .NET Blog posts during March included “Modernize .NET Anywhere with GitHub Copilot” (introducing the modernize-dotnet agent for assessing and upgrading .NET projects from VS, VS Code, CLI, or GitHub) and “Extend your coding agent with .NET Skills” (the dotnet/skills repository for agent workflow enhancement). JetBrains’ **dotInsights March 2026** curated community links across performance, AI, and .NET internals topics. [devblogs.m…rosoft.com]

News & Events

Visual Studio Live! Las Vegas (March 16–20) brought developers together at Planet Hollywood for hands-on sessions covering .NET 10, Azure, AI-assisted development, and cloud-native architecture.

Aspire Conf (March 23, virtual) served as the launch event for Aspire 13.2, featuring keynote demos and sessions on building distributed apps with AI coding agents — the first conference dedicated entirely to .NET Aspire. [devblogs.m…rosoft.com]

The .NET Foundation announced the 2025–2026 Board of Directors elections, presenting 12 candidates for community voting: Peter Smulovics, Jonathan “J.” Tower, Savino Carlone, Dr. Durgesh Singh, Divyesh Govardhanan, Chris Pulman, Joshua Arzt, Irina Dominte (Scurtu), Peter Ritchie, Vladislav Antonyuk, Aneesh Gopalakrishnann, and Ali Kolahdoozan. The election followed the announced resignation of Glenn Watson from the Board (effective February 17, 2026; published March 3), making the incoming directors’ contributions particularly significant for the Foundation’s continuity. [dotnetfoundation.org] [dotnetfoundation.org]

Looking ahead, Microsoft Build 2026 (June 2–3, San Francisco and online) continues accepting registrations, promising deep dives into .NET’s roadmap and AI strategy. With .NET 11 previews picking up cadence, C# 15 union types generating community discussion, and Aspire establishing itself as a first-class cloud-native framework, March set a strong trajectory for the rest of 2026. [weekref.net]

Visualization

[devblogs.m…rosoft.com], [gingter.org], [dotnetfoundation.org]