Browse .NET News (86)

Dmitrii Korolev explains how C# 15 union types and closed class hierarchies behave in ASP.NET Core when serialized with System.Text.Json, including what works in Minimal APIs, MVC, SignalR, Blazor, and OpenAPI, plus the trade-offs around discriminator-free JSON and ambiguous payloads.

Allison announces CodeQL 2.27.0, highlighting native Linux ARM64 support, improvements to GitHub code scanning default setup, and multiple query and framework-modeling updates that improve vulnerability detection across C#, Java/Kotlin, C/C++, and Rust projects.

.NET Team announces .NET 11 Release Candidate 1, highlighting runtime, SDK, MSBuild, NuGet, and language updates, plus ASP.NET Core, .NET MAUI, and Windows Forms improvements. The post links to detailed release notes and includes download and tooling guidance for trying RC1 in production.

Javier Lozano, Chris Sfanos, and Jon Galloway announce that the call for presenters is open for .NET Conf 2026 Community Days, with session proposals accepted from September 8 through October 6, 2026, and a separate volunteer opportunity for helping run the event.

Rahul Bhandari and Tara Overfield recap the September 2026 servicing releases for .NET and .NET Framework, highlighting security and non-security fixes, the list of addressed CVEs, and where to find release notes, installers, container images, Linux packages, and known issues for supported versions.

Justin Yoo walks through a practical profiling workflow for distributed .NET apps, showing how to identify which process owns a slow user interaction, use Visual Studio CPU profiling to rule out CPU-bound work, and then measure hidden async waiting that doesn’t show up in CPU samples.

Justin Bettencourt’s August 2026 Azure SDK roundup highlights new and updated client libraries across .NET, Java, JavaScript/TypeScript, Python, Go, and more, including Document Translation 2.0.0, Azure Storage Blobs 12.30.0-beta.1, and the first stable release of Azure AI Discovery.

Amaury Levé explains how MSTest 4.4 uses source generation to make test projects publishable and runnable as Native AOT executables, so your tests exercise the same trimming and reflection constraints as the app you deploy.

Allison summarizes what’s new in CodeQL 2.26.4 for GitHub code scanning, including language support updates and query accuracy improvements that affect security detections across C#, Java/Kotlin, and GitHub Actions workflows.

The Visual Studio Code Team shares Insiders updates for VS Code 1.137, focusing on Copilot-related workflow improvements such as clearer model token limits, better context handling when pasting GitHub issue/PR links, and updated new-session composer controls.

Mads Kristensen shows how to give each Visual Studio solution its own color theme so multiple IDE instances are easier to tell apart. He also explains the new scoped settings model in Visual Studio 2026, where solution-level settings are stored in a JSON file you can optionally commit to source control for consistent team setup.

Aaron Powell walks through reviewing GitHub pull requests directly inside Visual Studio, from opening the PR list and navigating diffs to leaving inline comments, approving, and merging. He also shows how to bring GitHub Copilot into the review by adding a PR as chat context using the UI or the #pullrequest: command.

Allison summarizes the August 2026 update for GitHub Copilot in Visual Studio, including organization-level custom agents, usage visibility, model selection and “thinking effort” controls, and a Git agent that can review uncommitted changes or commits before opening a pull request.

Allison summarizes the August 24 weekly GitHub Copilot updates, covering shared agent sessions in Slack and Microsoft Teams, the Copilot app’s new Customize experience (including MCP servers and plugins), Copilot CLI session and permission defaults, and IDE improvements across VS Code, JetBrains, and Visual Studio.

Sam Basu explains how Uno Platform built two MCP servers in C#—one for documentation grounding and one for driving a live app—so AI agents can look up accurate APIs, run and inspect a cross-platform .NET UI, and validate changes instead of just generating code.

Wes Steyn shows how to take a Microsoft Agent Framework “claw” from a working local prototype to something you can actually run for other people: one shared agent factory feeding multiple hosts, with OpenTelemetry observability, Purview governance, Foundry hosting, and repeatable evals for quality and regression checks.

James Rempt recaps VSLive! @ Microsoft HQ 2026 with the main themes developers discussed—AI across the workflow, GitHub Copilot inside Visual Studio, and practical .NET modernization—and links to recorded sessions on performance, ASP.NET Core/Blazor, C#, and an MCP-based SQL agent scenario.

Harshada Hole introduces a new Test-Driven Investigation workflow for the Visual Studio Debugger Agent, aimed at making hard-to-reproduce bugs repeatable by capturing them in an automated test and then using that test to drive debugging, validate the fix, and check for regressions.

The Visual Studio Code Team shares a small update for the VS Code 1.136 Insiders release notes, highlighting a UI change in VS Code Chat where the Artifacts pill icon now uses a package symbol to better represent generated outputs from the current session.

Jon Galloway announces .NET Conf 2026 (Nov 10–12), a free online event aligned with the .NET 11 launch, and points readers to current previews and related deep dives across the runtime, SDK, ASP.NET Core, Blazor, MAUI, and C# 15.

Mark Downie highlights the Visual Studio August update, focusing on new GitHub Copilot controls (model “thinking effort”, org-wide custom agents, and in-IDE usage visibility) plus Git tooling improvements that make it easier to work across multiple branches and repositories.

Tanmayee Kamath announces a preview of Bring Your Own Model (BYOM) in Visual Studio 18.10 Insiders, letting developers connect Visual Studio’s Agent mode to Microsoft Foundry/Azure AI Foundry deployments or other supported model providers, including custom endpoints for OpenAI and Ollama.

Bruno Capuano shows how to take a minimal Microsoft Agent Framework console app and deploy it as a Foundry Hosted Agent in Azure using one prerelease NuGet package, three lines of C#, and two azd commands—while getting managed identity, session state, observability, and an OpenAI-compatible /responses endpoint.

Bill Wagner introduces the C# 15 preview shipping with .NET 11 Preview 7, highlighting the biggest language changes and what they mean in real code: union types, closed hierarchies, a preview redesign of unsafe/memory-safety rules, plus updates to collection expressions, extension members, and loop control flow.

Matt Soucoup and Pablo Lopes walk through upgrading a legacy .NET Framework sample app to .NET 10 using the GitHub Copilot modernization experience built into Visual Studio, showing how guided checkpoints produce an assessment report, an upgrade plan, and step-by-step execution you can review and commit to source control.

The Visual Studio Code Team shares the VS Code 1.135 Insiders release notes page, with links to the commit log and closed issues for tracking progress as features land in the Insiders build.

Joshua Yue introduces new experimental routing and failover primitives in Microsoft.Extensions.AI, showing how .NET apps can route chat requests across multiple model/providers, do content-based semantic routing with embeddings, and fail over safely when a client fails—while keeping request options and streaming behavior predictable.

Lily Du explains how to build Microsoft Teams agents that participate in busy chats and channels without adding noise, using lightweight interaction patterns like emoji reactions, threaded replies, and quoted replies.

Wendy Breiding explains how to keep GitHub Copilot (and other frontier coding models) effective by treating repository instructions as a high-signal budget: document the local facts, constraints, and validation commands the model can’t infer, and remove vague “prompt folklore” that adds noise.

sbaynes announces MAI-Code-1.1-Flash, a new coding model now running in GitHub Copilot, focused on better code quality and lower cost. The post highlights token-efficiency gains, benchmark improvements in Copilot CLI and .NET tasks, and production metrics like code survival and return visits.

The .NET Team announces .NET 11 Preview 7 and highlights what’s new across the runtime, SDK, libraries, and app frameworks, with links to detailed release notes for C#, ASP.NET Core (including Blazor), .NET MAUI, EF Core, F#, and Windows Forms.

Rahul Bhandari and Tara Overfield recap the August 2026 servicing releases for .NET and .NET Framework, highlighting security and non-security fixes, the list of addressed CVEs, and where to find release notes, installers, container images, Linux packages, and known issues for supported .NET versions.

Harshada Hole introduces first-class Git submodule support in Visual Studio 18.9, showing how submodules now appear in the Git UI and how you can add, update, and remove them without switching to a terminal.

Amaury Levé explains how Microsoft.Testing.Platform (MTP) reporting helps teams move from a failing CI build to actionable evidence, with inline annotations in GitHub Actions and Azure DevOps, Azure DevOps-only history-based flaky/regression triage, crash-resilient TRX output, and multiple report formats for both humans and automation.

Mike Hulme explains why Microsoft was named a Leader in Gartner’s 2026 Magic Quadrant for AI-augmented code modernization tools, and outlines how GitHub Copilot modernization and Azure are positioned to assess, upgrade, and migrate legacy applications with agentic workflows while keeping developers in control.

The Visual Studio Code Team shares the 1.133 Insiders release notes, highlighting a change for extension authors: custom editor extensions can now set different default priorities for normal editing versus diff views, improving how custom editors behave when comparing files.

Bruno Capuano shows how to build a Windows-only C# console app that performs live speech-to-text locally using Foundry Local and a compact Nemotron streaming ASR model, including model lifecycle management (download/cache/load/unload) and real-time interim/final transcription via async streams.

Giles Odigwe announces the stable release of the GitHub Copilot Agent for Microsoft Agent Framework in .NET and Python, showing how to use Copilot’s coding harness (shell, file, URL, and MCP tools) with Agent Framework features like middleware, streaming, OpenTelemetry tracing, and human-in-the-loop approvals.

Allison summarizes the CodeQL 2.26.2 release for GitHub code scanning, including new language support (Swift 6.3.3 and Kotlin 2.4.10), query behavior changes that may surface more findings, and a breaking change affecting how query authors embed links in alert messages.

.NET Team announces upcoming NuGet.org publishing security changes: new API keys will be capped at 30 days starting August 17, 2026, and older keys will expire on November 1, 2026. The post explains the supply-chain risk of long-lived secrets and recommends migrating to NuGet Trusted Publishing using OIDC.