The .NET Insider - Issue 30

A faster, lighter C# Dev Kit · Drew Noakes
Version 11.0 rebuilds the extension as one Native AOT process with cached project loading. In Microsoft's benchmark on the 407-project Aspire repo, full solution load drops from 84 s to 3 s and memory from about 2 GB to 316 MB; it's in pre-release for now.

Aspire 13.6: Your dashboard gets memory · Maddy Montaquila
The dashboard now keeps traces, logs and resource state after you stop the AppHost (up to 10 runs, stored locally in SQLite). You can go back to the run where a bug showed up, and the new opt-in WithRepl() opens a signed-in database shell right in the dashboard.

Microsoft is updating its NuGet author-signing certificate · NuGet Team
Microsoft has started signing its NuGet packages with a new author certificate. If you enforce trusted signers or run dotnet nuget verify with Microsoft fingerprints, installs fail with NU3034 until you add it: dotnet nuget trust author Microsoft 9A1B131BEE0605433056A4EA3815478A8E177961A968C6C0027C1093D1FEB630 --algorithm SHA256

AG-UI Protocol now has a first-class .NET SDK · Daniel Roth
Microsoft and CopilotKit released an MIT-licensed .NET SDK for AG-UI, the open protocol for streaming agent events to user-facing apps. Any .NET service can now expose (AGUI.Server) or consume (AGUI.Client) agent endpoints that work with TypeScript and Python clients; Agent Framework users get a few renamed APIs, such as MapAGUIServer.

Build Agentic UI with the new Blazor AI components · Daniel Roth
The experimental Microsoft.AspNetCore.Components.AI package renders streamed agent output, tool calls, approval prompts and shared state as Blazor components. It gives .NET a ready-made UI layer for agents on top of any IChatClient; try it with the .NET 11 RC1 SDK and the AgenticUI sample.

Visual Studio September Update · Mark Downie
Bring Your Own Model (preview) now runs on the new Agent (Preview), with Foundry, OpenAI, Anthropic and Ollama. You can use your team's approved models in Visual Studio, but the old BYOM flow is gone and Ollama models need re-adding; the update also brings Copilot fixes for NuGet Audit warnings and Podman attach.

UWP and WinUI 3 apps: UI testing with MSTest · Amaury Levé
MSTest 4.5 can run UWP and WinUI 3 tests on the app's real UI dispatcher, across packaged, unpackaged and AppContainer hosts. UI tests no longer need workarounds for thread access; packaged hosts need Developer Mode, so check your CI agent first.

Experimental support for Device Bound Session Credentials (DBSC) in ASP.NET Core · Andrew Lock
.NET 11 adds experimental DBSC support to ASP.NET Core with one call, AddDeviceBoundSession(...). It ties a login session to a key in the device's TPM, so a stolen auth cookie stops working quickly; the package stays experimental after .NET 11 ships.

File-based apps can reference other C# files · Denis Makarenko
The new #:ref directive lets a dotnet run app.cs program pull in a second C# file. File-based apps can now grow past one file without a project, though on .NET 11 RC1 it's still behind an experimental property.

What's Inside That Bearer Token? A Practical Guide to Encrypted JWTs (JWE) in .NET · Robert Dennyson
A walkthrough of spotting, inspecting and decrypting encrypted JWTs with JsonWebTokenHandler. Useful when you debug auth: decryption and validation are separate steps, and any token pasted into a chat or log should be treated as exposed.

How to Make AI Write High-Quality Code in .NET · Anton Martyniuk
Rules written in prompts fade as an AI agent's context fills up, so the article moves them into the build with TreatWarningsAsErrors, analyzers, .editorconfig and Central Package Management. The agent then sees and fixes violations itself, before you ever review the diff.

Stripping extra dependencies in .NET NativeAOT apps using linker substitutions · Andrew Lock
An ILLink.Substitutions.xml file turns a runtime check into a constant, so the linker can remove code it couldn't prove was unused. In Andrew's case that dropped a chain of Azure identity dependencies and cut a NativeAOT binary by 22 to 25 percent.