Tuesday, October 20, 2026 stories of the day

Stories

10 stories
Marten
Storing type hierarchies

Storing and Querying a Hierarchy of Types with Marten

Jeremy D. Miller shows how Marten stores a class hierarchy in one PostgreSQL table and queries it with LINQ, without the table-per-type or table-per-concrete-type decisions EF Core requires. He also covers subtype-specific partial indexes and duplicated fields. For teams weighing document storage against EF Core inheritance mapping, it is a useful comparison.

Foundry Agent
MCP in Foundry agents
BTTaiseer Joudeh (Bit of Tech) Taiseer Joudeh Oct 20

Connecting an MCP Server to Microsoft Foundry Agent Service

Part 9 of Taiseer Joudeh's MCP series shows how to attach an existing ASP.NET Core MCP server to a hosted Foundry agent without changing its code. The setup covers a Foundry project, an Entra app registration, a custom MCP connection using OAuth identity passthrough, and a toolbox. It matters for .NET teams that want the agent loop in Azure while user-based authorization still works.

Xcode 27 / .NET MAUI
Getting ready for Xcode 27
NB.NET Blog Gerald Versluis Oct 19

Prepare your .NET MAUI app for Xcode 27 with the UIKit scene lifecycle

iOS apps built with Xcode 27 must adopt the UIKit scene lifecycle, or they can vanish right after the splash screen. Microsoft explains an agent skill that prepares existing .NET MAUI projects, plus the manual steps for the scene delegate, Info.plist manifest and minimum OS versions. It also covers moving AppDelegate callbacks to scene events.

Copilot SDK 1.0
Bring your own model
NB.NET Blog Bruno Capuano Oct 19

Bring Your Own Model to the GitHub Copilot SDK with C#

The GitHub Copilot SDK lets you keep GitHub's agent runtime while routing model inference to your own Microsoft Foundry or Azure OpenAI deployment through BYOK. The article walks through a .NET 10 console sample that configures ProviderConfig, authenticates with Microsoft Entra ID or an API key, and sends one prompt.

Claude Code
C# in Claude Code

C# Code Intelligence in Claude Code: Setup and Limits

Nick Cosentino explains how to set up C# code intelligence in Claude Code through the csharp-lsp plugin and where that setup stops being reliable. The article separates the language server, the plugin and the workspace as three layers to verify, and it clarifies what diagnostics and symbol navigation can and cannot prove. It is a practical checklist for .NET developers using Claude Code on C# repositories.

MCP · ASP.NET Core
Your API as MCP tools
DVDEV Community: #aspnetcore Rahmat Afridi Oct 19

Exposing Existing ASP.NET Core APIs to AI Agents with a Secure MCP Server

A practical guide to adding a Model Context Protocol server to an existing ASP.NET Core app using the official ModelContextProtocol C# SDK. It covers wrapping existing services as read-only tools, locking the endpoint down with JWT authentication and per-tool authorization, and verifying the surface with an MCP client. Useful for teams that want AI agents to use their current APIs without a rewrite.

Graph + RAG
RAG over Microsoft Graph
DPdotnetpro (de) Dr. Veikko Krypczyk Oct 19

Building a RAG assistant with Microsoft Graph and .NET

Microsoft Graph supplies calendar, mail and document data that can be indexed with Azure AI Search and passed to a language model to produce sourced answers. The article walks through a .NET retrieval-augmented generation flow with code for loading context, chunking documents and calling the model. It stresses least-privilege scopes and permission-aware retrieval, which matter for any enterprise assistant.

ADFS + OIDC
Extra claims from ADFS

Using the ADFS userinfo endpoint instead of allatclaims

This post shows how to keep the ADFS ID token small and fetch extra claims from the OpenID Connect userinfo endpoint instead of using allatclaims. It covers the urn:microsoft:userinfo claim rules and the ASP.NET Core OpenIdConnect setting that merges those claims. It also flags the audience error that appears when the wrong token is sent.

Wolverine 6.51
Zero-downtime rebuilds
JXJasperFx (Critter Stack) Blog Jeremy Miller Oct 19

Rebuilding Marten Projections Without Downtime with Wolverine 6.51 Warm-up Nodes

Wolverine 6.51 adds a warm-up node role for blue/green deployments. New nodes join the cluster only to rebuild new projection versions in Marten or Polecat, without handling messages or subscriptions. Combined with versioned projections and a side-effect gate, teams can catch up read models before switching traffic. This is a practical path to zero-downtime releases for event-sourced systems.

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