The .NET Insider - Issue 32

.NET October 2026 Out-of-Band Security Updates · Rahul Bhandari

Microsoft has released .NET 8.0.33, 9.0.22, 10.0.14, and .NET 11 RC3 with security fixes for Brotli decompression and Linux tarball ownership, plus completed fixes from the earlier October release. Update framework-dependent runtimes and restart applications; rebuild and republish self-contained apps and containers. RC2 users should move to RC3.

Microsoft.UI.Reactor: a C#-first way to build WinUI apps · Alexandre Zollinger Chohfi

Microsoft’s experimental framework brings Model-View-Update to WinUI, describing interfaces in C# and updating native controls as state changes. The walkthrough includes a counter built as a .NET 10 file-based app. Reactor has no support policy or API guarantees yet; it offers another way to build WinUI interfaces alongside XAML and MVVM.

Memory-efficient JSON in .NET 10 web APIs with PipeReader · Ali Hamza Ansari

A walkthrough comparing stream-based JSON deserialization with .NET 10’s PipeReader support in System.Text.Json, using a payload containing one million readings. The example measures execution time, allocations and garbage collections. Useful for exploring large-payload processing, with results to validate against your own application’s workload.

Are Async Database Inserts Really Faster in .NET? · David McCarter

A benchmark-focused comparison of synchronous and asynchronous database inserts, asking when each approach makes sense. The public preview challenges the assumption that async always finishes faster. Useful as a prompt to measure your own database workload rather than choosing an execution model from its name alone. Paid subscription required.

Stop Blocking on the Database Inside IsValid: .NET 11 Validates Async · JKC

A walkthrough of asynchronous DataAnnotations validation with AsyncValidationAttribute, IAsyncValidatableObject and the async Validator APIs. Examples move database-backed checks away from blocking calls inside IsValid. The article also covers cancellation, validation stages and the validateAllProperties flag, including why synchronous validation paths need deliberate handling.

.NET tasks AI is better at than developers · David Grace

David demonstrates using Claude Code for project creation, unit tests, comments and exception debugging in an ASP.NET Core Web API. Reusable Markdown specifications define the architecture, packages, coding conventions and verification steps. The practical focus is the preparation behind the prompts: explicit requirements give the agent a clearer implementation target.

Compare today’s code with an earlier commit · Leah Tran

Visual Studio 2026 version 18.11 adds Compare with Working Tree to the repository’s commit workflow. Select a historical commit to inspect how your current files differ, including uncommitted changes, without switching branches. The comparison lists every differing file, rather than only files modified by the selected commit.

Organize and revisit tabs with the keyboard · Mads Kristensen

Visual Studio 2026 version 18.11 adds shortcuts to arrange the active tab and return to documents by position. Ctrl+Shift+PgUp/PgDn moves a tab, while Ctrl+NumPad1 through NumPad9 selects a visible tab in the active group. Pinned sections and project groups still apply; preview tabs cannot be moved.

Keep your investigation between sessions · Jason Chlus and Mads Kristensen

Create a standalone Markdown note through New File, then use Visual Studio 2026 version 18.11’s opt-in Hot Exit preview to restore unfinished notes and unsaved edits after reopening the IDE. It preserves investigation context without requiring a project item. Save the document when you want to share it or keep it in the repository.

JetBrains .NET Day Online 2026: Watch the Recordings · Mehul Harry

The October 7 event’s sessions are available on YouTube, covering agent workflows in Rider, Outbox/Inbox/Saga messaging patterns, C# interceptors and Native AOT, and NuGet supply-chain attacks. The recap explains each session so you can choose a topic without watching the whole event.

JetBrains GameDev Day 2026: Watch the Recordings · Anna Ruban

Catch up on September’s event with sessions on Unreal Engine profiling, Unity UI automation, procedural generation in Godot and debugging across C# and C++. Other talks cover version control for game assets and evolving a live engine. The recap groups recordings by engine and role to help you choose where to start.

C# Concepts Every .NET Backend Developer Should Know in 2026 · qodors

A backend fundamentals refresher that starts with interfaces, asynchronous I/O and EF Core query optimization. Examples show the cost of blocking HTTP calls and loading more database data than an endpoint needs. A practical review for developers connecting language features with maintainability, testing and application behavior under load.

This week in Cursor + .NET — 7 rules · Agentic Architect

Seven opinionated rules for reviewing agent-generated C#: value objects versus entities, sealed classes, strongly typed IDs, typed configuration, exception rethrowing, query tracking and dependency-injection lifetimes. Treat the list as a starting point for project-specific instructions, with particular attention to singleton services capturing scoped dependencies.

Azure DevOps Comes to Microsoft Copilot with Plugin for Work Items, Pull Requests · David Ramel

An overview of the Azure DevOps plugin for Microsoft Copilot, with access to work items, pull requests, pipelines, and test plans. Microsoft’s announcement shows how to use Cowork to turn requirements into structured backlogs and connect meeting notes to work items. Check that your organization has access to the required Copilot experience; Azure DevOps Server is not supported.