📅 Daily .NET News Update — February 15, 2026

🚀 Top Story: .NET 11 Preview 1 Arrives with WASM Overhaul

Microsoft has officially kicked off the 2026 release cycle with the launch of .NET 11 Preview 1. This version is designated as a Standard Term Support (STS) release, meaning it will receive two years of support following its general availability this November.

• CoreCLR on WebAssembly: In a major architectural shift, the .NET WebAssembly SDK is migrating from the Mono runtime to CoreCLR. This change brings JIT (Just-In-Time) performance to the browser and improves debugging capabilities for Blazor applications.
• Android Performance: CoreCLR is now the default runtime for Android Release builds, a significant move to improve startup times and overall compatibility with the broader .NET ecosystem.
• Native Zstandard Support: A new ZstandardStream class has been added to System.IO.Compression, providing significantly faster compression and decompression than older algorithms like GZip.

🔧 C# 15 & Tooling Innovations

• Collection Expression Arguments: C# 15 introduces the with() element, allowing you to pass constructor arguments—such as initial capacity or custom comparers—directly inside the collection expression brackets [].
• Interactive CLI Selection: The dotnet run command has been enhanced to support interactive selection workflows. If a project has multiple target frameworks or devices, the CLI will now prompt you to select one using your arrow keys.
• Visual Studio 2026 GA: Visual Studio 2026 is now generally available. Key features include Compact spacing in Solution Explorer to reduce vertical padding and Fast scrolling by holding the Alt key while using the mouse wheel.

🛡️ Security: Patch Tuesday Servicing Rollup

The February 10 servicing releases are now available for all supported versions of .NET.

• Critical Vulnerability: Updates for .NET 10.0.3, .NET 9.0.13, and .NET 8.0.24 address CVE-2026-21218, a security feature bypass vulnerability.
• NTLM Retirement: Security recommendations have been updated to encourage disabling NTLM authentication on Windows workstations to prevent credential theft and lateral movement attacks.
• M365 Agents Toolkit: New templates have been added to Visual Studio for building Teams Collaborator Agents and Travel Agents, utilizing the latest Microsoft 365 Retrieval APIs.

📢 Community & Ecosystem Spotlight

• "Syntax Bloat" Debate: The new C# 15 collection expression arguments have sparked a lively debate, with some developers praising the power and others expressing concerns about increasing language complexity.
• The AI Pivot: Microsoft is heavily promoting "Agentic AI" for .NET 11, focusing on support for the Model Context Protocol (MCP) to allow .NET apps to function as tools for AI agents.
• F# 11 Enhancements: The F# compiler now has parallel compilation enabled by default and offers faster compilation for computation expression-heavy code.

💡 Tip of the Day: Setting HashSet Case-Insensitivity

In C# 15, you can now create a case-insensitive HashSet in one line using the new collection expression syntax:

// C# 15 Syntax
HashSet<string> set = [with(StringComparer.OrdinalIgnoreCase), "Hello", "HELLO"];
// set will contain only 1 element.