--- title: .NET 11 Preview 6: what's new in C#, ASP.NET Core, MAUI,... description: Microsoft released .NET 11 Preview 6 with notable updates across C#, ASP.NET Core, .NET MAUI, and EF Core. C# gains extension indexers, ASP.NET Core adds async... canonical: https://daily.dev/posts/net-11-preview-6-what-s-new-in-c-asp-net-core-maui-ef-core-and-performance-mzxreivyq twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: .NET 11 Preview 6: what's new in C#, ASP.NET Core, MAUI, EF Core, and performance | daily.dev og:description: Microsoft released .NET 11 Preview 6 with notable updates across C#, ASP.NET Core, .NET MAUI, and EF Core. C# gains extension indexers, ASP.NET Core adds async... og:url: https://daily.dev/posts/net-11-preview-6-what-s-new-in-c-asp-net-core-maui-ef-core-and-performance-mzxreivyq og:image: https://api.daily.dev/og/posts/mzXreIvyq.png og:image:alt: .NET 11 Preview 6: what's new in C#, ASP.NET Core, MAUI, EF Core, and performance og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # .NET 11 Preview 6: what's new in C#, ASP.NET Core, MAUI, EF Core, and performance **[Collections](https://daily.dev/sources/collections)** · 3 min read · 11 upvotes · 0 comments ## Summary Microsoft released .NET 11 Preview 6 with notable updates across C#, ASP.NET Core, .NET MAUI, and EF Core. C# gains extension indexers, ASP.NET Core adds async validation, automatic CSRF protection, and OpenAPI 3.2 as default, while EF Core finally supports FULL OUTER JOIN translation. Benchmarks on Apple M2 Pro show meaningful performance gains: Enum.Equals is ~7x faster due to eliminated boxing, DateTime.Now timezone handling is ~2x faster, Guid.Parse is 20-25% faster, and LINQ Min/Max uses a SIMD shuffle-based reduction for up to 4x speedup on small arrays of narrow integer types. The Enum.Equals fix is considered the most broadly impactful change for everyday code. ## Content ## What's new in .NET 11 Preview 6 Microsoft shipped .NET 11 Preview 6 with changes across ASP.NET Core, C#, EF Core, and .NET MAUI. Here's what's worth paying attention to. --- ## New CSRF protection based on Fetch Metadata headers The most architecturally interesting change is a new CSRF protection mechanism in ASP.NET Core. Instead of the traditional synchronizer token pattern, the new approach uses [Fetch Metadata request headers](https://developer.mozilla.org/en-US/docs/Glossary/Fetch_metadata_request_header) — specifically `Sec-Fetch-Site`, `Sec-Fetch-Mode`, and related headers that browsers attach automatically. The old token-based approach had real operational costs: it depended on the Data Protection system, caused token invalidation when users had multiple tabs open, and added per-request cryptographic work. The new approach sidesteps all of that. The algorithm is straightforward: 1. Allow safe HTTP verbs (GET, HEAD, OPTIONS) through unconditionally. 2. Allow requests from the same origin. 3. Allow cross-origin requests if a CORS policy explicitly permits that origin. 4. Block everything else. A new `CsrfProtectionMiddleware` is added automatically when you use `WebApplicationBuilder`. Blazor SSR and minimal APIs benefit cleanly from this. MVC and Razor Pages are messier — they still generate and validate tokens on top of the new middleware, and opting out entirely requires some hacking. If you have legitimate cross-origin form posts, the right move is to configure CORS allowed origins rather than disabling CSRF protection wholesale. --- ## Other notable changes - **C# extension indexers** — new language feature for adding indexer syntax to existing types - **Async validation** in ASP.NET Core - **OpenAPI 3.2 by default** - **EF Core FULL OUTER JOIN translation** --- ## Measured performance improvements Someone ran BenchmarkDotNet comparisons between .NET 10 and .NET 11 preview on Apple M2 Pro. The headline numbers: - **`Enum.Equals`** — about 7x faster, zero allocations (previously caused boxing) - **Redundant span/null check elimination** — roughly 10% faster on vectorized sums - **`DateTime.Now` timezone handling** — about 2x faster - **`Guid.Parse`** — 20-25% faster - **LINQ `Min`/`Max`** — up to 4x faster for small `byte`/`short` arrays, using a SIMD shuffle-based reduction instead of scalar iteration The LINQ gains are the most interesting to me. The improvement is most pronounced on smaller integer types and smaller array sizes — which is exactly the kind of thing that's easy to overlook but shows up constantly in real code. Larger arrays and wider types see more modest gains. Results will vary depending on your workload, but the direction is consistently positive. ## Questions this post answers ### How does the new CSRF protection in .NET 11 differ from the old token-based approach in ASP.NET Core? ASP.NET Core in .NET 11 Preview 6 replaces the synchronizer token pattern with a CsrfProtectionMiddleware based on browser-sent Fetch Metadata headers like Sec-Fetch-Site and Sec-Fetch-Mode. It allows safe verbs (GET, HEAD, OPTIONS), same-origin requests, and CORS-approved cross-origin requests, blocking everything else, without relying on the Data Protection system or per-tab tokens. _Teams planning an ASP.NET Core upgrade can track CSRF and middleware changes like this on daily.dev._ ### How much faster is Guid.Parse in .NET 11 compared to .NET 10? Guid.Parse is roughly 20-25% faster in .NET 11 preview builds compared to .NET 10, based on BenchmarkDotNet comparisons run on an Apple M2 Pro. Other measured gains in the same tests include Enum.Equals running about 7x faster with zero allocations, DateTime.Now timezone handling about 2x faster, and LINQ Min/Max up to 4x faster on small byte and short arrays. _Developers benchmarking runtime upgrades can follow .NET performance changes like these on daily.dev._ ### Do MVC and Razor Pages still need CSRF tokens under the new Fetch Metadata based protection in ASP.NET Core? Yes, MVC and Razor Pages continue to generate and validate anti-forgery tokens on top of the new CsrfProtectionMiddleware in .NET 11 Preview 6, unlike Blazor SSR and minimal APIs which benefit cleanly from the new header-based approach alone. Fully opting out of token-based protection in MVC or Razor Pages requires extra manual configuration. _Developers migrating ASP.NET Core apps can weigh framework-specific CSRF tradeoffs like this via daily.dev._ ## Similar posts on daily.dev - [Microsoft Releases .NET 11 Preview 6 With Language and Framework Updates](https://daily.dev/posts/microsoft-releases-net-11-preview-6-with-language-and-framework-updates-oqwjdzv3l) · InfoQ · 6 upvotes · 0 comments - [.NET 11 Preview 2 Brings Performance Gains, Improved Mapping, and Native OpenTelemetry Support](https://daily.dev/posts/net-11-preview-2-brings-performance-gains-improved-mapping-and-native-opentelemetry-support-1t5uposcx) · InfoQ · 6 upvotes · 0 comments --- Tags: [#performance](https://daily.dev/tags/performance), [#.net](https://daily.dev/tags/.net), [#c#](https://daily.dev/tags/c#), [#aspnet](https://daily.dev/tags/aspnet) [View this post on daily.dev](https://daily.dev/posts/net-11-preview-6-what-s-new-in-c-asp-net-core-maui-ef-core-and-performance-mzxreivyq) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":".NET 11 Preview 6: what's new in C#, ASP.NET Core, MAUI, EF Core, and performance","url":"https://daily.dev/posts/net-11-preview-6-what-s-new-in-c-asp-net-core-maui-ef-core-and-performance-mzxreivyq","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/net-11-preview-6-what-s-new-in-c-asp-net-core-maui-ef-core-and-performance-mzxreivyq"},"datePublished":"2026-08-01T15:10:04.413Z","dateModified":"2026-09-13T19:42:26.235Z","description":"Microsoft released .NET 11 Preview 6 with notable updates across C#, ASP.NET Core, .NET MAUI, and EF Core. 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