--- title: .NET 11 Preview 7: what's new before the November release description: Microsoft released .NET 11 Preview 7, a substantial update ahead of the November general availability. Highlights include tiered compilation for async methods... canonical: https://daily.dev/posts/net-11-preview-7-what-s-new-before-the-november-release-qq7fnicrv twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: .NET 11 Preview 7: what's new before the November release | daily.dev og:description: Microsoft released .NET 11 Preview 7, a substantial update ahead of the November general availability. Highlights include tiered compilation for async methods... og:url: https://daily.dev/posts/net-11-preview-7-what-s-new-before-the-november-release-qq7fnicrv og:image: https://api.daily.dev/og/posts/Qq7FNIcRv.png og:image:alt: .NET 11 Preview 7: what's new before the November release 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 7: what's new before the November release **[Collections](https://daily.dev/sources/collections)** · 2 min read · 13 upvotes · 0 comments ## Summary Microsoft released .NET 11 Preview 7, a substantial update ahead of the November general availability. Highlights include tiered compilation for async methods with runtime-async tiering and tail-await optimizations, continued work running CoreCLR inside WebAssembly via a portable interpreter and R2R model, NativeAOT and MSBuild server enabled by default for the dotnet CLI, and new dotnet test options for run-level timeouts and max failed tests. The base class library adds IEEE 754 decimal floating-point types, a generic Complex type, and an HttpContent compression wrapper. C# 15 introduces labeled break/continue for nested loops. ## Content C# 15, previewed alongside .NET 11, is shaping up to be one of the more interesting language releases in a while. Two features stand out: a new `closed` keyword for exhaustive class hierarchies, and nominal union types. Both hit switch-expression exhaustiveness from different angles, and .NET 11 Preview 7 (released August 11, 2026) bundles them with a long list of other changes across ASP.NET Core, MAUI, EF Core, and Windows Forms. ## The `closed` keyword Today, if you write a switch expression over a class hierarchy, the compiler can't know you've covered every case unless you add a discard pattern (`_ => ...`). That's because any assembly could theoretically add a new derived type. Developers have worked around this for years with `internal` or `private protected` constructors, but it's a hack, not a real solution. The `closed` keyword lets you mark a base class or record as closed to derivation outside the declaring assembly. Once you do that, the compiler can verify a switch expression is exhaustive without a discard, and it warns immediately if someone adds a new derived class without updating the switch. There are some fiddly edge cases (deriving from a derived class, for instance) but the core idea is straightforward and, frankly, overdue., You can try it now in .NET 11 Preview 6 or later by setting `LangVersion` to `preview`. ## Union types: promising, but not what F# fans might hope for The other big exhaustiveness feature is nominal union types — an `IUnion`-backed struct that wraps a fixed set of existing types. It's easy to see this and think ## Questions this post answers ### What new async performance feature is in .NET 11 Preview 7? NET 11 Preview 7 adds tiered compilation for async methods along with runtime-async tiering and tail-await optimizations. Async code should compile and run more efficiently without any changes needed in existing projects. This is one of several runtime improvements alongside continued work on running CoreCLR inside WebAssembly using a portable interpreter and R2R model. _Track .NET 11's async runtime changes on daily.dev before rolling out the upgrade._ ### Is NativeAOT enabled by default in .NET 11? Yes, NativeAOT is now enabled by default for the dotnet CLI in .NET 11 Preview 7, and the MSBuild server is also on by default, which should speed up build times for many projects. This preview shipped ahead of the planned November general availability, following Preview 6 on July 14. _Developers planning .NET 11 upgrades follow build tooling changes like this on daily.dev._ ### What new options were added to dotnet test in .NET 11? dotnet test in .NET 11 Preview 7 gained a run-level timeout option and a maximum-failed-tests flag, letting developers stop a test run early instead of waiting for it to finish entirely. These join a broader set of runtime, C#, ASP.NET Core, MAUI, EF Core, and Windows Forms updates in this preview. _Anyone tuning CI test runs can follow tooling updates like this on daily.dev._ ## Similar posts on daily.dev - [Closed class hierarchies](https://daily.dev/posts/closed-class-hierarchies-xmmjyy63z) · .NET Escapades · 15 upvotes · 0 comments --- Tags: [#.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-7-what-s-new-before-the-november-release-qq7fnicrv) ```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 7: what's new before the November release","url":"https://daily.dev/posts/net-11-preview-7-what-s-new-before-the-november-release-qq7fnicrv","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/net-11-preview-7-what-s-new-before-the-november-release-qq7fnicrv"},"datePublished":"2026-08-12T15:28:53.994Z","dateModified":"2026-08-19T15:26:04.731Z","description":"Microsoft released .NET 11 Preview 7, a substantial update ahead of the November general availability. Highlights include tiered compilation for async methods...","image":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/fa1f970ba804856f51a19ac1c4d65119?_a=AQAEuop","thumbnailUrl":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/fa1f970ba804856f51a19ac1c4d65119?_a=AQAEuop","isAccessibleForFree":true,"articleSection":"Collections","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"Collections","logo":"https://media.daily.dev/image/upload/s--fk_6ycEi--/f_auto,q_auto/v1780996001/logos/collections?_a=BAMAMiWQ0","url":"https://daily.dev/sources/collections"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/net-11-preview-7-what-s-new-before-the-november-release-qq7fnicrv","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":13},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":".net,c#,aspnet","timeRequired":"PT2M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"Collections","item":"https://daily.dev/sources/collections"},{"@type":"ListItem","position":3,"name":".NET 11 Preview 7: what's new before the November release"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/net-11-preview-7-what-s-new-before-the-november-release-qq7fnicrv#faq","mainEntity":[{"@type":"Question","name":"What new async performance feature is in .NET 11 Preview 7?","acceptedAnswer":{"@type":"Answer","text":"NET 11 Preview 7 adds tiered compilation for async methods along with runtime-async tiering and tail-await optimizations. Async code should compile and run more efficiently without any changes needed in existing projects. This is one of several runtime improvements alongside continued work on running CoreCLR inside WebAssembly using a portable interpreter and R2R model. Track .NET 11's async runtime changes on daily.dev before rolling out the upgrade."}},{"@type":"Question","name":"Is NativeAOT enabled by default in .NET 11?","acceptedAnswer":{"@type":"Answer","text":"Yes, NativeAOT is now enabled by default for the dotnet CLI in .NET 11 Preview 7, and the MSBuild server is also on by default, which should speed up build times for many projects. This preview shipped ahead of the planned November general availability, following Preview 6 on July 14. Developers planning .NET 11 upgrades follow build tooling changes like this on daily.dev."}},{"@type":"Question","name":"What new options were added to dotnet test in .NET 11?","acceptedAnswer":{"@type":"Answer","text":"dotnet test in .NET 11 Preview 7 gained a run-level timeout option and a maximum-failed-tests flag, letting developers stop a test run early instead of waiting for it to finish entirely. These join a broader set of runtime, C#, ASP.NET Core, MAUI, EF Core, and Windows Forms updates in this preview. Anyone tuning CI test runs can follow tooling updates like this on daily.dev."}}]} ```