# C# 15

Preview version 15 of the C# programming language, supported by .NET 11 preview releases.

This is one page of public article previews, not the complete archive. Follow Next page to continue. Summaries are not the original full articles.

## Microsoft Releases .NET 11 RC1 with Go-Live Support, C# 15 and F# 11 as Default Language Versions

DevFeed: [Microsoft Releases .NET 11 RC1 with Go-Live Support, C# 15 and F# 11 as Default Language Versions](<https://devfeed.tech/articles/microsoft-releases-net-11-rc1-with-go-live-support-c-15-and-f-11-as-default-language-versions-26600.md>)

Original publisher: [Read original article](<https://www.infoq.com/news/2026/09/dotnet-11-rc-1-release/>)

Author: Almir Vuk

Published: 2026-09-15T07:11:00Z

Content type: news

Language: en

Sources: [InfoQ](<https://devfeed.tech/sources/infoq.md>)

Topics: [.NET 11](<https://devfeed.tech/topics/net-11.md>), [C# 15](<https://devfeed.tech/topics/c-sharp-15.md>), [Microsoft](<https://devfeed.tech/topics/microsoft.md>), [releases](<https://devfeed.tech/topics/releases.md>), [ASP.NET Core](<https://devfeed.tech/topics/asp-net-core.md>), [F#](<https://devfeed.tech/topics/fsharp.md>), [SignalR](<https://devfeed.tech/topics/signalr.md>), [SDKs](<https://devfeed.tech/topics/sdks.md>), [.NET MAUI](<https://devfeed.tech/topics/net-maui.md>), [native aot](<https://devfeed.tech/topics/native-aot.md>)

Tags: [android](<https://devfeed.tech/tags/android.md>), [api](<https://devfeed.tech/tags/api.md>), [asp-net-core](<https://devfeed.tech/tags/asp-net-core.md>), [c-sharp-15](<https://devfeed.tech/tags/c-sharp-15.md>), [development](<https://devfeed.tech/tags/development.md>), [dotnet-11-rc-1-release](<https://devfeed.tech/tags/dotnet-11-rc-1-release.md>), [f-sharp](<https://devfeed.tech/tags/f-sharp.md>), [ios](<https://devfeed.tech/tags/ios.md>), [macos](<https://devfeed.tech/tags/macos.md>), [microsoft](<https://devfeed.tech/tags/microsoft.md>), [native-aot](<https://devfeed.tech/tags/native-aot.md>), [net](<https://devfeed.tech/tags/net.md>), [net-10](<https://devfeed.tech/tags/net-10.md>), [net-11](<https://devfeed.tech/tags/net-11.md>), [net-9](<https://devfeed.tech/tags/net-9.md>), [net-core](<https://devfeed.tech/tags/net-core.md>), [net-maui](<https://devfeed.tech/tags/net-maui.md>), [news](<https://devfeed.tech/tags/news.md>), [releases](<https://devfeed.tech/tags/releases.md>), [sdk](<https://devfeed.tech/tags/sdk.md>), [signalr](<https://devfeed.tech/tags/signalr.md>)

### AI overview

Microsoft released .NET 11 Release Candidate 1 with go-live support for production use. It makes C# 15 and F# 11 the default language versions and stabilizes features from the preview cycle. The release also extends testing across mobile and desktop targets, updates SignalR authentication refresh APIs, and adds SDK, ASP.NET Core, Blazor, and Native AOT-related improvements.

### Source excerpt

Last week, Microsoft has released .NET 11 Release Candidate 1, the first release candidate of the cycle, shipping with a go-live support license for production use. The release makes C# 15 and F# 11 the default language versions, extends dotnet test to mobile and desktop targets, finalizes the SignalR authentication refresh APIs, and improves Android build times in .NET MAUI. By Almir Vuk

## Use C# unions and closed hierarchies in ASP.NET Core

DevFeed: [Use C# unions and closed hierarchies in ASP.NET Core](<https://devfeed.tech/articles/use-c-unions-and-closed-hierarchies-in-asp-net-core-2954.md>)

Original publisher: [Read original article](<https://devblogs.microsoft.com/dotnet/unions-and-closed-hierarchies-in-aspnetcore/>)

Author: Dmitrii Korolev

Published: 2026-09-10T17:00:00Z

Content type: tutorial

Language: en

Sources: [.NET Blog](<https://devfeed.tech/sources/net-blog.md>)

Topics: [C# 15](<https://devfeed.tech/topics/c-sharp-15.md>), [ASP.NET Core](<https://devfeed.tech/topics/asp-net-core.md>), [.NET](<https://devfeed.tech/topics/net.md>), [Polymorphism](<https://devfeed.tech/topics/polymorphism.md>)

Tags: [asp-net-core](<https://devfeed.tech/tags/asp-net-core.md>), [blazor](<https://devfeed.tech/tags/blazor.md>), [c-sharp](<https://devfeed.tech/tags/c-sharp.md>), [c-sharp-15](<https://devfeed.tech/tags/c-sharp-15.md>), [closed-hierarchies](<https://devfeed.tech/tags/closed-hierarchies.md>), [json](<https://devfeed.tech/tags/json.md>), [minimal-api](<https://devfeed.tech/tags/minimal-api.md>), [mvc](<https://devfeed.tech/tags/mvc.md>), [net](<https://devfeed.tech/tags/net.md>), [net-11](<https://devfeed.tech/tags/net-11.md>), [openapi](<https://devfeed.tech/tags/openapi.md>), [polymorphism](<https://devfeed.tech/tags/polymorphism.md>), [signalr](<https://devfeed.tech/tags/signalr.md>), [system-text-json](<https://devfeed.tech/tags/system-text-json.md>), [union-types](<https://devfeed.tech/tags/union-types.md>)

### AI overview

Explains how C# unions and closed hierarchies model API values with a fixed set of possible types in ASP.NET Core. It contrasts unions with open inheritance-based polymorphism and describes System.Text.Json support.

### Source excerpt

Learn how C# unions and closed hierarchies work with System.Text.Json across ASP.NET Core Minimal APIs, MVC, SignalR, Blazor, and OpenAPI. The post Use C# unions and closed hierarchies in ASP.NET Core appeared first on .NET Blog.

## .NET Conf 2026 - Save the Date

DevFeed: [.NET Conf 2026 - Save the Date](<https://devfeed.tech/articles/net-conf-2026-save-the-date-2948.md>)

Original publisher: [Read original article](<https://devblogs.microsoft.com/dotnet/dotnet-conf-2026/>)

Author: Jon Galloway

Published: 2026-08-25T16:28:27Z

Content type: news

Language: en

Sources: [.NET Blog](<https://devfeed.tech/sources/net-blog.md>)

Topics: [.NET Conf](<https://devfeed.tech/topics/net-conf.md>), [.NET](<https://devfeed.tech/topics/net.md>), [C# 15](<https://devfeed.tech/topics/c-sharp-15.md>), [ASP.NET Core](<https://devfeed.tech/topics/asp-net-core.md>), [Blazor](<https://devfeed.tech/topics/blazor.md>), [WebAssembly](<https://devfeed.tech/topics/web-assembly.md>), [Aspire](<https://devfeed.tech/topics/aspire.md>), [OpenAPI Specification](<https://devfeed.tech/topics/openapi.md>), [Model Context Protocol](<https://devfeed.tech/topics/model-context-protocol.md>)

Tags: [asp-net-core](<https://devfeed.tech/tags/asp-net-core.md>), [blazor](<https://devfeed.tech/tags/blazor.md>), [c-sharp-15](<https://devfeed.tech/tags/c-sharp-15.md>), [community](<https://devfeed.tech/tags/community.md>), [conference](<https://devfeed.tech/tags/conference.md>), [event](<https://devfeed.tech/tags/event.md>), [mcp](<https://devfeed.tech/tags/mcp.md>), [net](<https://devfeed.tech/tags/net.md>), [net-11](<https://devfeed.tech/tags/net-11.md>), [net-conf](<https://devfeed.tech/tags/net-conf.md>), [speakers](<https://devfeed.tech/tags/speakers.md>), [union-types](<https://devfeed.tech/tags/union-types.md>), [virtual-event](<https://devfeed.tech/tags/virtual-event.md>), [webassembly](<https://devfeed.tech/tags/webassembly.md>)

### AI overview

Microsoft announces .NET Conf 2026, a free online event running November 10-12, featuring community sessions and the launch of .NET 11. The article previews updates across .NET, including C# 15 union types, .NET MAUI, ASP.NET Core, Blazor, OpenAPI, Aspire, and the official MCP C# SDK.

### Source excerpt

.NET Conf returns November 10-12, 2026, with three days of sessions, community, and the launch of .NET 11. The post .NET Conf 2026 - Save the Date appeared first on .NET Blog.

## Explore new features available in C# 15 preview

DevFeed: [Explore new features available in C# 15 preview](<https://devfeed.tech/articles/explore-new-features-available-in-c-15-preview-2949.md>)

Original publisher: [Read original article](<https://devblogs.microsoft.com/dotnet/explore-csharp-15/>)

Author: Bill Wagner

Published: 2026-08-24T17:00:00Z

Content type: article

Language: en

Sources: [.NET Blog](<https://devfeed.tech/sources/net-blog.md>)

Topics: [C# 15](<https://devfeed.tech/topics/c-sharp-15.md>), [.NET](<https://devfeed.tech/topics/net.md>), [union types](<https://devfeed.tech/topics/union-types.md>), [.NET 11 Preview 7](<https://devfeed.tech/topics/net-11-preview-7.md>)

Tags: [blog](<https://devfeed.tech/tags/blog.md>), [c-sharp](<https://devfeed.tech/tags/c-sharp.md>), [c-sharp-15](<https://devfeed.tech/tags/c-sharp-15.md>), [closed-hierarchies](<https://devfeed.tech/tags/closed-hierarchies.md>), [dotnet](<https://devfeed.tech/tags/dotnet.md>), [features](<https://devfeed.tech/tags/features.md>), [net](<https://devfeed.tech/tags/net.md>), [net-11](<https://devfeed.tech/tags/net-11.md>), [net-11-preview-7](<https://devfeed.tech/tags/net-11-preview-7.md>), [union-types](<https://devfeed.tech/tags/union-types.md>)

### AI overview

An overview of the new features in C# 15, which ships with .NET 11. The article covers union types, closed hierarchies, the preview memory-safety redesign, and several smaller language changes.

### Source excerpt

C# 15 ships with .NET 11. It adds union types, closed hierarchies, a preview of the updated unsafe model, and a few smaller changes that remove everyday ceremony. The post Explore new features available in C# 15 preview appeared first on .NET Blog.