Fix: CS8509 or CS0161 on a switch that is exhaustive over a C# 15 union type
Switch on the union value, not .Value, and use a switch expression or add case null to a switch statement. Statements need null coverage that expressions only warn about.
csharp-15
7 posts
C# Unions in ASP.NET Core 11: Bodies, SignalR, and OpenAPI Work, Query Strings Do Not
The ASP.NET Core team mapped out where C# 15 union types flow through .NET 11: minimal API and MVC bodies, SignalR's JsonHubProtocol, Blazor, and OpenAPI anyOf schemas. Route, query, header, and form binding are not supported yet.
C# 15 Gets Labeled break and continue in .NET 11 Preview 7
Labeled break and continue landed in the C# section of .NET 11 Preview 7. You can now put a label on a loop and jump straight to it, which retires the bool flag and goto workarounds for nested loops.
C# 15 Extension Indexers Round Out Extension Members in .NET 11 Preview 6
Extension indexers landed in .NET 11 Preview 6, letting you add this[...] access to types you do not own. They complete the extension members story that started with methods and properties in C# 14.
C# 15 Closed Class Hierarchies: The closed Keyword in .NET 11 Preview 5
C# 15 adds the closed modifier in .NET 11 Preview 5, giving class hierarchies compile-time exhaustiveness in switch expressions. Here is how it works and the one gotcha.
C# 15 Collection Expression Arguments: Pass Constructors Inline with with(...)
C# 15 adds the with(...) element to collection expressions, letting you pass capacity, comparers, and other constructor arguments directly in the initializer.
C# 15 Union Types Are Here: Type Unions Ship in .NET 11 Preview 2
C# 15 introduces the union keyword for type unions with exhaustive pattern matching and implicit conversions. Available now in .NET 11 Preview 2.