Breaking changes in ASP.NET Core 9

If you're migrating an app to ASP.NET Core 9, the breaking changes listed here might affect you.

[!INCLUDE binary-source-behavioral]

Title	Type of change
DefaultKeyResolution.ShouldGenerateNewKey altered meaning	Behavioral change
Dev cert export no longer creates folder	Behavioral change
Forwarded Headers Middleware ignores X-Forwarded-* headers from unknown proxies	Behavioral change
HostBuilder enables ValidateOnBuild/ValidateScopes in development environment	Behavioral change
Legacy Mono and Emscripten APIs not exported to global namespace	Source incompatible
Middleware types with multiple constructors	Behavioral change