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If you're migrating an app to ASP.NET Core 9, the breaking changes listed here might affect you.
This article categorizes each breaking change as binary incompatible or source incompatible, or as a behavioral change:
Binary incompatible - When run against the new runtime or component, existing binaries may encounter a breaking change in behavior, such as failure to load or execute, and if so, require recompilation.
Source incompatible - When recompiled using the new SDK or component or to target the new runtime, existing source code may require source changes to compile successfully.
Behavioral change - Existing code and binaries may behave differently at runtime. If the new behavior is undesirable, existing code would need to be updated and recompiled.
| 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 |
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ASP.NET Core