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Tag: openapi

15 posts · Page 1 of 2

2026-08-19 errors swashbuckle openapi

Fix: cannot target OpenAPI 3.0 after upgrading Swashbuckle.AspNetCore to v9

Swashbuckle 8 and later emit openapi 3.0.4, not 3.0.1, and there is no OpenApiSpecVersion for a patch version. Why it changed, and four ways to pin the string your tooling expects.

2026-08-19 errors openapi swagger

Fix: Swagger UI shows Unable to render this definition after upgrading to .NET 11

ASP.NET Core 11 emits openapi 3.2.0 by default and Swagger UI below 10.1.5 rejects it. Upgrade Swashbuckle.AspNetCore.SwaggerUI, or pin OpenApiVersion back to OpenApi3_1.

2026-08-15 comparison csharp dotnet

Scalar vs Swagger UI for OpenAPI documentation in ASP.NET Core 11

Scalar ships 1.02 MiB of gzipped JavaScript and a far better request builder. Swagger UI ships 514 KiB and renders OpenAPI 3.2, which is what .NET 11 now emits by default. Measured payloads, the 3.2 gap, endpoint routing on both sides, and the auth details that decide it.

2026-08-12 errors aspnetcore dotnet

Fix: The 'interceptors' feature is not enabled in this namespace

CS9137 comes from the Microsoft.AspNetCore.OpenApi source generator. Add InterceptorsNamespaces to every project that calls AddOpenApi, not just the one holding the PackageReference.

2026-08-11 errors aspnetcore dotnet

Fix: The type or namespace name 'OpenApiReference' could not be found

OpenApiReference was deleted in Microsoft.OpenApi 2.0. Changing the using to Microsoft.OpenApi is not enough: replace each usage with a typed reference such as OpenApiSchemaReference.

2026-08-09 csharp dotnet dotnet-11

How to serve OpenAPI documentation with Scalar instead of Swagger UI in ASP.NET Core 11

Replace UseSwaggerUI with MapScalarApiReference in ASP.NET Core 11: routing, multiple documents, pre-filled auth, production gating, offline assets, and the Scalar-only OpenAPI extensions that mark endpoints stable or hidden.

2026-07-24 migration swashbuckle openapi

Migrate Swashbuckle IOperationFilter and ISchemaFilter to OpenAPI transformers in .NET 11

A filter-by-filter porting reference for moving Swashbuckle IOperationFilter and ISchemaFilter code to the built-in operation and schema transformers in .NET 11, with the context-object field mapping and the Microsoft.OpenApi v2 changes that bite.

2026-07-14 csharp dotnet dotnet-11

How to return a typed Results<T1, T2> union from a minimal API endpoint in ASP.NET Core 11

Declare the handler's return type as Results<Ok<T>, NotFound> and return TypedResults.Ok / TypedResults.NotFound: the union gives compile-time checking that the handler only returns what it declares, and it self-describes to OpenAPI so you never write .Produces by hand. Covers async handlers, the six-type limit, and testing in ASP.NET Core 11.

2026-07-12 csharp dotnet dotnet-11

How to customize the OpenAPI document with AddOperationTransformer and AddSchemaTransformer in ASP.NET Core 11

A deep dive into the built-in OpenAPI transformer pipeline in .NET 11: operation vs schema transformers, the context objects, execution order, DI-activated transformers, and recipes for headers, responses, examples, and per-property tweaks.

2026-06-16 migration swashbuckle openapi

Migrate from Swashbuckle to the built-in OpenAPI generator in .NET 11

A step-by-step migration from Swashbuckle.AspNetCore to Microsoft.AspNetCore.OpenApi in .NET 11: swapping AddSwaggerGen for AddOpenApi, converting operation, schema, and document filters to transformers, keeping a UI, and the Microsoft.OpenApi v2 breaking changes that bite.