Swashbuckle vs. NSwag in ASP.NET Core: .NET 10, built-in OpenAPI baseline, benchmark fixes

[vladimir-pecanac-main]

Sample update for the article "Swashbuckle vs. NSwag in ASP.NET Core" (https://code-maze.com/aspnetcore-swashbuckle-vs-nswag/).

Changes, all inside dotnet-client-libraries/SwashbuckleVsNSwag:

• Every project moves from net7.0 to net10.0.
• New SwashbuckleVsNSwag.BuiltIn project: the built-in generator (AddOpenApi(), MapOpenApi() for JSON and MapOpenApi("/openapi/{documentName}.yaml") for YAML) with Swagger UI from Swashbuckle.AspNetCore.SwaggerUi pointed at /openapi/v1.json, reusing the Models and Repositories projects and the same three controllers.
• Swashbuckle project: Swashbuckle.AspNetCore 6.4.0 to 10.3.0. Microsoft.OpenApi 2.x moved OpenApiInfo, so using Microsoft.OpenApi.Models; becomes using Microsoft.OpenApi; (without it the build fails with CS0234).
• NSwag project: NSwag.AspNetCore 13.19.0 to 14.7.1. Adds UseSwaggerUi (the NSwag 14 name; UseSwaggerUi3 was removed) at /swagger; ReDoc moves to /redoc because both default to /swagger.
• Benchmark: the URLs are fixed first. GET asked for /customer/{id} while the controller takes customerId as a query parameter, and the host's trailing slash plus "/customer" produced //customer, which also returns 404 for POST. Then the missing await on NSwag_GetResponse is added, and POST calls EnsureSuccessStatusCode so a failing request can no longer be timed. Console.ReadKey removed so the runner exits on its own.
• Test projects: SwashbuckleVsNSwag.Swachbuckle.Tests renamed to SwashbuckleVsNSwag.Swashbuckle.Tests, the six *ConsollerTest files and classes renamed to *ControllerTest, and the Swashbuckle tests use their own namespace instead of the NSwag one.
• SwashbuckleVsNSwagTests did not compile (a field declaration with no name) and was not in the solution. It is repaired, joins the solution and now tests the BuiltIn project with WebApplicationFactory: JSON document 200, YAML document 200, Swagger UI 200.
• The bare SwashbuckleVsNSwag template project (WeatherForecast, no OpenAPI code, referenced by nothing, not in the solution) is removed.
• README added: what each project shows and how to run the benchmark (both apps must be running on their https profiles).

Package versions, re-queried on NuGet on 2026-10-10 (latest listed stable):

• Microsoft.AspNetCore.OpenApi 10.0.12
• Swashbuckle.AspNetCore 10.3.0
• Swashbuckle.AspNetCore.SwaggerUi 10.3.0
• NSwag.AspNetCore 14.7.1
• BenchmarkDotNet 0.15.8
• Microsoft.NET.Test.Sdk 18.10.1
• NUnit 5.0.0
• NUnit3TestAdapter 6.3.1
• NUnit.Analyzers 4.15.0
• coverlet.collector 10.1.0
• Microsoft.AspNetCore.Mvc.Testing 10.0.12
• Moq 4.18.4 (held at or below 4.18.4 by policy)

Local results on SDK 10.0.302 / runtime 10.0.10: dotnet build -c Release 0 errors, 2 warnings (pre-existing CS8618 in the Models project); dotnet test 15 passed, 0 failed (6 + 6 + 3); dotnet list package --vulnerable --include-transitive reports no vulnerable packages in any project.