Fix Swagger UI configuration to use NSwag instead of Swashbuckle

[Astroa7m]

The tutorial code used Swashbuckle's UseSwaggerUI() method, but the project already has NSwag.AspNetCore installed.

This causes a compilation error: "'WebApplication' does not contain a definition for 'UseSwaggerUI'". The code should use NSwag's UseSwaggerUi() instead.

[hooseinsaid]

Great fix. The changes correctly replace the Swashbuckle-specific configuration with NSwag equivalents, resolving the compilation issue and aligning with the project’s existing setup.

The implementation is clean and consistent, and the Swagger UI is now working as expected.

[wadepickett]

@copilot
The Swashbuckle.AspNetCore package reference should be removed from the 9.x .csproj. Remove it.
Why:

• The 9.x article never tells users to install Swashbuckle. The only Swagger-related package the tutorial instructs users to add is NSwag.AspNetCore (line 438 of the article).

• The 9.x Program.cs doesn't use any Swashbuckle APIs. It uses AddOpenApi() / MapOpenApi() (built-in .NET 9) for OpenAPI document generation, and UseSwaggerUi() (NSwag) for the Swagger UI. There is no AddSwaggerGen(), UseSwagger(), or Swashbuckle's UseSwaggerUI() anywhere in the 9.x code.

• It's a leftover from the 7.x/8.x templates and app samples, which did use Swashbuckle. It was never cleaned up when the 9.x sample was created with the new OpenAPI + NSwag approach.

[wadepickett]

@Astroa7m, thanks so much for pointing out this issue and correcting it. Greatly appreciated!
Reviewing....

[Copilot]

Pull request overview

Updates the ASP.NET Core 9.x first-mongo-app tutorial sample to use NSwag’s Swagger UI middleware (already referenced by the sample) instead of Swashbuckle’s UseSwaggerUI, resolving the reported compilation error and aligning with the repo’s modern OpenAPI pattern.

Changes:

• Replace UseSwaggerUI with NSwag UseSwaggerUi.
• Update UI configuration from SwaggerEndpoint(...) to DocumentPath = "/openapi/v1.json" to match MapOpenApi() output.

[wadepickett]

@Astroa7m , I can approve and merge after policy agreement addressed above. Thanks again for the fix!

[wadepickett]

Approved and will be merged when Contributor License Agreement(CLA) is signed off.

[Astroa7m]

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[wadepickett]

Great work, thanks!!! Will merge to live today.