OpenAPI issue

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OpenAPI issue

Peter_1985 3,151

Hi,

How to resolve it below? I ever changed OpenAPI version to 3.3.1 but there was the other issue.

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Answer 1

Jack Dang (WICLOUD CORPORATION) 14,955 Microsoft External Staff Moderator

Hi @Peter_1985 ,

Thanks for reaching out.

The issue you’re seeing is caused by a version mismatch between your packages. Specifically, Swashbuckle.AspNetCore 10.1.1 requires Microsoft.OpenApi >= 2.4.1, but your project references Microsoft.OpenApi 1.6.*. This triggers the NU1605 warning, which in your case is treated as an error.

To resolve this, you can update your project to make the package versions compatible. Since you’re on .NET 8, here’s a simple approach:

Update your project file to reference compatible versions:

<TargetFramework>net8.0</TargetFramework>
<PackageReference Include="Microsoft.AspNetCore.OpenApi" Version="8.0.*" />
<PackageReference Include="Microsoft.OpenApi" Version="2.4.1" />
<PackageReference Include="Swashbuckle.AspNetCore" Version="10.1.1" />

Clean and rebuild the project:

dotnet clean
# optionally delete bin and obj folders
dotnet restore
dotnet build

Make sure your code files include the correct namespace:

using Microsoft.OpenApi.Models;

Hope this helps! If my answer was helpful - kindly follow the instructions here so others with the same problem can benefit as well.

Peter_1985 3,151 Reputation points

2026-02-09T08:41:46.63+00:00

Yes, I built it but there was still the issue below
Jack Dang (WICLOUD CORPORATION) 14,955 Reputation points Microsoft External Staff Moderator

2026-02-09T08:53:43.25+00:00
Hi @Peter_1985 ,

Thanks for your feedback.

This error happens because Microsoft.OpenApi.Models is not being found by the compiler.

Please check two things:

Make sure Microsoft.OpenApi is version 2.4.1 or newer, since Swashbuckle.AspNetCore 10.1.1 requires it:

<PackageReference Include="Microsoft.OpenApi" Version="2.4.1" />

Remove this line from Program.cs (it’s not needed for minimal APIs and can cause confusion):

using Microsoft.AspNetCore.OpenApi;

After that, run:

dotnet clean dotnet restore dotnet build
Peter_1985 3,151 Reputation points

2026-02-09T09:03:34.68+00:00

Do we need any other certificate due to the following?
Jack Dang (WICLOUD CORPORATION) 14,955 Reputation points Microsoft External Staff Moderator

2026-02-09T09:39:01.0966667+00:00

Hi @Peter_1985 ,

Regarding your concern, no additional certificate is required. This prompt is normal when running the app locally over HTTPS.

ASP.NET uses a development HTTPS certificate for localhost. Since it’s self-signed, Windows can’t verify it and shows this warning. If this is your own local app, it’s safe to click Yes.
Peter_1985 3,151 Reputation points

2026-02-09T09:48:19.55+00:00

How to ensure that the link like

https://localhost:7060/swagger/index.html

is ready to be triggered by the client App (or to receive any command from the client side)?
Jack Dang (WICLOUD CORPORATION) 14,955 Reputation points Microsoft External Staff Moderator

2026-02-09T09:59:04.7833333+00:00

Hi @Peter_1985 ,

Thanks for the follow-up.

Based on the changes discussed earlier, the original OpenAPI/Swagger issue (package conflicts and build errors) should now be resolved. If your project builds successfully and Swagger loads in the browser, that confirms the initial problem is fixed.

The question about making

https://localhost:7060/swagger/index.html

accessible to a client app is a separate topic related to app hosting and runtime configuration, rather than OpenAPI itself. I’d suggest creating a new question for this, since each thread is best focused on a single issue.

If the OpenAPI issue is resolved on your side, kindly follow the instructions here so others with the same problem can benefit as well.
Peter_1985 3,151 Reputation points

2026-02-09T10:05:12.66+00:00

Thanks a lot. I raised

https://learn.microsoft.com/en-us/answers/questions/5767684/ensure-that-the-server-side-is-ready

already.

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