I am trying to configure my .NET 9 Aspire App Web API with OpenAI to use Swagger. I tried the code at this link, but I get CORS error when I try to execute in Swagger UI:

.0

The example works if the API is standalone (not orchestrated in Aspire). What do I need to do to get this to work in Aspire?

NOTE: I tried with Scalar as well but it just failed the fetch; did not give me an error message.

I am trying to configure my .NET 9 Aspire App Web API with OpenAI to use Swagger. I tried the code at this link, but I get CORS error when I try to execute in Swagger UI:

https://learn.microsoft/en-us/aspnet/core/fundamentals/openapi/using-openapi-documents?view=aspnetcore-9.0

The example works if the API is standalone (not orchestrated in Aspire). What do I need to do to get this to work in Aspire?

NOTE: I tried with Scalar as well but it just failed the fetch; did not give me an error message.

• swagger-ui
• dotnet-aspire

• 1 The "servers" list under the OpenAPI "localhost:port/openapi/v1.json" have different ports than the Web API. Which causes CORS issues. Aspire seems to influence the OpenAPI, causing it to generate different ports than the ones stated in the launchSettings.json. Not sure how to solve it right now – HenrikP Commented Nov 21, 2024 at 17:59

2 Answers 2

A solution for Scalar is to empty the server list:

app.MapScalarApiReference(options =>
{
    options.Servers = [];
});

Credit to: https://github/dotnet/aspnetcore/issues/57332#issuecomment-2479286855

I am uncertain how to do this for Swagger with OpenAPI.

You need to enable CORS

builder.Services.AddCors(options =>
{
    options.AddPolicy("GetorPost",
        builder =>
        builder.AllowAnyOrigin().WithMethods("GET", "POST")
        .AllowAnyHeader());
});

//.....

if (app.Environment.IsDevelopment())
{
    app.UseCors("GetorPost");
}