I don't understand why my Minimal API doesn't bring up swagger

Hi @Jack Dang (WICLOUD CORPORATION) I've tried some of what you suggested. I'll go over what I've tried and what I haven't tried.

Concerning app.Environment.IsDevelopment() returns True.

I've checked the launchSettings.json file to make sure that ASPNETCORE_ENVIRONMENT is set to "Development". It wasn't, but I've corrected that so now it does.

Concerning duplicate Swagger configurations, I believe this is where my problems arise. I found that I have what looks to me to be 3 Swagger configurations. At least one of them is due to GitHub Copilot, when I was trying to use it to resolve this issue, but it seems to have added a Swager configuration, rather than having used what was already there. And the third, well that came from a conversation I had with Microsoft technical support, when I was trying to access Azure Key Vault, they had me put in another Swager configuration, rather than use what was already there. Anyway, I now have 2 active ones, I think, the first one uses SwaggerDoc which I am not familiar with and am not sure what it does, but I'll give it here:

builder.Services.AddSwaggerGen(c =>
{
    c.SwaggerDoc("v1", new OpenApiInfo
    {
        Title = "FPTimetrackCore.DataActionsAPI",
        Version = "v1"
    });
});

The second one is this:

if (app.Environment.IsDevelopment())

{

app.UseSwagger();

app.UseSwaggerUI(c =>

{

    c.SwaggerEndpoint("/swagger/v1/swagger.json", "FPTimetrackCore.DataActionsAPI v1");

});

}

And lastly, when I tried to navigating directly to the Minimal API URL using https://localhost:5001/swagger I got this:

there are multiple parts to openapi and swagger. the default webapi project just include openapi, which you seem to have removed.

builder.Services.AddOpenApi();

the openapi service builds the the explorer mapping at compile so reflection is not required. it supplies an endpoint (openapi/v1.json) that returns a json file that defines the api.

to add the swagger UI, you pick a 3rd party package, either nswag or swashbuckle. you then configure them to use the open api. while these packages also support their own mapping software, they don't support minapi as there is not enough.

its not clear which 3rd party package you picked, but looks like swashbuckle. you only need the ui package, as webapi has the endpoint generation:

// add .net core openapi support services
builder.Services.AddOpenApi();   

var app = builder.Build();

if (app.Environment.IsDevelopment())
{
    // .net core openapi middleware
    app.MapOpenApi();

    // swashbuckle UI (nuget Swashbuckle.AspNetCore.SwaggerUI)
    app.UseSwaggerUI(options => // UseSwaggerUI is called only in Development.
    {
        options.SwaggerEndpoint("openapi/v1.json", "v1");
        options.RoutePrefix = string.Empty; // make default route
    });
}

OK, I've got another question for you all. I decided to create a new Minimal API project based solely on Microsoft's Minimal API project template for .NET 9. I included Swagger support, but other than that I didn't add anything to it. Then I built it and started to debug it. First, when I started to debug it, no browser instance opened. So, I opened a browser (I tried both MS Edge and Chrome) and gave it the URL: https://localhost:7145/swagger. That failed immediately with a HTTP error of 404.

Why did that happen if it was supposed to find the Swagger UI??

Note that when I tried the URL of https://localhost:7145/weatherforecast to bring back the result of calling the WeatherForecast endpoint, that it worked fine.

Now, I'm going to be paranoid and ask a question which I hope isn't real. Could it be that any use of Swagger is blocked?

then you did not add the support correctly. try (assumes code is vs code, but you can use any editor, even notepad):

open a console:

mkdir testapi
cd testapi
dotnet new webapi
dotnet add package Swashbuckle.AspNetCore.SwaggerUI
dotnet restore
code program.cs

in program.cs after app.MapOpenApi(); (line 15) add:

    app.UseSwaggerUI(options =>
    {
        options.SwaggerEndpoint("openapi/v1.json", "v1");
        options.RoutePrefix = string.Empty;
    });

after editing and saving the added 5 lines of code exit and continue in the console:

dotnet build
dotnet run

if you open the url in the browser. you should see the swagger UI.

full code source:

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
// Learn more about configuring OpenAPI at https://aka.ms/aspnet/openapi
builder.Services.AddOpenApi();

var app = builder.Build();

// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{
    app.MapOpenApi();
    app.UseSwaggerUI(options => 
    {
        options.SwaggerEndpoint("openapi/v1.json", "v1");
        options.RoutePrefix = string.Empty;
    });
}

app.UseHttpsRedirection();

var summaries = new[]
{
    "Freezing", "Bracing", "Chilly", "Cool", "Mild", "Warm", "Balmy", "Hot", "Sweltering", "Scorching"
};

app.MapGet("/weatherforecast", () =>
{
    var forecast =  Enumerable.Range(1, 5).Select(index =>
        new WeatherForecast
        (
            DateOnly.FromDateTime(DateTime.Now.AddDays(index)),
            Random.Shared.Next(-20, 55),
            summaries[Random.Shared.Next(summaries.Length)]
        ))
        .ToArray();
    return forecast;
})
.WithName("GetWeatherForecast");

app.Run();

record WeatherForecast(DateOnly Date, int TemperatureC, string? Summary)
{
    public int TemperatureF => 32 + (int)(TemperatureC / 0.5556);
}