Swagger UI interface in ASP.NET Core 3.1

Step 1. Create an ASP.NET Core Web Application and select API template and DemoSwaggerUI as your project name

Step 2. Install Swashbuckle from Package Manager in your project

Install-Package Swashbuckle.AspNetCore -Version 5.0.0

Step 3. Insert the following statements to Startup.cs

using Microsoft.OpenApi.Models;
public void ConfigureServices(IServiceCollection services)
{
    services.AddControllers();
    // Register the Swagger generator, defining 1 or more Swagger documents
    services.AddSwaggerGen(c =>
    {
        c.SwaggerDoc("v1", new OpenApiInfo
        {
            Version = "v1",
            Title = "ToDo API",
            Description = "A simple example ASP.NET Core Web API",
            TermsOfService = new Uri("https://example.com/terms"),
            Contact = new OpenApiContact
            {
                Name = "Nicky Liu",
                Email = "nicky@zedotech.com",
                Url = new Uri("https://www.zedotech.com"),
            },
            License = new OpenApiLicense
            {
                Name = "Use under LICX",
                Url = new Uri("https://example.com/license"),
            }
        });
    });
}
public void Configure(IApplicationBuilder app)
{
    // Enable middleware to serve generated Swagger as a JSON endpoint.
    app.UseSwagger();
    // Enable middleware to serve swagger-ui (HTML, JS, CSS, etc.),
    // specifying the Swagger JSON endpoint.
    app.UseSwaggerUI(c =>
    {
        c.SwaggerEndpoint("/swagger/v1/swagger.json", "My API V1");
    });
    app.UseRouting();
    app.UseEndpoints(endpoints =>
    {
        endpoints.MapControllers();
    });
}

Then run the application, you will see this screen in localhost:xxxxx/index.html

Step 4. Display API comments in UI

First, you need to insert the following statements in DemoSwaggerUI.csproj

<PropertyGroup>
<TargetFramework>netcoreapp3.1</TargetFramework>
<GenerateDocumentationFile>true</GenerateDocumentationFile>
<NoWarn>$(NoWarn);1591</NoWarn>
</PropertyGroup>

Second, add a triple-slash comment to WeatherForecast/Get action

/// <summary>
/// Get weathers
/// </summary>
/// <returns></returns>

Then re-run the application, you will see your description like this

Step 5. Display more description details

Insert comment to <remarks> block

/// <summary>
/// Get weathers
/// </summary>
/// <remarks>
/// Description
///
///     GET /WeatherForecast
///     This will return a WeatherForecast object array
///
/// </remarks>
/// <returns></returns>

Then re-run the application, you will see your description like this

Reference:
https://docs.microsoft.com/en-us/aspnet/core/tutorials/getting-started-with-swashbuckle?view=aspnetcore-3.1&tabs=visual-studio

Download this complete code sample on GitHub