How to fix "No webpage was found for the web address: http://localhost:5000/swagger/v1/swagger.json" error?

Question

I am working on the "Improve the developer experience of an API with Swagger documentation" module.

When I run the code and navigate to [http://localhost:5000/api/priceframe/6/17], the browser looks as expected. However, after adding the Swashbuckle.AspNetCore package, making the specified code changes and trying to navigate to [http://localhost:5000/swagger/v1/swagger.json], I get the following error on my browser:

This localhost page can’t be found

No webpage was found for the web address: http://localhost:5000/swagger/v1/swagger.json

HTTP ERROR 404

Why isn't this working?

Here is what the code in Startup.cs file looks like:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.HttpsPolicy;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using Microsoft.OpenApi.Models;

namespace PrintFramerAPI
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllers();

            services.AddSwaggerGen(c =>
            {
                c.SwaggerDoc("v1", new OpenApiInfo { Title = "My API", Version = "v1" });
            });
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseSwagger();
                app.UseSwaggerUI(c =>
                {
                    c.SwaggerEndpoint("/swagger/v1/swagger.json", "My API V1");
                    c.RoutePrefix = string.Empty;
                });

                app.UseDeveloperExceptionPage();
            }

            app.UseHttpsRedirection();

            app.UseRouting();

            app.UseAuthorization();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();
            });
        }
    }
}

This question is related to the following Learning Module

Answer 1

Hi Mara McConnell, 

Thank you for reaching out to Microsoft Q & A forum.  

This issue is likely caused by the absence of a launchSettings.json file. This file is essential for defining the application's URL and environment settings during local development. Without it, the application might not run at the expected URL or be properly configured to serve Swagger. 

To resolve this issue, create the missing launchSettings.json file. This file configures the application's URL, specifies whether HTTPS should be used, and sets environment variables. 

1.Create the launchSettings.json File 

In your project directory, navigate to the Properties folder. 

If the Properties folder doesn’t exist, create it. 

Inside the folder, create a file named launchSettings.json. 

2.Add Configuration to the File 

Paste the following content into launchSettings.json: 

{
    "profiles": {
      "PrintFramerAPI": {
        "commandName": "Project",
        "dotnetRunMessages": true,
        "launchBrowser": true,
        "applicationUrl": "
        "environmentVariables": {
          "ASPNETCORE_ENVIRONMENT": "Development"
        }
      }
    }
  }

"applicationUrl": "http://localhost:5000",

3.Run the Application 

Save your changes (Ctrl+S),

Restart the application using the following command: 

dotnet run

Please feel free to contact us if you have any additional questions.    

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