c# - HTTP Error 500.35 - ANCM Multiple In-Process Applications in same Process ASP.NET Core 3

Question

From this morning without any changes to the code of the project, a very simple Web API, one controller and 3 methods, with Swagger, it doesn't start anymore and I get the error:

HTTP Error 500.35 - ANCM Multiple In-Process Applications in same Process

Event viewer report the most useless message:

IIS Express AspNetCore Module V2: Failed to start application '/LM/W3SVC/2/ROOT/docs', ErrorCode '0x80004005'.

Restarted the system several times.

I'm using Visual Studio 2019, the application successfully compile and a few minutes ago it was working fine. No new software has been installed, no packages added. Tried also clean and rebuild.

I've just modified the comment of a method. Obviously I've tried also to restore the previous comment but I get always the same message.

What can I do?

Is net core still too unstable to be used professionally?

UPDATE

The same code launched from the same version of Visual Studio but in another PC runs properly.

UPDATE 2

Below the code of the application:

startup.cs

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.FileProviders;
using Microsoft.Extensions.Hosting;
using Microsoft.OpenApi.Models;
using System;
using System.IO;
using System.Reflection;

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

        public IConfiguration Configuration { get; }

        public void ConfigureServices(IServiceCollection services)
        {

            services.AddControllers(); 
            services.AddSwaggerGen(c =>
            {
                c.SwaggerDoc("v1", new OpenApiInfo() { Title = "Geographic APIs", Version = "v1.0.0" });
                var xmlFile = $"{Assembly.GetExecutingAssembly().GetName().Name}.XML";
                var xmlPath = Path.Combine(AppContext.BaseDirectory, xmlFile);    
                c.IncludeXmlComments(xmlPath);
            });
        }

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.UseStaticFiles(new StaticFileOptions
            {
                FileProvider = new PhysicalFileProvider(
                 Path.Combine(Directory.GetCurrentDirectory(), "swagger-ui")),
                RequestPath = "/swagger-ui"
            });

            app.UseHttpsRedirection();
            app.UseRouting();
            app.UseAuthorization();

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

            app.UseSwagger();    
            app.UseSwaggerUI(c =>
            {
                c.SwaggerEndpoint("/swagger/v1/swagger.json", "GeoAPIs Ver 1.0.0");
                c.RoutePrefix = "docs";
                c.InjectStylesheet("/swagger-ui/custom.css");
            });
        }
    }
}

Here is the launchsettings.json:

{
  "$schema": "http://json.schemastore.org/launchsettings.json",
  "iisSettings": {
    "windowsAuthentication": false, 
    "anonymousAuthentication": true, 
    "iisExpress": {
      "applicationUrl": "http://localhost:51319",
      "sslPort": 44345
    }
  },
  "profiles": {
    "IIS Express": {
      "commandName": "IISExpress",
      "launchBrowser": true,
      "launchUrl": "docs",
      "environmentVariables": {
        "ASPNETCORE_ENVIRONMENT": "Development"
      }
    },
    "WFP_GeoAPIs": {
      "commandName": "Project",
      "launchBrowser": true,
      "launchUrl": "docs",
      "applicationUrl": "https://localhost:5001;http://localhost:5000",
      "environmentVariables": {
        "ASPNETCORE_ENVIRONMENT": "Development"
      }
    }
  }
}

but coping the project on another PC with the same Visual Studio version works fine, so it looks like the is a configuration bug in the .NET Core or VIsual Studio property...

Answer 1

It's currently a bug in VS2019 - (Nov 4 '2019)

1.) Close your solution

2.) Delete applicationhost.config in folder .vs or delete the whole .vs folder.

The .vs folder is a hidden folder and is next to your solution file usually.

3.) Restart your solution again