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


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?


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


Below the code of the application:


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.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);    

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
            if (env.IsDevelopment())

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


            app.UseEndpoints(endpoints =>

            app.UseSwaggerUI(c =>
                c.SwaggerEndpoint("/swagger/v1/swagger.json", "GeoAPIs Ver 1.0.0");
                c.RoutePrefix = "docs";

Here is the launchsettings.json:

  "$schema": "",
  "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...

asked on Stack Overflow Oct 5, 2019 by Giox • edited Oct 5, 2019 by Giox

7 Answers


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

enter image description here

3.) Restart your solution again

answered on Stack Overflow Nov 4, 2019 by Legends • edited Sep 14, 2020 by Legends

Thanks to @Lex Li he has given me the solution.

The issue was in the applicationhost.config, the metabase file containing all the settings for the IISExpress launch by Visual Studio to run your web application.

For Visual Studio 2019, this file is located in


For other version check this post: Where is the IIS Express configuration / metabase file found?

under the section I had the following:

  <site name="WebSite1" id="1" serverAutoStart="true">
    <application path="/">
      <virtualDirectory path="/" physicalPath="%IIS_SITES_HOME%\WebSite1" />
      <binding protocol="http" bindingInformation=":8080:localhost" />

  <site name="MyProjectName" id="2">
    <application path="/" applicationPool="MyProjectName AppPool">
      <virtualDirectory path="/" physicalPath="E:\Projects\MyProjectName" />

   <application path="/docs" applicationPool="docs AppPool">
      <virtualDirectory path="/" physicalPath="E:\Projects\MyProjectName" />

      <binding protocol="http" bindingInformation="*:59386:localhost" />
      <binding protocol="https" bindingInformation="*:44345:localhost" />
    <!-- To enable logging, please change the below attribute "enabled" to "true" -->
    <logFile logFormat="W3C" directory="%AppData%\Microsoft\IISExpressLogs" enabled="false" />
    <traceFailedRequestsLogging directory="%AppData%\Microsoft" enabled="false" maxLogFileSizeKB="1024" />
  <applicationDefaults applicationPool="Clr4IntegratedAppPool" />
  <virtualDirectoryDefaults allowSubDirConfig="true" />

Where there are some strange setting defined by

<application path="/docs" applicationPool="docs AppPool">
   <virtualDirectory path="/" physicalPath="E:\Projects\MyProjectName" />

that has been certainly added when I've tried to set as start folder the /docs path.

Commenting out this setting and another one at the end of the file related to this path has solved the issue.

answered on Stack Overflow Oct 5, 2019 by Giox

I got the same error when I did the following:

  1. Published two separate core websites
  2. In IIS, created two websites under "Default Web Site", each having physical path set to each of the publish folders in (1) respectively.
  3. Now whichever of the sites I open first works, and the second gives that error.


Since both my sites are under "Default Web Site" they are both using DefaultAppPool, which is the cause of this error. The same error occurs when the sites are not under "Default Web Site" but use the same app pool.


As mentioned in the docs,

To fix this error, run apps in separate IIS application pools.

for me this problem was resolved when I started using separate app pools for each site.

answered on Stack Overflow Oct 25, 2019 by Sнаđошƒаӽ • edited Jan 14, 2020 by Sнаđошƒаӽ

I fixed the issue by deleting V2 in web.config file generated after publishing the solution.

    <add name="aspNetCore" path="*" verb="*" 
        modules="AspNetCoreModule" resourceType="Unspecified" />

instead of

    <add name="aspNetCore" path="*" verb="*"
        modules="AspNetCoreModuleV2" resourceType="Unspecified" />
answered on Stack Overflow Jun 1, 2020 by Michel El Hajj • edited Nov 10, 2020 by SimplyInk

In .csproj file, set:


Allow host the same pool

answered on Stack Overflow Aug 20, 2020 by Diego Venâncio

I had the same problem.

Add this line in .csproj file in Tag: <AspNetCoreHostingModel>OutOfProcess</AspNetCoreHostingModel>

Although it is the 500.30 error it also fixed the 500.35 problem.

HTTP Error 500.30 - ANCM In-Process Start Failure

I hope help you.

Best regards.

answered on Stack Overflow Aug 21, 2020 by Federico

The Most Easy And Reliable think which worked for me is , just simply put a simple index.html in main application , and treat every application in your solution as subapplications.

answered on Stack Overflow Dec 15, 2020 by Hamza javed

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