NullReferenceException After Upgrading Microsoft.CodeDom.Providers.DotNetCompilerPlatform from Version 3.6.0 to 3.11.0 or 4.1.0

[rubenc57]

After upgrading Microsoft.CodeDom.Providers.DotNetCompilerPlatform from version 3.6.0 to either 3.11.0 or 4.1.0, I encountered the following error message:

Microsoft.CodeDom.Providers.DotNetCompilerPlatform failed to uninstall. Restart Visual Studio to finish process.

Upon restarting Visual Studio and running my website, I received this error: System.NullReferenceException HResult=0x80004003 Message=Object reference not set to an instance of an object. Source=CMS StackTrace: at CMS.Startup.ConfigureAuth(IAppBuilder app) in D:\Mis Proyectos\VS22\websites\jw\CMS\CMS\App_Start\Startup.Auth.cs:line 30

Here is the relevant code from Startup.Auth.cs:

using CMS.Models;
using Microsoft.AspNet.Identity;
using Microsoft.AspNet.Identity.Owin;
using Microsoft.Owin;
using Microsoft.Owin.Security.Cookies;
using Owin;
using System;
using System.Configuration;

namespace CMS
{
    public partial class Startup {

        // For more information on configuring authentication, please visit http://go.microsoft.com/fwlink/?LinkId=301883
        public void ConfigureAuth(IAppBuilder app)
        {
            // Configure the db context, user manager and signin manager to use a single instance per request
            app.CreatePerOwinContext(ApplicationDbContext.Create);
            app.CreatePerOwinContext<ApplicationUserManager>(ApplicationUserManager.Create);
            app.CreatePerOwinContext<ApplicationSignInManager>(ApplicationSignInManager.Create);

            // Enable the application to use a cookie to store information for the signed-in user
            // and to use a cookie to temporarily store information about a user logging in with a third-party login provider
            // Configure the sign-in cookie
            app.UseCookieAuthentication(new CookieAuthenticationOptions
            {
                AuthenticationType = DefaultAuthenticationTypes.ApplicationCookie,
                LoginPath = new PathString("/Account/Login"),
                SlidingExpiration = true,  
                ExpireTimeSpan = TimeSpan.FromMinutes(Double.Parse(ConfigurationManager.AppSettings["CookieExpireTimeSpan"].ToString())),
                Provider = new CookieAuthenticationProvider
                {
                    OnValidateIdentity = SecurityStampValidator.OnValidateIdentity<ApplicationUserManager, ApplicationUser>(
                        validateInterval: TimeSpan.FromMinutes(Double.Parse(ConfigurationManager.AppSettings["CookieExpireTimeSpan"].ToString())),
                        regenerateIdentity: (manager, user) => user.GenerateUserIdentityAsync(manager))
                }
            });
            // Use a cookie to temporarily store information about a user logging in with a third-party login provider
            app.UseExternalSignInCookie(DefaultAuthenticationTypes.ExternalCookie);

            // Enables the application to temporarily store user information when they are verifying the second factor in the two-factor authentication process.
            app.UseTwoFactorSignInCookie(DefaultAuthenticationTypes.TwoFactorCookie, TimeSpan.FromMinutes(5));

            // Enables the application to remember the second login verification factor such as phone or email.
            // Once you check this option, your second step of verification during the login process will be remembered on the device where you logged in from.
            // This is similar to the RememberMe option when you log in.
            app.UseTwoFactorRememberBrowserCookie(DefaultAuthenticationTypes.TwoFactorRememberBrowserCookie);

            // Uncomment the following lines to enable logging in with third-party login providers

            switch (ConfigurationManager.AppSettings["OAuthApp"])
            {
                case "local":
                    app.UseFacebookAuthentication(
                       appId: ConfigurationManager.AppSettings["FacebookLocalAppId"].ToString()
                       , appSecret: ConfigurationManager.AppSettings["FacebookLocalAppSecret"].ToString()
                       );
                    break;
                case "beta":
                    app.UseFacebookAuthentication(
                       appId: ConfigurationManager.AppSettings["FacebookBetaAppId"].ToString()
                       , appSecret: ConfigurationManager.AppSettings["FacebookBetaAppSecret"].ToString()
                       );
                    break;

                case "cms":
                default:
                    app.UseFacebookAuthentication(
                        appId: ConfigurationManager.AppSettings["FacebookCmsAppId"].ToString()
                       , appSecret: ConfigurationManager.AppSettings["FacebookCmsAppSecret"].ToString()
                       );
                    break;
            }

        }
    }
}

Even after downgrading the package back to version 3.6.0, the error persists. Previously, the application ran without issues on version 3.6.0 before the upgrade.

To resolve the issue temporarily, I restored a backup of my website, which restored functionality.

Could anyone advise on what might be causing this error and how to resolve it?

Thanks in advance for your help!

Ruben