How to get RunAs Username in Blazor Server when running a browser using RunAs

Question

When debugging a Razor Server app locally using IISExpress I'm running my application as a test user by starting Chrome (or Edge) using Run As.

How can I get the username of the user that the browser is running as?

public CurrentUser(AuthenticationStateProvider authenticationStateProvider, IWebHostEnvironment webHostEnvironment)
        {
            _webHostEnvironment = webHostEnvironment;
            _authenticationStateProvider = authenticationStateProvider;
        }

        private readonly AuthenticationStateProvider _authenticationStateProvider;
        private readonly IWebHostEnvironment _webHostEnvironment;

        public string UserName
        {
            get
            {                
                if (_webHostEnvironment.IsDevelopment())
                {
                    // return System.Security.Principal.WindowsIdentity.GetCurrent().Name;
                    // return Environment.UserName;
                    return "All return Operating System username";
                }
                else
                {
                    //  returns null when debugging in IIS Express 

                    var authState = Task.Run(_authenticationStateProvider.GetAuthenticationStateAsync).Result;
                    var user = authState.User;
                    var name = user.Identity.Name;

                    return name;
                }

            }
        }