I am having difficulties figuring out how to implement roles in an ASP.Net MVC app. I am relatively new to the framework, and I just can't figure this one out. My DbInitializer class is called in a Try/Catch block in Program.cs, and is failing at:

 var roleManager = services .GetRequiredService<RoleManager<IdentityRole>>(); 

throwing the error "InvalidOperationException: No service for type 'Microsoft.AspNetCore.Identity.RoleManager`1[Microsoft.AspNetCore.Identity.IdentityRole]' has been registered." I had to remove the Try/Catch block and just run DbInitializer.Initialize() outside of it to produce the error.

Startup.cs:

using System; using System.Collections.Generic; using System.Linq; using System.Threading.Tasks; using Microsoft.AspNetCore.Builder; using Microsoft.AspNetCore.Identity; using Microsoft.AspNetCore.Hosting; using Microsoft.AspNetCore.Http; using Microsoft.AspNetCore.HttpsPolicy; using Microsoft.AspNetCore.Mvc; using Microsoft.EntityFrameworkCore; using ClevelandTeaRevival.Data; using Microsoft.Extensions.Configuration; using Microsoft.Extensions.DependencyInjection; namespace ClevelandTeaRevival { 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.Configure<CookiePolicyOptions>(options => { // This lambda determines whether user consent for non-essential cookies is needed for a given request. options.CheckConsentNeeded = context => true; options.MinimumSameSitePolicy = SameSiteMode.None; }); services.AddDbContext<ApplicationDbContext>(options => options.UseSqlServer( Configuration.GetConnectionString("DefaultConnection"))); services.AddDefaultIdentity<IdentityUser>() .AddEntityFrameworkStores<ApplicationDbContext>(); services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1); } // This method gets called by the runtime. Use this method to configure the HTTP request pipeline. public void Configure(IApplicationBuilder app, IHostingEnvironment env) { if (env.IsDevelopment()) { app.UseDeveloperExceptionPage(); app.UseDatabaseErrorPage(); } else { app.UseExceptionHandler("/Home/Error"); app.UseHsts(); } app.UseHttpsRedirection(); app.UseStaticFiles(); app.UseCookiePolicy(); app.UseAuthentication(); app.UseMvc(routes => { routes.MapRoute( name: "default", template: "{controller=Home}/{action=Index}/{id?}"); }); } } } 

Program.cs:

using System; using System.Collections.Generic; using System.IO; using System.Linq; using System.Threading.Tasks; using ClevelandTeaRevival.Data; using Microsoft.AspNetCore; using Microsoft.AspNetCore.Hosting; using Microsoft.Extensions.Configuration; using Microsoft.Extensions.DependencyInjection; using Microsoft.Extensions.Logging; namespace ClevelandTeaRevival { public class Program { public static void Main(string[] args) { // CreateWebHostBuilder(args).Build().Run(); var host = CreateWebHostBuilder(args).Build(); using (var scope = host.Services.CreateScope()) { var services = scope.ServiceProvider; try { // var context = services.GetRequiredService<ApplicationDbContext>(); DbInitializer.Initialize(services, context).Wait(); } catch (Exception ex) { var logger = services.GetRequiredService<ILogger<Program>>(); logger.LogError(ex, "An error occurred while seeding the database."); } } host.Run(); } public static IWebHostBuilder CreateWebHostBuilder(string[] args) => WebHost.CreateDefaultBuilder(args) .UseStartup<Startup>(); } } 

DbInitializer.cs:

using System; using System.Collections.Generic; using System.Linq; using System.Threading.Tasks; using ClevelandTeaRevival.Models; using Microsoft.AspNetCore.Identity; using Microsoft.EntityFrameworkCore; using Microsoft.Extensions.DependencyInjection; namespace ClevelandTeaRevival.Data { public static class DbInitializer { public static async Task Initialize(IServiceProvider services, ApplicationDbContext _context) { //========================== var roleManager = services .GetRequiredService<RoleManager<IdentityRole>>(); await EnsureRolesAsync(roleManager); //========================== var userManager = services .GetRequiredService<UserManager<IdentityUser>>(); await EnsureTestAdminAsync(userManager); //========================== _context.Database.EnsureCreated(); //Look for any customers if (_context.Teas.Any()) { return; //customers found, db has already been seeded } var administrators = new Administrator[] { new Administrator{FirstName="Amber", LastName="A"}, new Administrator{FirstName="Mike", LastName="M"} }; foreach( Administrator a in administrators) { _context.Admin.Add(a); } _context.SaveChanges(); var customers = new Customer[] { new Customer{FirstName="Carson",LastName="Alexander",MailingAddress="123 Fake Street, Cleveland, OH, 44108, U.S.A."}, new Customer{FirstName="Meredith",LastName="Alonso",MailingAddress="666 Satan Lane, Hot Town, FL, Luciferia"}, new Customer{FirstName="Arturo",LastName="Anand",MailingAddress="999 Rancid Road, , Los Angeles, CA, U.S.A." }, new Customer{FirstName="Gytis",LastName="Barzdukas",MailingAddress="filler address"}, new Customer{FirstName="Yan",LastName="Li",MailingAddress="filler address"}, new Customer{FirstName="Peggy",LastName="Justice",MailingAddress="filler address"}, new Customer{FirstName="Laura",LastName="Norman",MailingAddress="filler address"}, new Customer{FirstName="Nino",LastName="Olivetto",MailingAddress="filler address"} }; foreach (Customer c in customers) { _context.Customers.Add(c); } _context.SaveChanges(); var blogPosts = new BlogPost[] { new BlogPost{Title="Yes Kombucha", Text="Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris"}, new BlogPost{Title="No Kombucha", Text="Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris"}, new BlogPost{Title="Yes Kombucha", Text="Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris"}, new BlogPost{Title="No Kombucha", Text="Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris"}, new BlogPost{Title="Yes Kombucha", Text="Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris"} }; foreach (BlogPost bp in blogPosts) { _context.BlogPosts.Add(bp); } _context.SaveChanges(); var events = new Event[] { new Event{EventName="Kombucha Class", EventDate=DateTime.Parse("2018-09-27")}, new Event{EventName="Kombucha Class", EventDate=DateTime.Parse("2018-10-20")}, }; foreach (Event e in events) { _context.Events.Add(e); } _context.SaveChanges(); var foodItems = new FoodItem[] { new FoodItem{Name="Toast", Price=5.55m}, new FoodItem{Name="Salad Bowl", Price=8} }; foreach (FoodItem fi in foodItems) { _context.FoodItems.Add(fi); } _context.SaveChanges(); var teas = new Tea[] { new Tea{Name="Silver Needles", Category ="White Teas", PricePerCup =4.5m, PricePerPot =5.5m, PricePerOz =8, Description ="China – light honey, floral umami finish"}, new Tea{Name="Peony", Category="White Teas", PricePerCup=3, PricePerPot=5, PricePerOz=6, Description="China – cooling nectarine flavor, mild hay"}, new Tea{Name="Jasmine Pearl", Category="Green Teas", PricePerCup=4.5m, PricePerPot=5.5m, PricePerOz=11, Description="China – jasmine infused green tea pearls"}, new Tea{Name="Dragonwell", Category="Green Teas", PricePerCup=4, PricePerPot=5.5m, PricePerOz=9, Description="China – pan cooked, bright, sweet & savory finish"}, new Tea{Name="Gunpowder", Category="Green Teas", PricePerCup=3, PricePerPot=5, PricePerOz=6, Description="China – medium roast, charcoal, honey"}, new Tea{Name="Jade Cloud", Category="Green Teas", PricePerCup=3.5m, PricePerPot=5, PricePerOz=6, Description="China – sweet cream, grassy"}, new Tea{Name="Gaba Green", Category="Green Teas", PricePerCup=5.5m, PricePerPot=6.5m, PricePerOz=12, Description="Taiwan – velvety, herbaceous"}, new Tea{Name="Genmaicha", Category="Green Teas", PricePerCup=3.5m, PricePerPot=5, PricePerOz=6, Description="Japan – steamed with brown rice, toasted, oceanic"}, new Tea{Name="Genmai Matcha", Category="Green Teas", PricePerCup=3, PricePerPot=5, PricePerOz=6, Description="Japan – steamed with brown rice, tossed in matcha, bright vegetal"}, new Tea{Name="Gyokuro", Category="Green Teas", PricePerCup=5.5m, PricePerPot=6, PricePerOz=12, Description="Japan – umami, oceanic, spring"}, new Tea{Name="Kukicha", Category="Green Teas", PricePerCup=4, PricePerPot=5, PricePerOz=6, Description="Japan – bright, sweet flavor"}, new Tea{Name="Sencha", Category="Green Teas", PricePerCup=3.5m, PricePerPot=5, PricePerOz=7, Description="Japan – grassy, vegetal"}, new Tea{Name="Sencha Infused With Matcha", Category="Green Teas", PricePerCup=4.5m, PricePerPot=5.5m, PricePerOz=7.5m, Description="Japan – grassy, tossed in matcha"}, new Tea{Name="Matcha", Category="Green Teas", PricePerCup=3.5m, PricePerPot=5.5m, PricePerOz=16, PricePerLb=30, Description="Japan"} }; foreach (Tea tea in teas) { _context.Teas.Add(tea); } _context.SaveChanges(); } private static async Task EnsureRolesAsync( RoleManager<IdentityRole> roleManager) { var alreadyExists = await roleManager .RoleExistsAsync(Constants.AdministratorRole); if (alreadyExists) return; await roleManager.CreateAsync( new IdentityRole(Constants.AdministratorRole)); } private static async Task EnsureTestAdminAsync( UserManager<IdentityUser> userManager) { var testAdmin = await userManager.Users .Where(x => x.UserName == "amber@tootmail.com") .SingleOrDefaultAsync(); if (testAdmin != null) return; testAdmin = new IdentityUser { UserName = "amber@tootmail.com", Email = "amber@tootmail.com" }; await userManager.CreateAsync( testAdmin, "R@m0n@"); await userManager.AddToRoleAsync( testAdmin, Constants.AdministratorRole); } } }