Create roles Identity framework - asp.net-core

Question

I have a problem with creating a role for users. I follow the guide below. https://gooroo.io/GoorooTHINK/Article/17333/Custom-user-roles-and-rolebased-authorization-in-ASPNET-core/32835#.XOBFAcgzbcs
I added the "CreateRoles" method to "Startup.cs"
private async Task CreateRoles(IServiceProvider serviceProvider)
{
//adding custom roles
var RoleManager = serviceProvider.GetRequiredService<RoleManager<IdentityRole>>();
var UserManager = serviceProvider.GetRequiredService<UserManager<IdentityUser>>();
string[] roleNames = { "Admin", "Manager", "Member" };
IdentityResult roleResult;
foreach (var roleName in roleNames)
{
//creating the roles and seeding them to the database
var roleExist = await RoleManager.RoleExistsAsync(roleName);
if (!roleExist)
{
roleResult = await RoleManager.CreateAsync(new IdentityRole(roleName));
}
}
//creating a super user who could maintain the web app
var poweruser = new IdentityUser
{
UserName = Configuration.GetSection("UserSettings")["UserEmail"],
Email = Configuration.GetSection("UserSettings")["UserEmail"]
};
string UserPassword = Configuration.GetSection("UserSettings")["UserPassword"];
var _user = await UserManager.FindByEmailAsync(Configuration.GetSection("UserSettings")["UserEmail"]);
if (_user == null)
{
var createPowerUser = await UserManager.CreateAsync(poweruser, UserPassword);
if (createPowerUser.Succeeded)
{
//here we tie the new user to the "Admin" role
await UserManager.AddToRoleAsync(poweruser, "Admin");
}
}
}
I call it in "Configure":
CreateRoles(serviceProvider).Wait();
When running the application, an exception occurs
AggregateException: One or more errors occurred. (No service for type 'Microsoft.AspNetCore.Identity.RoleManager`1[Microsoft.AspNetCore.Identity.IdentityRole]' has been registered.)
How to fix this?

Answer 1

Append AddRoles to add Role services:
services.AddDefaultIdentity<IdentityUser>()
.AddRoles<IdentityRole>()
.AddDefaultUI(UIFramework.Bootstrap4)
.AddEntityFrameworkStores<ApplicationDbContext>();
Or replace AddDefaultIdentity method with the AddIdentity method in the ConfigureServices method
services.AddIdentity<IdentityUser,IdentityRole>()
.AddDefaultUI(UIFramework.Bootstrap4)
.AddEntityFrameworkStores<ApplicationDbContext>();