ASP.NET API - Unable to create a DbContext

Question

I am learning ASP.NET

I tried the following code to enable IdentityCore on my API with AddRole

builder.Services.AddIdentityCore<User>()
.AddRoles<IdentityRole>()
.AddEntityFrameworkStores<AppDbContext>()
.AddDefaultTokenProviders()
.AddApiEndpoints();

...

app.MapIdentityApi<User>();

...

public class AppDbContext : IdentityDbContext<User> { ...

public class User : IdentityUser
{

    
}

These are the codes that i have used.
Before adding the AddIdentityCore, Everything was working. I was able to connect with the Db

builder.Services.AddDbContext<AppDbContext>(options => options.UseNpgsql(builder.Configuration.GetConnectionString("PgDatabase")));

An error occurred while accessing the Microsoft.Extensions.Hosting services. Continuing without the application service provider. Error: Some services are not able to be constructed (Error while validating the service descriptor 'ServiceType: Microsoft.AspNetCore.Identity.DataProtectorTokenProvider`1[backend.Models.User] Lifetime: Transient ImplementationType: Microsoft.AspNetCore.Identity.DataProtectorTokenProvider`1[backend.Models.User]': Unable to resolve service for type 'Microsoft.AspNetCore.DataProtection.IDataProtectionProvider' while attempting to activate 'Microsoft.AspNetCore.Identity.DataProtectorTokenProvider`1[backend.Models.User]'.)


Unable to create a 'DbContext' of type 'backend.Database.AppDbContext'. The exception 'Unable to resolve service for type 'Microsoft.EntityFrameworkCore.DbContextOptions' while attempting to activate 'backend.Database.AppDbContext'.' was thrown while attempting to create an instance. For the different patterns supported at design time, see https://go.microsoft.com/fwlink/?linkid=851728

Answer 1

Hi @Mahesh Kumar

builder.Services.AddIdentityCore<User>() .AddRoles<IdentityRole>() .AddEntityFrameworkStores<AppDbContext>() .AddDefaultTokenProviders() .AddApiEndpoints();

The issue relates the above code, incorrect Identity configuration. When I try to use the above code and enable migration, I could reproduce the problem:

To solve this issue, you can try to modify the code as below:

builder.Services.AddIdentity<User, IdentityRole>()
                .AddEntityFrameworkStores<AppDbContext>()
                .AddDefaultTokenProviders()
                .AddApiEndpoints();

Besides, if you want to use the AddRoles method to configurate Identity Role, you can use it with AddIdentityApiEndpoints<IdentityUser> or AddDefaultIdentity<IdentityUser>(), code like this:

builder.Services.AddIdentityApiEndpoints<User>()
    .AddRoles<IdentityRole>()
    .AddEntityFrameworkStores<AppDbContext>();

or

builder.Services.AddDefaultIdentity<User>()
                .AddRoles<IdentityRole>()
                .AddEntityFrameworkStores<AppDbContext>()
                .AddDefaultTokenProviders()
                .AddApiEndpoints();

Note: The preceding code requires the Microsoft.AspNetCore.Identity.UI package and a using directive for Microsoft.AspNetCore.Identity. Generally, ASP.NET Core Identity UI is the default Razor Pages built-in UI for the ASP.NET Core Identity framework, and we will use the Microsoft.AspNetCore.Identity.UI package in the Razor Page or MVC application.

The above codes work well on my side. After migration, the database generated successfully. You can check them.

More detail information, see:

Identity model customization in ASP.NET Core

Role-based authorization in ASP.NET Core

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Best regards,

Dillion