.Net Core Inject UserManager Without AddIdentity

Question

I want to use usermanager methods without add identity to whole project.Because my application already uses an authentication that is not identity. I just want to connect db and insert user via usermanager. But when i use it like this got di error.

Builder.cs

builder.Services.AddDbContext<CustomIdentityDbContext>(opt => { opt.UseSqlServer(builder.Configuration.GetConnectionString("SomeDb")); });

builder.Services.AddScoped<UserManager<CustomIdentityUser>>();

Service and injection:

   private readonly UserManager<CustomIdentityUser> _userManager;

    public TenantController(UserManager<CustomIdentityUser> userManager)
    {
        _userManager = userManager;
    }

Answer 1

Because my application already uses an authentication that is not identity. I just want to connect db and insert user via usermanager.

Sounds like you want a pure solution that doesn't regist Identity related Authentication Schemes

Then let us check the source codes of AddDefaultIdentity:

public static IdentityBuilder AddDefaultIdentity<TUser>(this IServiceCollection services, Action<IdentityOptions> configureOptions) where TUser : class
    {
        services.AddAuthentication(o =>
        {
            o.DefaultScheme = IdentityConstants.ApplicationScheme;
            o.DefaultSignInScheme = IdentityConstants.ExternalScheme;
        })
        .AddIdentityCookies(o => { });

        return services.AddIdentityCore<TUser>(o =>
        {
            o.Stores.MaxLengthForKeys = 128;
            configureOptions?.Invoke(o);
        })
            .AddDefaultUI()
            .AddDefaultTokenProviders();
    }

You could see AddIdentityCore method is the possible solution for you

Then Let's check the codes inside AddIdentityCore method:

public static IdentityBuilder AddIdentityCore<TUser>(this IServiceCollection services, Action<IdentityOptions> setupAction)
        where TUser : class
    {
        // Services identity depends on
        services.AddOptions().AddLogging();

        // Services used by identity
        services.TryAddScoped<IUserValidator<TUser>, UserValidator<TUser>>();
        services.TryAddScoped<IPasswordValidator<TUser>, PasswordValidator<TUser>>();
        services.TryAddScoped<IPasswordHasher<TUser>, PasswordHasher<TUser>>();
        services.TryAddScoped<ILookupNormalizer, UpperInvariantLookupNormalizer>();
        services.TryAddScoped<IUserConfirmation<TUser>, DefaultUserConfirmation<TUser>>();
        // No interface for the error describer so we can add errors without rev'ing the interface
        services.TryAddScoped<IdentityErrorDescriber>();
        services.TryAddScoped<IUserClaimsPrincipalFactory<TUser>, UserClaimsPrincipalFactory<TUser>>();
        services.TryAddScoped<UserManager<TUser>>();

        if (setupAction != null)
        {
            services.Configure(setupAction);
        }

        return new IdentityBuilder(typeof(TUser), services);
    }

It adds plenty of services into Identity builder,when IServiceCollection was build,it would regist required service for you,that why you got DI error when you just try withbuilder.Services.AddScoped<UserManager<CustomIdentityUser>>();

Now,inject IAuthenticationSchemeProvider into PageModel and check the registed Authentication schemes with _authenticationSchemeProvider.GetAllSchemesAsync()

When I try with default Identity,4 schemes were registed:

When I try with

builder.Services.AddIdentityCore<AppUser>().AddEntityFrameworkStores<IdentityTestContext>();

No Authentication scheme was registed and a record was created successfully in Database