I have been stock for 3days now with no possible solution online with this error
System.AggregateException
  HResult=0x80131500
  Message=Some services are not able to be constructed (Error while validating the service descriptor 'ServiceType: Microsoft.AspNetCore.Identity.ISecurityStampValidator Lifetime: Scoped ImplementationType: Microsoft.AspNetCore.Identity.SecurityStampValidator`1[MyTrBox_WebAPI.Model.User]': Unable to resolve service for type 'Microsoft.AspNetCore.Authentication.ISystemClock' while attempting to activate 'Microsoft.AspNetCore.Identity.SecurityStampValidator`1[MyTrBox_WebAPI.Model.User]'.) (Error while validating the service descriptor 'ServiceType: Microsoft.AspNetCore.Identity.ITwoFactorSecurityStampValidator Lifetime: Scoped ImplementationType: Microsoft.AspNetCore.Identity.TwoFactorSecurityStampValidator`1[MyTrBox_WebAPI.Model.User]': Unable to resolve service for type 'Microsoft.AspNetCore.Authentication.ISystemClock' while attempting to activate 'Microsoft.AspNetCore.Identity.TwoFactorSecurityStampValidator`1[MyTrBox_WebAPI.Model.User]'.)
  Source=Microsoft.Extensions.DependencyInjection
  StackTrace:
   at Microsoft.Extensions.DependencyInjection.ServiceProvider..ctor(IEnumerable`1 serviceDescriptors, ServiceProviderOptions options)
   at Microsoft.Extensions.DependencyInjection.ServiceCollectionContainerBuilderExtensions.BuildServiceProvider(IServiceCollection services, ServiceProviderOptions options)
   at Microsoft.Extensions.DependencyInjection.DefaultServiceProviderFactory.CreateServiceProvider(IServiceCollection containerBuilder)
   at Microsoft.Extensions.Hosting.Internal.ServiceFactoryAdapter`1.CreateServiceProvider(Object containerBuilder)
   at Microsoft.Extensions.Hosting.HostBuilder.CreateServiceProvider()
   at Microsoft.Extensions.Hosting.HostBuilder.Build()
   at MyTrBox_WebAPI.Program.Main(String[] args) in C:\Users\Biosec-PC-Samuel\Source\Repos\MyTrBox WebAPI\MyTrBox WebAPI\Program.cs:line 16
Inner Exception 1:
InvalidOperationException: Error while validating the service descriptor 'ServiceType: Microsoft.AspNetCore.Identity.ISecurityStampValidator Lifetime: Scoped ImplementationType: Microsoft.AspNetCore.Identity.SecurityStampValidator`1[MyTrBox_WebAPI.Model.User]': Unable to resolve service for type 'Microsoft.AspNetCore.Authentication.ISystemClock' while attempting to activate 'Microsoft.AspNetCore.Identity.SecurityStampValidator`1[MyTrBox_WebAPI.Model.User]'.
Inner Exception 2:
InvalidOperationException: Unable to resolve service for type 'Microsoft.AspNetCore.Authentication.ISystemClock' while attempting to activate 'Microsoft.AspNetCore.Identity.SecurityStampValidator`1[MyTrBox_WebAPI.Model.User]'.
this is the code I use to add identity in my startup
 var builder = services.AddIdentityCore<User>();
            builder = new IdentityBuilder(
                builder.UserType,
                typeof(UserRole),
                builder.Services);
            builder.AddRoles<UserRole>()
                .AddEntityFrameworkStores<AppDbContext>()
                .AddDefaultTokenProviders()
                .AddSignInManager<SignInManager<User>>();
User class:
public class User : IdentityUser<Guid>
    {
        public string Country { get; set; }
        public DateTimeOffset CreatedAt { get; set; }
    }
UserRole class:
public class UserRole : IdentityRole<Guid>
    {
        public UserRole()
            : base() {
        } 
        public UserRole(string roleName)
            : base(roleName) {
        }
    }
I always run to the above error when I make any call to the API server Thanks in advance
EDIT:
.csproj:
<Project Sdk="Microsoft.NET.Sdk.Web">
  <PropertyGroup>
    <TargetFramework>netcoreapp3.0</TargetFramework>
    <RootNamespace>MyTrBox_WebAPI</RootNamespace>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="AutoMapper" Version="9.0.0" />
    <PackageReference Include="AutoMapper.Extensions.Microsoft.DependencyInjection" Version="7.0.0" />
    <PackageReference Include="Microsoft.AspNetCore.Identity.EntityFrameworkCore" Version="3.0.0" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="3.0.0" />
    <PackageReference Include="Microsoft.Extensions.Logging.Debug" Version="3.0.0" />
    <PackageReference Include="Newtonsoft.Json" Version="12.0.2" />
  </ItemGroup>
</Project>
For customing asp.net core identity, you could follow steps below:
.csproj
<Project Sdk="Microsoft.NET.Sdk.Web">
<PropertyGroup>
    <TargetFramework>netcoreapp3.0</TargetFramework>
</PropertyGroup>
<ItemGroup>
    <PackageReference Include="Microsoft.AspNetCore.Identity.EntityFrameworkCore" Version="3.0.0" />
    <PackageReference Include="Microsoft.AspNetCore.Identity.UI" Version="3.0.0" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="3.0.0" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="3.0.0">
    <PrivateAssets>all</PrivateAssets>
    <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
    </PackageReference>
    <PackageReference Include="Microsoft.Extensions.Logging.Debug" Version="3.0.0" />
    <PackageReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Design" Version="3.0.0" />
</ItemGroup>
</Project>
CoreSecurityContext  
public class CoreSecurityContext : IdentityDbContext<User, UserRole, Guid>
{
    public CoreSecurityContext(DbContextOptions<CoreSecurityContext> options)
        : base(options)
    {
    }
    protected override void OnModelCreating(ModelBuilder builder)
    {
        base.OnModelCreating(builder);
        // Customize the ASP.NET Identity model and override the defaults if needed.
        // For example, you can rename the ASP.NET Identity table names and more.
        // Add your customizations after calling base.OnModelCreating(builder);
    }
}
Startup.cs  
services.AddDefaultIdentity<User>()
        .AddRoles<UserRole>()
        .AddEntityFrameworkStores<CoreSecurityContext>();
 Edward
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