IdentityServer4 and ResourceOwnerPasswordValidator Dynamic ConnectionString - authentication

Question

So, IResourceOwnerPasswordValidator is supposed to replace IUserService.
In the old version IdentityServer3 I could do the following:
factory.UserService = new Registration<IUserService>(typeof(MyIdentityUserService));
factory.Register(new Registration<IUserRepository>(userRepository));
which passes a custom userRepository object with the proper connection string.
Now in IdentityServer4 I need to Connect to the proper Portal database in order for ID4 to authenticate the user against the correct portal database.
If I could pass a parameter to the constructor of the ResourceOwnerPasswordValidator class like below , then this would be fine but this is not possible with ASP.NET CORE.
public ResourceOwnerPasswordValidator(string MyConnString)
{
_connstring = MyConnString;
}
This can't work because the ConfigurationService registers this class without the ability to pass values. This makes sense since this registration process begins before the pipeline is built. How do I dynamically pass a connection string to the ResourceOwnerPasswordValidator class? I am trying to authenticate against the portal making the call. In ID3 I could do this by using the acr_value.
I am trying to get ID4 to authenticate as a MultiTenant Authentication Server.

Answer 1

You could inject a service or a DTO into a ResourceOwnerPasswordValidator constructor:
public class ResourceOwnerPasswordValidator : IResourceOwnerPasswordValidator
{
public ResourceOwnerPasswordValidator(IAuthRepository repository)
{
}
}
Hence it is possible to pass a service which returns your connection string.
By default, validator's implementation is registered as Transient which means it will not be a singleton until it is resolved in a singleton (which is not a IdSrv4 case I guess).
If you need a Scoped connection string (i.e. per web request), register a scoped DTO with a factory method: services.AddScoped<T>(() => ) or use AsyncLocal<T>. Check this thread to get more details:
How to Per-Request caching in ASP.net core