Pattern for implementing services

ServicePattern.cs

namespace Domain.Entities
{
  public abstract class EntityBase 
  {
    public abstract bool isValid();
  }
  
  public class Auth : EntityBase
  {
    public string username;
    public string password;
    
    public override bool isValid()
    {
      return !string.isNullOrWhitespace(username) 
        && !string.isNullOrWhitespace(password);
    }
  }
}

namespace Services.Providers
{
  public interface IProvider
  {
    
  }
  
  public abstract class ProviderBase<P> : IProvider
  {
    public abstract P ObjectTool;
    
    public ProviderBase(P ObjectTool)
    {
      this.ObjectTool = ObjectTool;
    }
  }
  
  public class HttpProvider : ProviderBase<HttpClient> 
  {
    public override HttpClient client;
    
    public HttpProvider(HttpClient client)
      : base(client);
    {
      this.client = client;
    }
  }
}

namespace Services
{
  public interface IService 
  {
    
  }
  
  public abstract class ServiceBase<IProvider> : IService
  {
    protected IProvider provider;
    
    public ServiceBase(IProvider provider)
    {
      this.provider = provider;
    }
  }
  
  public interface IAuthService : IService
  {
    Auth authenticate(string username, string password);
  }
  
  public class AuthService : ServiceBase<HttpProvider>, IAuthService
  {
    public override HttpProvider http;
    
    public AuthService(HttpProvider http)
      : super(http)
    {
      this.http = http;
    }
    
    public override Auth authenticate(string username, string password) 
    {
      // call http, do stuffs...
    }
  }
}