Question

Is there anyway to implement an repository that uses active directory (or any other data source than relational db) as the data source and can get entity objects that has the ability to lazy load their associations?

An example:

Two classes will be frequently used in various applications we are going to develop

class User
{
   public string DisplayName {get; set;}
   public string UserID {get; set;}
   public string Email {get; set;}
   public string WorkPhone {get; set;}
   // etc.
   public string IList<Group> Groups {get; private set;}
   public User Manager {get; set;}
}

class Group
{
   public string DisplayName {get; set;}
   public string Email {get; set;}
   // etc.
   public IList<User> Members {get; private set;}
   public User Owner {get; private set;}
}

I want to be able to reuse these two classes in all our future applications. For some application, the data source for User and Group would now be active directory, but in the future, we may wanna use some database or a mixture of database and active directory. In order for code reuse, I would employ the repository pattern to design two repositories MySqlDBRepository and ActiveDirectoryRepository for me to retrieve and store Users and Groups.

Suppose we already have a library for active directory, which can be used to get user information represented in texts, i.e. you can get user’s name, email, manager id all in string format. I need to implement a repository that can be used in much the same way as Entity framework or NHibernate, i.e.

 var user = _activeDirectoryRepository.GetUserByUserID("bryan");

 foreach(var group in user.Groups) 

     Console.WriteLine(group.Manager.DisplayName);

Most importantly, user.groups and group.Manager both should be lazy-loading automatically. How am I supposed to implement _activeDirectoryRepository.GetUserByUserID("bryan")?

Answer 1

After some thought, I found this solution might be good.

Along with ActiveDirectoryUserRepository, I can create a internal class ProxyUser that inherits from User, which takes a reference to the ActiveDirectoryUserRepository. The ProxyUser should return the Groups property the first time it is invoked.

---

// User.cs
public class User
{
    public virtual string Name { get; set; }
    public virtual string DisplayName {get; set;}
    public virtual string Email { get; set; }

    public virtual IList<Group> Groups { get; set; }
}

---

// Group.cs
public class Group
{
    public virtual string Name { get; set; }
    public virtual string Email { get; set; }

    public virtual IList<User> Members { get; set; }
}

---

//  ProxyUser.cs. It should be in the same assembly as ActiveDirectoryUserRepository 

internal class ProxyUser : User
{

   private ActiveDirectoryUserRepository _repository ;
   internal ProxyUser(ActiveDirectoryUserRepository repository)
   {
       _repository = repository;
   }

   internal string IList<string> GroupNames { get; set; }

   private IList<Group> _groups;
   public override IList<Group> Groups 
   { 
      get
      {
         if (_groups == null)
         {
            if (GroupNames != null && GroupNames.Count > 0)
            {
                _groups = new List<Group>();
                foreach(string groupName in GroupNames)
                   _groups.Add(_repository.FindGroupByName(groupName);
            }
         }
         return _groups;
       }

       set
       {
           _groups = value;
       }
    }
}

---

// ProxyGroup.cs

internal class ProxyGroup : Group
{
    // This class should be similar to ProxyUser
}

---

// ActiveDirectoryUserRepository.cs

public class ActiveDirectoryUserRepository
{
    public User FindUserByName(string name)
    {
         DirectorySearcher searcher = new DirectorySearcher();

         // ...
         // set up the filter and properties of the searcher
         // ...

         Result result = searcher.FindOne();
         User user = new ProxyUser(this)
         {
             Name = result.Properties["displayName"][0],
             Email = result.Properties["email"][0],
             GroupNames = new List<string>()
         };

         foreach(string groupName in result.Properties["memberOf"])
         {
             user.GroupNames.Add(groupName);
         }

         return user;
    }

    public Group FindGroupByName(string name)
    {
        // Find the Group, which should be similar to FindUserByName
    }
}