public _NavigationBoxViewModel(Guid id, NavigationBoxType type)
 {
     Id = id;
     Type = type;
     switch(type)
     {
         case NavigationBoxType.Group:
             {
                 var group = DataService.PerThread.GroupSet.SingleOrDefault(x => x.Id == id);
                 if (group != null)
                     Group = new _NavigationBox_GroupViewModel(group);
             }
             break;
         case NavigationBoxType.User:
             {
                 var user = DataService.PerThread.BaseUserSet.OfType<User>().SingleOrDefault(x => x.Id == id);
                 if (user != null)
                     User = new _NavigationBox_UserViewModel(user);
             }
             break;
     }
 }
 public _NavigationBoxViewModel(Group group)
 {
     Id = group.Id;
     Type = NavigationBoxType.Group;
     Group = new _NavigationBox_GroupViewModel(group);
 }