Login Manager

   Hello,

I am trying to develop an 2tire win forms app. when i login with LoginManager 

Login Manager Code:

public class LoginManager:IEntityLoginManager
    {
        public IPrincipal Login(ILoginCredential pCredential, EntityManager pManager)
        {
            if (pCredential == null)
            {
                throw new AppLoginException(AppLoginExceptionCategory.None,MessageTypes.CreationError);
            }   

            IIdentity identity = new UserIdentity(pCredential.UserName, "Custom", true);
            IPrincipal principal = new UserBase(identity);           

            return principal;
        } 

        public void Logout(IPrincipal principal,EntityManager entityManager)
        {
            SysUser aUser = SysUser.GetUser(entityManager, principal.Identity.Name);

            SysUser.LogoutUser(aUser);
        }
    }

my login code is:

private Boolean DoLogin()
        {            
            try
            {
                var credential = new LoginCredential(UserName.Text.Trim(), UserPassword.Text.Trim(), "Domain");                       
               EntityManager.DefaultManager.Login(credential);                
                return true;
            }
            catch (Exception pException)
            {                
                throw pException;
            }
        }

i am able to login , but when i try to run query on the entity like this

        private GSCostingDBEntities _lmgr = new GSCostingDBEntities(); 
        private BindingList<CucumberPurchaseGrade> Grades { get; set; }   

         Grades = new BindingList<CucumberPurchaseGrade>();

          var query = _lmgr.CucumberPurchaseGrades;
           var results = query.Execute();

            foreach (var item in results)
            {
                Grades.Add(item);
            }
            if(Grades.Count==0)
            {
                AddNewRec();
            }
        }

I get an error saying Unable to login . please let me know what went wrong.

Have a nice day,