public void DAO_AttachTest()
{
#region Long term context. It is stored in GenericDAO.Context property
// First we get CommonContext from GenericDAO to check the entity states...
DbContext dbContext = ((GenericDaoEntityFramework <UserProfile, Int64>)userProfileDao).Context;
// 1) We look for an userProfile (it was previously created in MyTestInitialize();
UserProfile user = userProfileDao.Find(userProfile.usrId);
// Check the user is in the context (from Generic DAO) now after the Find() method execution
Assert.AreEqual(dbContext.Entry(user).State, EntityState.Unchanged);
// 2) We are going to delete the previously recovered userProfile
userProfileDao.Remove(user.usrId);
// Check the user is not in the context now (EntityState.Detached notes that entity is not tracked by the context)
Assert.AreEqual(dbContext.Entry(user).State, EntityState.Detached);
// The user was deleted from database
Assert.IsFalse(userProfileDao.Exists(user.usrId));
// 3) So, the user entity is already in memory, but it does not exist neither in the context nor the database.
// Now, if we attach the entity it will be tracked again by the context...
userProfileDao.Attach(user);
// EntityState.Unchanged = entity exists in context and in DataBase with the same values
Assert.AreEqual(dbContext.Entry(user).State, EntityState.Unchanged);
// ... and stored in database too
Assert.IsTrue(userProfileDao.Exists(user.usrId));
#endregion
#region Short Term Context (context is disposed after using{} block)
user = null;
// If we retrieve the user within a short term context it will only be tracked by the local-context
// inside the block. It will not be within the generic context
using (MiniPortalEntities shortTermContext = new MiniPortalEntities())
{
DbSet <UserProfile> userProfiles = shortTermContext.UserProfiles;
user =
(from u in userProfiles
where u.usrId == userProfile.usrId
select u).FirstOrDefault();
Assert.AreEqual(
shortTermContext.ChangeTracker.Entries <UserProfile>().FirstOrDefault().State,
EntityState.Unchanged);
}
// EntityState.Detached notes that entity is not tracked by the context
Assert.AreEqual(dbContext.Entry(user).State, EntityState.Detached);
#endregion
}