I'm hoping this will be an easy one but for the life of me, I cannot find the specific answer elsewhere on SO or any other site.
I have a basic repository/unit of work pattern with Entity Framework Code First. It all works smoothly except for certain cases of Update. THe problem is I have a set of Entity Framework model objects, all prefixed with "Db" which EF returns, but I then convert them to plain DataContract Model objects to pass to the Web layer to give separation of concerns. I have a basic conversion interface that just populates a WebModel object from the DataModel object, copying field by field verbatim.
So if you retrieve a DbUser object from EF with ID of 1, then convert to a User object, then convert that BACK to a DbUser object, you end up with a DbUser with ID of 1, but it is a DIFFERENT object to the one you started with, though they have the same primary key field, the actual CLR objects themselves are different.
The following works
User user;
using (var work = new UnitOfWork())
{
var repository = new UserDataRepository(work);
user = repository.Get(1);
repository.save();
}
var modelUser = DataConverter.Convert(user);
modelUser.Name = "new name";
user = BusinessConverter.Convert(modelUser);
using (var work = new UnitOfWork())
{
var repository = new UserDataRepository(work);
repository.Update(user);
repository.save();
}
As they are using two different unit of works/contexts, so the second block has nothing in the ObjectStateManager to compare to and can just attach the detached object in the Update() methods
This, however does NOT work
using (var work = new UnitOfWork())
{
var repository = new UserDataRepository(work);
user = repository.Get(1);
repository.save();
var modelUser = DataConverter.Convert(user);
modelUser.Name = "new name";
user = BusinessConverter.Convert(modelUser)
repository.Update(user);
repository.save();
}
NOTE: I know logically this doesn't make much sense to convert and just convert back but go with it, I've simplified the example greatly to make it easier to put into paper, in my actual code there is a reason for doing it that way.
I get the usual error "an object with the same key already exists in the objectstatemanager...". I'm assuming because the Get() loads the object into EF and then the update sees that the object is detached, then tries to attach it and it already exists.
My Update method in my repository is as below
public override bool UpdateItem(DbUser item)
{
if (Work.Context.Entry(item).State == EntityState.Detached)
Work.Context.Users.Attach(item);
Work.Context.Entry(item).State = EntityState.Modified;
return Work.Context.Entry(item).GetValidationResult().IsValid;
}
I made this Extension method to the DbContext to ReAttach the Entity without problems try it out:
public static void ReAttach<T>(this DbContext context, T entity) where T : class
{
var objContext = ((IObjectContextAdapter) context).ObjectContext;
var objSet = objContext.CreateObjectSet<T>();
var entityKey = objContext.CreateEntityKey(objSet.EntitySet.Name, entity);
Object foundEntity;
var exists = objContext.TryGetObjectByKey(entityKey, out foundEntity);
// Detach it here to prevent side-effects
if (exists)
{
objContext.Detach(foundEntity);
}
context.Set<T>().Attach(entity);
}
Then just update your method :
public override bool UpdateItem(DbUser item)
{
Work.Context.ReAttach(item);
Work.Context.Entry(item).State = EntityState.Modified;
return Work.Context.Entry(item).GetValidationResult().IsValid;
}
You might get a manged Entity, and again verbatim map the new DbUser's properties to the managed Object:
public override bool UpdateItem(DbUser item)
{
using (var work = new UnitOfWork())
{
var repository = new UserDataRepository(work);
DbUser managedUser = repository.Get(item.PK);
//foreach DbUser property map the item to managedUser
managedUser.field1 = item.field1;
[..]
repository.Update(managedUser);
repository.Save();
}
}
If you set your context to AsNoTracking() this will stop aspmvc tracking the changes to the entity in memory (which is what you want anyway on the web).
_dbContext.Products.AsNoTracking().Find(id);
I would recommend you read more about this at http://www.asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/advanced-entity-framework-scenarios-for-an-mvc-web-application
Yash
Related
I got update method that updates only the entity without its children
public void Update(T obj)
{
Ensure.IsNull(obj);
using (var DB = AccessManager.db)
{
DB.Set<T>().Attach(obj);
DB.Entry(obj).State = System.Data.EntityState.Modified;
DB.SaveChanges();
}
}
I try to update
LessonModel.Title = "Updated";
LessonModel.Files.Add(new LessonFileModel { IdxNumber = LessonModel.IdxNumber, FileName = "asd", FilePath = " asdf" });
DALFacade.Lesson.Update(LessonModel);
Only the title gets updated. The files are not updated.
So if the method like this:
public void Update(LessonModel obj)
{
Ensure.IsNull(obj);
using (var DB = AccessManager.db)
{
DB.Lessons.Attach(obj);
DB.Entry(obj).State = System.Data.EntityState.Modified;
DB.SaveChanges();
}
}
How can i save the child?
This is one of the problems that arise when you use the "Generic Repository" anti pattern. Writing an Update method that works for every combination of entity graphs that you pass in and will always do exactly what you want it to do is a big pain in the EF.
Instead, try writing repositories that match your use cases.
Your current problem could be solved if you added the files to the lesson after you attached it to the context. Marking an entry as modified marks all properties on this entry as modified, it doesn't affect relationships.
I am writing a asp.net mvc4 app and I am using entity framework 5. Each of my entities have fields like EnteredBy, EnteredOn, LastModifiedBy and LastModifiedOn.
I am trying to auto-save them by using the SavingChanges event. The code below has been put together from numerous blogs, SO answeres etc.
public partial class myEntities : DbContext
{
public myEntities()
{
var ctx = ((IObjectContextAdapter)this).ObjectContext;
ctx.SavingChanges += new EventHandler(context_SavingChanges);
}
private void context_SavingChanges(object sender, EventArgs e)
{
ChangeTracker.DetectChanges();
foreach (ObjectStateEntry entry in
((ObjectContext)sender).ObjectStateManager
.GetObjectStateEntries
(EntityState.Added | EntityState.Modified))
{
if (!entry.IsRelationship)
{
CurrentValueRecord entryValues = entry.CurrentValues;
if (entryValues.GetOrdinal("LastModifiedBy") > 0)
{
HttpContext currContext = HttpContext.Current;
string userName = "";
DateTime now = DateTime.Now;
if (currContext.User.Identity.IsAuthenticated)
{
if (currContext.Session["userId"] != null)
{
userName = (string)currContext.Session["userName"];
}
else
{
userName = currContext.User.Identity.Name;
}
}
entryValues.SetString(
entryValues.GetOrdinal("LastModifiedBy"), userName);
entryValues.SetDateTime(
entryValues.GetOrdinal("LastModifiedOn"), now);
if (entry.State == EntityState.Added)
{
entryValues.SetString(
entryValues.GetOrdinal("EnteredBy"), userName);
entryValues.SetDateTime(
entryValues.GetOrdinal("EnteredOn"), now);
}
else
{
string enteredBy =
entry.OriginalValues.GetString(entryValues.GetOrdinal("EnteredBy"));
DateTime enteredOn =
entry.OriginalValues.GetDateTime(entryValues.GetOrdinal("EnteredOn"));
entryValues.SetString(
entryValues.GetOrdinal("EnteredBy"),enteredBy);
entryValues.SetDateTime(
entryValues.GetOrdinal("EnteredOn"), enteredOn);
}
}
}
}
}
}
My problem is that entry.OriginalValues.GetString(entryValues.GetOrdinal("EnteredBy")) and entry.OriginalValues.GetDateTime(entryValues.GetOrdinal("EnteredOn")) are not returning the original values but rather the current values which is null. I tested with other fields in the entity and they are returning the current value which were entered in the html form.
How do I get the original value here?
I think the problem may be that you are using the instance provided by the model binder as the input to your controller method, so EF does not know anything about that entity and its original state. Your code may look like this:
public Review Update(Review review)
{
_db.Entry(review).State = EntityState.Modified;
_db.SaveChanges();
return review;
}
In that case, EF knows nothing about the Review instance that is being saved. It is trusting you and setting it as modified, so it will save all of its properties to the database, but it does not know the original state\values of that entity.
Check the section named Entity States and the Attach and SaveChanges Methods of this tutorial. You can also check the first part of this article, that shows how EF does not know about the original values and will update all properties in the database.
As EF will need to know about the original properties, you may first load your entity from the database and then update its properties with the values received in the controller. Something like this:
public Review Update(Review review)
{
var reviewToSave = _db.Reviews.SingleOrDefault(r => r.Id == review.Id);
//Copy properties from entity received in controller to entity retrieved from the database
reviewToSave.Property1 = review.Property1;
reviewToSave.Property2 = review.Property2;
...
_db.SaveChanges();
return review;
}
This has the advantage that only modified properties will be send and updated in the database and that your views and view models don't need to expose every field in your business objects, only those that can be updated by the users. (Opening the door for having different classes for viewModels and models\business objects). The obvious disadvantage is that you will incur an additional hit to the database.
Another option mentioned in the tutorial I referenced above is for you to save the original values somehow (hidden fields, session, etc) and on save use the original values to attach the entity to the database context as unmodified. Then update that entity with the edited fields. However I would not recommend this approach unless you really need to avoid that additional database hit.
Hope that helps!
I was running into a similar problem when trying to audit log the Modified values of an Entity.
It turns out during the post back the ModelBinder doesn't have access to the original values so the Model received is lacking the correct information. I fixed my problem by using this function which clones the current values, relods the object, and then reset the current values.
void SetCorrectOriginalValues(DbEntityEntry Modified)
{
var values = Modified.CurrentValues.Clone();
Modified.Reload();
Modified.CurrentValues.SetValues(values);
Modified.State = EntityState.Modified;
}
You can gain access to the DbEntityEntry though the change tracker, or the entry function from your context.
My Database is set up with an Entity table, which has a Ref_Type navigation property (and a FK which references TypeID). The Type table, has a Ref_Department, same FK setup. Finally, the Department table has a Ref_Locale and same FK setup.
I save the Entities in a List, which is a property of a singleton. It is created as follows;
private Singleton()
{
using (Database db = new Database())
{
List<Entities> EntityList = db.Entities.ToList<Entities>();
}
}
This is fine, the navigation properties are ALL loaded and I can access any one of them.
The problem comes when I update an Entity entry as follows;
public void UpdateEntity(Entities oldEnt, Entities newEnt)
{
using (Database db = new Database())
{
Entities ent = db.Entities.Where(e => e.EntityName == oldEnt.EntityName).FirstOrDefault();
ent.EntityName = newEnt.EntityName;
ent.EntityEmail = newEnt.EntityEmail;
...
ent.EntityType_ID = newEnt.EntityType_ID;
db.SaveChanges();
}
RefreshEntities();
}
public void RefreshEntities()
{
using (Database db = new Database())
{
db.Configuration.LazyLoadingEnabled = false;
db.SaveChanges();
EntityList = db.Entities.Include("Ref_EntityType").Include("Ref_EntityPosition").ToList<Entities>();
}
}
Ref_Entity gets loaded properly, but then within Ref_Entity, Ref_Department is just null. I've tried just using db.Entities.ToList<Entities>(); like in my constructor, no dice. As you can see, I've also tried turning LazyLoading off (I thought I might need to call SaveChanges() for it to actually apply the flag). I've also tried .Include("Ref_Department") but it just complains that it doesn't exist for Entities, which makes sense.
The newEnt that I pass to the UpdateEntity method does not have Ref_Type initialised, I'm working under the assumption that anything not changed in the UpdateEntity method would just stay the same...
So now I'm at a bit of a loss as to what's going on and how to fix it. If anyone could help explain where I'm going wrong or give me some pointers about how to fix my code to make it work, that would be great.
On a whim, I modified RefreshEntities() to;
EntityList = db.Entities.Include("Ref_EntityPosition").Include("Ref_EntityType").
Include("Ref_EntityType.Ref_Department").
Include("Ref_EntityType.Ref_Department.Ref_Locale").ToList<Entities>();
And now I'm getting all the references.
I'm still not sure why it would load all the references in the constructor but not in the RefreshEntities() method, even if the calls are identical, but this solves the problem so I'm happy enough to leave it like that.
I've read through at least a dozen other questions just like this one, but I am having trouble grasping some of this stuff.
I'm used to developing ASP.NET MVC3 with repositories and code-first entities linking to the entity framework.
I've recently switched to database-first ADO.NET with services development.
I find this to be very clean since I can access stuff through my foreign keys.
Anyway, my old save methods seem to be broken since I constantly get this error
An entity object cannot be referenced by multiple instances of
IEntityChangeTracker
So here's a look at my save action and my service:
Action:
[HttpPost]
public ActionResult AddReview(Review review, int id)
{
User loggedInUser = userService.GetUserByusername(User.Identity.Name);
review.WriterId = loggedInUser.UserId;
review.ProductId = id;
if (ModelState.IsValid)
{
reviewService.Save(review);
Product product = productService.GetProduct(id);
if(product.Quantity>=1)
product.Quantity--;
product.TimesBought++;
productService.UpdateRating(product, reviewService);
loggedInUser.GoldCoins -= product.Price;
Session["goldCoins"] = loggedInUser.GoldCoins;
userService.Save(loggedInUser);
productService.Save(product);
}
else
{
return View(review);
}
return RedirectToAction("Index", "Answers", new { reviewId = review.ReviewId });
Service:
public class ReviewService : Service<Review, CapstoneEntities>
{
...
public void Save(Review review)
{
using (var db = new CapstoneEntities())
{
if (review.ReviewId == 0)
{
db.Reviews.Add(review);
db.Entry(review).State = EntityState.Added;
}
else
{
db.Entry(review).State = EntityState.Modified;
}
db.SaveChanges();
}
}
}
My suspicion is with this line of code: using (var db = new CapstoneEntities()) but I'm not sure how else to do this. Again, this worked perfectly with my old way of doing things but now I get errors on just about ever CRUD operation.
Thank you.
It looks like this is being caused by having an entity belong to multiple DataContexts. Whatever code that is calling that action should use the same DataContext to create the entity as the one used to persist it to the datastore.
In most instances you should only keep one instance of the DataContext. You can use a DI framework like Castle to define/store a dependency (in this case the DataContext) as Transient or PerWebRequest and inject it into the service and controller, so you'll always have a reference to the same instance of the DataContext.
I am new to MVC & Entity frame work. I got same problem after fighting a lot
This solution worked for me. Hope it can be useful for you guys.
var mediaItem = db.MediaItems.FirstOrDefault(x => x.Id == mediaItemViewModel.Id);
mediaItem.Name = mediaItemViewModel.Name;
mediaItem.Description = mediaItemViewModel.Description;
mediaItem.ModifiedDate = DateTime.Now;
mediaItem.FileName = mediaItem.FileName;
mediaItem.Size = KBToMBConversion(mediaItemViewModel.Size);
mediaItem.Type = mediaItem.Type;
//db.Entry(mediaItem).State = EntityState.Modified;// coment This line
db.SaveChanges();
Cause you are reading the the whole object from db and holding it in the current context and when you try to modify the entity state its tells you already one entity attached to the current context. just call save changes it will save it.
I'm new to Entity Framework (working mostly with NHibernate with ActiveRecord before) and I'm stuck with something, that I think should be easy...
I have a User Entity, and created partial User class so I can add some methods (like with NHibernate). I added GetByID to make getting user easier:
public static User GetByID(int userID)
{
using (var context = new MyEntities())
{
return context.Users.Where(qq => qq.UserID == userID).Single();
}
}
Now in the same class I want to log moment of logging in, and I try to do:
public static void LogLoginInfo(int userID)
{
using (var context = new MyEntities())
{
var user = User.GetByID(userID);
var log = new LoginLog { Date = DateTime.Now };
user.LoginLogs.Add(log);
context.SaveChanges();
}
}
The problem is I can't access user.LoginLogs because user's context is already disposed... Most likely I'm missing something obvious here, but creating always full queries like:
context.Users.Where(qq => qq.UserID == userID).Single().LoginLogs.Add(log);
doesn't seem like a good option...
I've read about Repository pattern but I think it's too big gun for such task. Please explain me what am I doing wrong. Thanks in advance!
EDIT
To picture what I'd like to do:
//somewhere in business logic
var user = User.GetByID(userID);
var posts = user.GetAllPostsForThisMonth();
foreach(var post in posts)
{
Console.WriteLine(post.Answers.Count);
}
Normally I'm not allowed to do this because I can't get post.Answers without context...
You are closing the object context and then trying to add a log to the user that is detached. You need to attach the user so the objectContext know what has been changed or added.
public static void LogLoginInfo(int userID)
{
using (var context = new MyEntities())
{
var user = context.User.Where(p=>p.UserID == userID); //<= The Context now knows about the User, and can track changes.
var log = new LoginLog { Date = DateTime.Now };
user.LoginLogs.Add(log);
context.SaveChanges();
}
}
Update
You can also attach the object.
public static void LogLoginInfo(int userID)
{
using (var context = new MyEntities())
{
var user = User.GetByID(userID);
var log = new LoginLog { Date = DateTime.Now };
user.LoginLogs.Add(log);
context.User.Attach(user);
context.SaveChanges();
}
}
Update
var getFirstLogin = from p in User.GetUserById(userId)
select p.LoginLogs.FirstOrDefault();
NB if LoginLogs is a different table you will need to use Include.
public static User GetByID(int userID)
{
using (var context = new MyEntities())
{
return context.Users.Include("LoginLogs").Where(qq => qq.UserID == userID).FirstOrDefault();
}
}
If you are open to using stored procedures (and they work nicely with EF), you can return the user object and simultaneously add to the log table with a single call to the database.
I used to do everything with SP's in my pre-EF/ORM days, when I went to EF I tried very hard to avoid using stored procedures to avoid falling back into my old habits, but now I have found that the selective use of stored procedures you can have the benefits of both -the EF way of doing things, and the super functionality/performance that a well written SP can provide.