What is the best way to update an entity framework model in the database with two instances of a DbContext. For example i have a simple User model which is loaded in one DbContext but saved in another:
User model = null;
using(SampleDbContext dbContext = new SampleDbContext())
{
model = dbContext.User.Find(0);
}
model.UserName = "Test-User";
using(SampleDbContext dbContext = new SampleDbContext())
{
// Here is the place i want to save the changes of the model
// without loading it again from the database and set each property
// ...
dbCotnext.SaveChanges();
}
In my case i want to write some UserManager, which has Create, Update and Delete methods. I think creating one DbContext instance for the howle manager
is no solution, because i only want to save the changes of a specific model.
I also don't want to load the models for updating again from the database and settings each value from the source instance, like:
// Update user
using(SampleDbContext dbContext = new SampleDbContext())
{
// I don't want this:
var model = dbContect.User.Find(0);
model.UserName = sourceModel.UserName;
// ...
dbCotnext.SaveChanges();
}
Maybe my problem with manager classes is very simple, but i could not find any good solution.
P.S.: My manager classes are often singleton classes.
Thank you.
You could in your second DbContext do something like this:
using (SampleDbContext dbContext = new SampleDbContext())
{
dbContext.Entry(model).State = EntityState.Modified;
dbContext.SaveChanges();
}
This would save the changes you have made to the entity to the database. However I can't remember if dbContext.Entry queries the DB for the entity.
Related
I'm trying to keep track of changes to my Asset's properties via the setters in the Asset, which is working.
I then pass this Asset along with its changes:
(Business) Asset
- public string Name...
- public DateTime ChangedDate...
-List<ChangeLogs>
to a method and I'm using AutoMapper to convert it along with its children to an (EntityFramework) Asset; this is working as well.
In my method I
using(var dbContext = new DBContext())
{
// Map our (Business)Asset to our (Entity Framework)Asset
var dataAsset = Mapper.Map<Business.Asset, Data.Asset>(asset);
dbContext.Assets.Attach(asset);
dbCore.SaveChanges();
}
I'm getting this error on the Attach line:
An object with the same key already exists in the ObjectStateManager.
The ObjectStateManager cannot track multiple objects with the same
key.
The believe the key its referring to is my ChangeLog Id (PK).
Is there a way to add multiple ChangeLogs to my Asset and then save it?
When you have a detached entity and try to attach it back that already exists in the context, you will get this exception.
To resolve this, try to load the old entity and save the changes from the new entity.
using(var dbContext = new DBContext())
{
// Map our (Business)Asset to our (Entity Framework)Asset
var dataAsset = Mapper.Map<Business.Asset, Data.Asset>(asset);
var oldEntity = dbContext.Assets.FirstOrDefault(m => m.Id == dataAsset.Id);
dbContext.Entry(oldEntity).CurrentValues.SetValues(dataAsset);
dbContext.Entry(oldEntity.ChangeLogs).CurrentValues.SetValues(dataAsset.ChangeLogs);
dbContext.SaveChanges();
}
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
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 have an Entity with a lot of associated entities which I'm trying to persist using LinqToSql, comming from the NHibernate world i used to create that Entity like this
// UI layer
var entity1 = new Entity1();
entity1.Entity2 = new Entity2 { Id = long.Parse(dropdown.SelectedValue) };
entity1.Entity3 = new Entity3 { Id = long.Parse(dropdown2.SelectedValue) };
...
entity1.List = GetEntities();
...
//DAO layer
public void Insert(Entity1 entity)
{
dataContext.Entity1.InsertOnSubmit(entity);
dataContext.SubmitChanges();
}
when i call the dbContext.SubmitChanges() method in the DAO layer
LinqToSql try to persist also the associated classes, which it has not to do, i know that to solve this problem i have to attach those entities to the current dataContext.
so my question is how do you handle situation like this and what is the best way to persist an object graph using LinqToSql
:
Instansiate the associated classes like the above example and then attach theme to the datacontext
or load theme directly from the database ?
thanks for help.
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.