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.
Related
I'm using EF with WEB API.
I have a PUT Method which updates a entity which already is in the db.
Right now I have this:
// PUT api/fleet/5
public void Put(Fleet fleet)
{
Fleet dbFleet = db.Fleets.Find(fleet.FleetId);
dbFleet.Name = fleet.Name;
dbFleet.xy= fleet.xy;
//and so on....
db.SaveChanges();
}
But I'm lazy and would just like to write something like:
dbFleet.update(fleet);
So I don't have to update every property by its own.
I'm sure there is a way but I could only find answers on how to do this with MVC but not when using a WEB API and not receiving the model state.
Thanks
db.Fleets.Attach(fleet);
db.Entry(fleet).State = EntityState.Modified;
db.SaveChanges();
Just found the answer...
// PUT api/fleet/5
public void Put(Fleet fleet)
{
db.Entry(fleet).State = EntityState.Modified;
db.SaveChanges();
}
Only thing I'm not happy with is that it doesn't update child object.
Fleet has FleetAttributes which are not updated like this. But I guess I can easily loop them...
EDIT this works for me:
// PUT api/fleet/5
public void Put(Fleet fleet)
{
db.Entry(fleet).State = EntityState.Modified;
foreach (var item in fleet.FleetAttributes)
{
db.Entry(item).State = EntityState.Modified;
}
db.SaveChanges();
}
When I try to update my entry in update function it's execute successfully but database not updated.
Please find the following code
public static string UpdateEmployee(Employee employee)
{
using (var db = new RandDEntities())
{
var empObj = db.Employees.First(x => x.EmpID == employee.EmpID);
db.Entry(empObj).State = EntityState.Modified;
db.SaveChanges();
}
return "";
}
The problem is that you're saving the wrong entity (i.e. empObj) instead of the entity that has the changes (i.e. employee). Your code pulls empObj out of the database, and then turns around and saves it, without making any changes to it. You need to modify your code as follows:
public static string UpdateEmployee(Employee employee)
{
using (var db = new RandDEntities())
{
db.Employees.Attach(employee);
db.Entry(employee).State = EntityState.Modified;
db.SaveChanges();
}
return "";
}
That has absolutely nothing to do with Entity Framework but more with the fact that you likely use localdb and your database is not where you think it is, and reinitialized (reset) to empty every time you press start.
This question, in dozens of variants, gets asked over and overy by people not bothering to check where they look (and then realizing the database files have different paths).
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
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.
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.