As you can see from the code below i use AsNoTracking to get my object.
I then even use ObjectSateManager to see what is going on and i can see
nothing being tracked in the l* collections and yet i still get
"An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key".
Any ideas?
==========================================
BasketRepository repo = new BasketRepository();
var ba = repo.GetById(8);
var bpro = new BasketProduct(ba, ba.BasketProducts.First().Product, 3);
repo.AddToBasket(bpro);
repo.Save();
==================================
public Basket GetById(int basketId)
{
// eager-load product info
var basket = dbContext.Baskets.Include("BasketProducts")
.Include("BasketProducts.Product.Brand").AsNoTracking().SingleOrDefault(b => b.BasketId == basketId);;
return basket;
}
======================================
public void AddToBasket(BasketProduct product)
{
var ctx = ((IObjectContextAdapter)dbContext).ObjectContext;
ObjectStateManager objectStateManager = ctx.ObjectStateManager;
var l1 = objectStateManager.GetObjectStateEntries(EntityState.Added);
var l2 = objectStateManager.GetObjectStateEntries(EntityState.Modified);
var l3 = objectStateManager.GetObjectStateEntries(EntityState.Deleted);
//var l4 = objectStateManager.GetObjectStateEntries(EntityState.Detached);
var l5 = objectStateManager.GetObjectStateEntries(EntityState.Unchanged);
var existingProductInBasket = dbContext.BasketProducts.AsNoTracking().SingleOrDefault(b => b.BasketId == product.BasketId && b.ProductId == product.ProductId);
var l6 = objectStateManager.GetObjectStateEntries(EntityState.Added);
var l7 = objectStateManager.GetObjectStateEntries(EntityState.Modified);
var l8 = objectStateManager.GetObjectStateEntries(EntityState.Deleted);
//var l4 = objectStateManager.GetObjectStateEntries(EntityState.Detached);
var l9 = objectStateManager.GetObjectStateEntries(EntityState.Unchanged);
//objectStateManager.
dbContext.Entry<BasketProduct>(product).State = existingProductInBasket == null ? EntityState.Added : EntityState.Modified;
}
When you use asNoTracking() you get an unconnected entity that cannot be updated normally with EntityState.Modified. Then, one trick is to replace the cached entity values with non-cached entity values.
Here is the source code I use for special case where asNoTracking is necessary. It can be
private T ReplaceEntity(T cachedEntity, T nonCachedEntity) {
dbContext.Entry(cachedEntity).CurrentValues.SetValues(nonCachedEntity);
return cachedEntity;
}
A common use can be:
public virtual T FindFirstBy(System.Linq.Expressions.Expression<Func<T, bool>> predicate, bool asNoTracking = false)
{
if (asNoTracking)
{
T cachedEntity = dbContext.Set<T>().FirstOrDefault(predicate);
T nonCachedEntity = dbContext.Set<T>().AsNoTracking().FirstOrDefault(predicate);
return ReplaceEntity(cachedEntity, nonCachedEntity);
}
return dbContext.Set<T>().FirstOrDefault(predicate);
}
For your situation:
var cachedEntity = dbContext.BasketProducts.SingleOrDefault(b => b.BasketId == product.BasketId && b.ProductId == product.ProductId);
var nonCachedEntity = dbContext.BasketProducts.AsNoTracking().SingleOrDefault(b => b.BasketId == product.BasketId && b.ProductId == product.ProductId);
var product= ReplaceEntity(cachedEntity, nonCachedEntity);
dbContext.Entry<BasketProduct>(product).State = EntityState.Modified;
Hope it helps!!
That was actually by bad. It can be a bit difficult conceptually to get used to the idea of
how things get attached and tracked by EF. The secret is to remember that if you have an object
graph (objects with relationships to other objects) whenever an object of the graph gets attached with a state X then all the other objects in the graph seem to be attached as well in that state.
In my scenario i was quite stupidly using
var bpro = new BasketProduct(ba, ba.BasketProducts.First().Product, 3);
to create a test product that actually already existed in the database and it was part of the object
graph containing the basket and its products. When i tried to attach this "new" basket EF rightly complained that an object with the same key already exists in the attached graph!
Related
I have min 100 000 data into a Job_Details table and I'm using Entity Framework to map the data.
This is the code:
public GetJobsResponse GetImportJobs()
{
GetJobsResponse getJobResponse = new GetJobsResponse();
List<JobBO> lstJobs = new List<JobBO>();
using (NSEXIM_V2Entities dbContext = new NSEXIM_V2Entities())
{
var lstJob = dbContext.Job_Details.ToList();
foreach (var dbJob in lstJob.Where(ie => ie.IMP_EXP == "I" && ie.Job_No != null))
{
JobBO job = MapBEJobforSearchObj(dbJob);
lstJobs.Add(job);
}
}
getJobResponse.Jobs = lstJobs;
return getJobResponse;
}
I found to this line is taking about 2-3 min to execute
var lstJob = dbContext.Job_Details.ToList();
How can i solve this issue?
To outline the performance issues with your example: (see inline comments)
public GetJobsResponse GetImportJobs()
{
GetJobsResponse getJobResponse = new GetJobsResponse();
List<JobBO> lstJobs = new List<JobBO>();
using (NSEXIM_V2Entities dbContext = new NSEXIM_V2Entities())
{
// Loads *ALL* entities into memory. This effectively takes all fields for all rows across from the database to your app server. (Even though you don't want it all)
var lstJob = dbContext.Job_Details.ToList();
// Filters from the data in memory.
foreach (var dbJob in lstJob.Where(ie => ie.IMP_EXP == "I" && ie.Job_No != null))
{
// Maps the entity to a DTO and adds it to the return collection.
JobBO job = MapBEJobforSearchObj(dbJob);
lstJobs.Add(job);
}
}
// Returns the DTOs.
getJobResponse.Jobs = lstJobs;
return getJobResponse;
}
First: pass your WHERE clause to EF to pass to the DB server rather than loading all entities into memory..
public GetJobsResponse GetImportJobs()
{
GetJobsResponse getJobResponse = new GetJobsResponse();
using (NSEXIM_V2Entities dbContext = new NSEXIM_V2Entities())
{
// Will pass the where expression to be DB server to be executed. Note: No .ToList() yet to leave this as IQueryable.
var jobs = dbContext.Job_Details..Where(ie => ie.IMP_EXP == "I" && ie.Job_No != null));
Next, use SELECT to load your DTOs. Typically these won't contain as much data as the main entity, and so long as you're working with IQueryable you can load related data as needed. Again this will be sent to the DB Server so you cannot use functions like "MapBEJobForSearchObj" here because the DB server does not know this function. You can SELECT a simple DTO object, or an anonymous type to pass to a dynamic mapper.
var dtos = jobs.Select(ie => new JobBO
{
JobId = ie.JobId,
// ... populate remaining DTO fields here.
}).ToList();
getJobResponse.Jobs = dtos;
return getJobResponse;
}
Moving the .ToList() to the end will materialize the data into your JobBO DTOs/ViewModels, pulling just enough data from the server to populate the desired rows and with the desired fields.
In cases where you may have a large amount of data, you should also consider supporting server-side pagination where you pass a page # and page size, then utilize a .Skip() + .Take() to load a single page of entries at a time.
I am having an issue understanding why when adding a new entity to a DbSet of ObjectContext, that entity is not found will looking it up again.
using (var db = new SmartrailDB())
{
var cart01 = db.Carts.SingleOrDefault(x => x.Number == 0);
if (cart01 == null)
{
cart01 = new Cart { Number = 0 };
db.Carts.Add(cart01);
}
var cart02 = db.Carts.SingleOrDefault(x => x.Number == 0); // Should find the cart I just added - right?
Assert.IsNotNull(cart02); // Fails because cart02 does not exist in the db.Carts collection
}
Is anyone able to tell me what I am doing wrong here?
Also late on a Friday here so brain half asleep now.
You have to update your context before you try to access the entity. Just do:
db.SaveChanges(); right after db.Cart.Add(cart01);
If I load entity object and then assign one of properties to the same value as it had before, does framework detect changes or it would set IsModified flag to true anyway ?
This is how generated code for field Name looks like:
OnNameChanging(value);
ReportPropertyChanging("Name");
_Name = StructuralObject.SetValidValue(value);
ReportPropertyChanged("Name");
OnNameChanged();
I don't know which of those events set IsModified flag for that field and for the whole entity.
It looks like things are different now (EF6). I was researching this to see if I needed to use an if statement when setting property values to see if the "new value" is different. I tested with the following and the entity is not marked as modified:
var things = dbContext.Things.AsQueryable();
var thing = things.First();
string name = thing.Name;
thing.Name = name;
var entry = dbContext.Entry(thing);
var state = entry.State;
int count = dbContext.ChangeTracker.Entries().Count(e => e.State == EntityState.Modified);
var modified = entry.Property(x => x.Name).IsModified;
Your context only keeps track if your data got modified, not if it's different.
You can do a check like this:
private void CheckIfDifferent(DbEntityEntry entry)
{
if (entry.State != EntityState.Modified)
return;
if (entry.OriginalValues.PropertyNames.Any(propertyName => !entry.OriginalValues[propertyName].Equals(entry.CurrentValues[propertyName])))
return;
(this.dbContext as IObjectContextAdapter).ObjectContext.ObjectStateManager.GetObjectStateEntry(entry.Entity).ChangeState(EntityState.Unchanged);
}
source:https://stackoverflow.com/a/13515869/1339087
I am having a real issue with the EF v1. I have quite a big EDMX with maybe 50 entities mapped, but this one entity is causing me grief.
The entity has mappings to other entities which in effect are reference tables, but for some reason it is trying to do an insert and not just update itself.
Here is a fragment of my code:
using (var context = new someEntities()) {
var studentCourseJoin =
context.StudentCourseJoinSet.Where(o => o.Code == scjCode).First();
studentCourseJoin.EntryStatus = new EntryStatus { Code = viewModel.StudentDetails.EntryStatusCode };
studentCourseJoin.ParentalInHigherEducation = new ParentalInHigherEducation { Code = viewModel.StudentDetails.ParentalInHigherEducationCode };
studentCourseJoin.School = new School { Code = viewModel.StudentDetails.SchoolCode };
studentCourseJoin.Institution = new Institution { Code = viewModel.StudentDetails.InstitutionCode };
studentCourseJoin.LastSchoolEndYear = viewModel.StudentDetails.LastSchoolEndYear;
studentCourseJoin.LastInstitutionEndYear = viewModel.StudentDetails.LastInstitutionEndYear;
// Blows up here trying to do an insert on the studentCourseJoin.Institution.
// But if I removed this one, then it will blow up on another one.
context.SaveChanges(true);
}
If anyone has ANY ideas please, they would help a lot.
Try adding those lines before calling SaveChanges:
ObjectStateEntry entry = context.ObjectStateManager.GetObjectStateEntry(studentCourseJoin);
entry.ChangeState(EntityState.Modified);
Update:
Try this for Institution instead:
studentCourseJoin.Institution = context.Institutions.FirstOrDefault(i => i.Code == viewModel.StudentDetails.InstitutionCode);
I'm new to the entity framework and I'm really confused about how savechanges works. There's probably a lot of code in my example which could be improved, but here's the problem I'm having.
The user enters a bunch of picks. I make sure the user hasn't already entered those picks.
Then I add the picks to the database.
var db = new myModel()
var predictionArray = ticker.Substring(1).Split(','); // Get rid of the initial comma.
var user = Membership.GetUser();
var userId = Convert.ToInt32(user.ProviderUserKey);
// Get the member with all his predictions for today.
var memberQuery = (from member in db.Members
where member.user_id == userId
select new
{
member,
predictions = from p in member.Predictions
where p.start_date == null
select p
}).First();
// Load all the company ids.
foreach (var prediction in memberQuery.predictions)
{
prediction.CompanyReference.Load();
}
var picks = from prediction in predictionArray
let data = prediction.Split(':')
let companyTicker = data[0]
where !(from i in memberQuery.predictions
select i.Company.ticker).Contains(companyTicker)
select new Prediction
{
Member = memberQuery.member,
Company = db.Companies.Where(c => c.ticker == companyTicker).First(),
is_up = data[1] == "up", // This turns up and down into true and false.
};
// Save the records to the database.
// HERE'S THE PART I DON'T UNDERSTAND.
// This saves the records, even though I don't have db.AddToPredictions(pick)
foreach (var pick in picks)
{
db.SaveChanges();
}
// This does not save records when the db.SaveChanges outside of a loop of picks.
db.SaveChanges();
foreach (var pick in picks)
{
}
// This saves records, but it will insert all the picks exactly once no matter how many picks you have.
//The fact you're skipping a pick makes no difference in what gets inserted.
var counter = 1;
foreach (var pick in picks)
{
if (counter == 2)
{
db.SaveChanges();
}
counter++;
}
I've tested and the SaveChanges doesn't even have to be in the loop.
The below code works, too.
foreach (var pick in picks)
{
break;
}
db.SaveChanges()
There's obviously something going on with the context I don't understand. I'm guessing I've somehow loaded my new picks as pending changes, but even if that's true I don't understand I have to loop over them to save changes.
Can someone explain this to me?
Here's updated working code based on Craig's responses:
1) Remove the Type then loop over the results and populate new objects.
var picks = (from prediction in predictionArray
let data = prediction.Split(':')
let companyTicker = data[0]
where !(from i in memberQuery.predictions
select i.Company.ticker).Contains(companyTicker)
select new //NO TYPE HERE
{
Member = memberQuery.member,
Company = db.Companies.Where(c => c.ticker == companyTicker).First(),
is_up = data[1] == "up", // This turns up and down into true and false.
}).ToList();
foreach (var prediction in picks)
{
if (includePrediction)
{
var p = new Prediction{
Member = prediction.Member,
Company = prediction.Company,
is_up = prediction.is_up
};
db.AddToPredictions(p);
}
}
2) Or if I don't want the predictions to be saved, I can detach the predictions.
foreach (var prediction in picks) {
if (excludePrediction)
{
db.Detach(prediction)
}
}
The reason is here:
select new Prediction
{
Member = memberQuery.member,
These lines will (once the IEnumerable is iterated; LINQ is lazy) :
Instantiate a new Prediction
Associate that Prediction with an existing Member, *which is attached to db.
Associating an instance of an entity with an attached entity automatically adds that entity to the context of the associated, attached entity.
So as soon as you start iterating over predictionArray, the code above executes and you have a new entity in your context.