Is it possible in EF Code-First to update without querying the entire row in db by using stub objects,...
e.g.
public class Dinner
{
public int DinnerID { get; set; }
public string Title { get; set; }
public DateTime EventDate { get; set; }
public string Address { get; set; }
public string Country { get; set; }
public string HostedBy { get; set; }
}
Dinner dinner = dinner.DinnerID = 1;
dinner.HostedBy = "NameChanged"
nerdDinners.SaveChanges();
will the code above create an Update Statement which will make the following columns null for the row of DinnerID 1 ?
Title, EventDate, Address, Country
Is there a way or method like "PropertyModified" = true, then the rest make them = false, so that HostedBy is the only one that will be updated?
I think you are looking for ApplyCurrentValues
public void UpdateDinner(Dinner existingDinner)
{
var stub = new Dinner { DinnerId = existingDinner.DinnerId };
ctx.Dinners.Attach(stub);
ctx.ApplyCurrentValues(existingDinner);
ctx.SaveChanges();
}
ApplyCurrentValues copies the scalar values from the existing object to the object in the graph (in the above case - the stub entity).
From the Remarks section on MSDN:
Any values that differ from the original values of the object are marked as modified.
Is that what your after?
To build on Paul's answer, the following will work when you are using EF Model or Database First:
context.ObjectStateManager.GetObjectStateEntry(dinner).SetModifiedProperty("HostedBy");
I think you are looking for the Attach() method.
Attaching and Detaching Objects
Try this maybe, it is specific to EF Code First which seems to do it differently than just EF.
var dinner = context.Dinners.Find(1);
context.Entry(dinner).Property(d => d.HostedBy).IsModified = true;
context.SaveChanges();
From ADO.NET team blog
"Marking a property as modified forces an update to be send to the database for the property when SaveChanges is called even if the current value of the property is the same as its original value."
Related
I have a database first model.
My application UI provides a group of checkboxes, one for each value in Data_Type.
When the user checks one, I expect a row to be added in BUS_APPL_DATA_TYPE,
however I'm getting an error about Cannot insert explicit value for identity column in DATA_TYPE (And I absolutely do not actually want to insert data in this table)
My EF Model class for BUS_APPL has this property
public ICollection<BusApplDataType> BusApplDataType { get; set; }
And that EF Model class looks like
public partial class BusApplDataType
{
public int BusApplId { get; set; }
public int DataTypeId { get; set; }
[Newtonsoft.Json.JsonIgnore]
public BusAppl BusAppl { get; set; }
public DataType DataType { get; set; }
}
What exactly do I need to add to the BusApplDataType collection to get a record to be inserted in BUS_APPL_DATA_TYPE?
Edit:
At a breakpoint right before SaveChanges.
The item at index 2 is an existing one and causes no issues.
The item at index 3 is new. Without this everything updates fine. There is a DATA_TYPE with id 5 in the database.
The surrounding code, if it helps.
[HttpPut("{id}")]
public IActionResult Update(int id, [FromBody] BusAppl item)
{
...
var existing = _context.BusAppl.FirstOrDefault(t => t.Id == id);
...
existing.BusApplDataType = item.BusApplDataType; //A bunch of lines like this, only this one causes any issue.
...
_context.BusAppl.Update(existing);
_context.SaveChanges();
return new NoContentResult();
}
My issue was that I needed to use my context to look up the actual entity, using info passed, instead of using the one with all the same values that was passed into my api directly.
I'm trying to fetch (in disconnected way) an entity with its all related entities and then trying to update the entity. But I'm getting the following error:
Attaching an entity of type 'Feature' failed because another entity of the same type already has the same primary key value.
public class Person
{
public int PersonId { get; set; }
public string Personname { get; set }
public ICollection Addresses { get; set; }
}
public class Address
{
public int AddressId { get; set; }
public int PersonId { get; set; }
public string Line1 { get; set; }
public string City { get; set; }
public string State { get; set; }
public Person Person { get; set; }
public ICollection<Feature> Features { get; set; }
}
// Many to Many: Represented in database as AddressFeature (e.g Air Conditioning, Central Heating; User could select multiple features of a single address)
public class Feature
{
public int FeatureId { get; set; }
public string Featurename { get; set; }
public ICollection<Address> Addresses { get; set; } // Many-To-Many with Addresses
}
public Person GetCandidate(int id)
{
using (MyDbContext dbContext = new MyDbContext())
{
var person = dbContext.People.AsNoTracking().Where(x => x.PersonId == id);
person = person.Include(prop => prop.Addresses.Select(x => x.Country)).Include(prop => prop.Addresses.Select(x => x.Features));
return person.FirstOrDefault();
}
}
public void UpdateCandidate(Person newPerson)
{
Person existingPerson = GetPerson(person.Id); // Loading the existing candidate from database with ASNOTRACKING
dbContext.People.Attach(existingPerson); // This line is giving error
.....
.....
.....
}
Error:
Additional information: Attaching an entity of type 'Feature' failed because another entity of the same type already has the same primary key value.
It seems like (I may be wrong) GetCandidate is assigning every Feature within Person.Addresses a new instance. So, how could I modify the GetCandidate to make sure that the same instance (for same values) is bing assisgned to Person.Addresses --> Features.
Kindly suggest.
It seems like (I may be wrong) GetCandidate is assigning every Feature within Person.Addresses a new instance. So, how could I modify the GetCandidate to make sure that the same instance (for same values) is bing assisgned to Person.Addresses --> Features.
Since you are using a short lived DbContext for retrieving the data, all you need is to remove AsNoTracking(), thus allowing EF to use the context cache and consolidate the Feature entities. EF tracking serves different purposes. One is to allow consolidating the entity instances with the same PK which you are interested in this case, and the second is to detect the modifications in case you modify the entities and call SaveChanges(), which apparently you are not interested when using the context simply to retrieve the data. When you disable the tracking for a query, EF cannot use the cache, thus generates separate object instances.
What you really not want is to let EF create proxies which hold reference to the context used to obtain them and will cause issues when trying to attach to another context. I don't see virtual navigation properties in your models, so most likely EF will not create proxies, but in order to be absolutely sure, I would turn ProxyCreationEnabled off:
public Person GetCandidate(int id)
{
using (MyDbContext dbContext = new MyDbContext())
{
dbContext.Configuration.ProxyCreationEnabled = false;
var person = dbContext.People.Where(x => x.PersonId == id);
person = person.Include(prop => prop.Addresses.Select(x => x.Country)).Include(prop => prop.Addresses.Select(x => x.Features));
return person.FirstOrDefault();
}
}
I have a trouble with EF (6.1.3)
I have created next classes (with many-to-many relationship):
public class Record
{
[Key]
public int RecordId { get; set; }
[Required]
public string Text { get; set; }
public virtual ICollection<Tag> Tags { get; set; }
}
public class Tag
{
[Key]
public int TagId { get; set; }
[Required]
public string Name { get; set; }
public virtual ICollection<Record> Records{ get; set; }
}
And method:
void AddTags()
{
Record[] records;
Tag[] tags;
using (var context = new AppDbContext())
{
records = context.Records.ToArray();
}//remove line to fix
tags = Enumerable.Range(0, 5).Select(x => new Tag()
{
Name = string.Format("Tag_{0}", x),
Records= records.Skip(x * 5).Take(5).ToArray()
}).ToArray();
using (var context = new AppDbContext()){ //remove line to fix
context.Tags.AddRange(tags);
context.SaveChanges();
}
}
If I use two contexts, the records (which were added to created tags) will be duplicated. If I remove marked rows - problem disappears.
Is there any way to fix this problem without using the same context?
If you can, better reload entities or not detach them at all. Using multiple context instances in application is overall making things much more complicated.
The problem for you comes from the Entity Framework entity change tracker. When you load entitites from your DbContext and dispose that context, entities get detached from entity change tracker, and Entity Framework has no knowledge of any changes made to it.
After you reference detached entity by an attached entity, it (detached entity) immediately gets into entity change tracker, and it has no idea that this entity was loaded before. To give Entity Framework an idea that this detached entity comes from the database, you have to reattach it:
foreach (var record in records) {
dbContext.Entry(record).State = EntityState.Unchanged;
}
This way you will be able to use records to reference in other objects, but if you have any changes made to these records, then all these changes will go away. To make changes apply to database you have to change state to Added:
dbContext.Entry(record).State = EntityState.Modified;
Entity Framework uses your mappings to determine row in database to apply changes to, specifically using your Primary Key settings.
A couple examples:
public class Bird
{
[Key]
public int Id { get; set; }
public string Name { get; set; }
public string Color { get; set; }
}
public class Tree
{
[Key]
public int Id { get; set; }
public string Name { get; set; }
}
public class BirdOnATree
{
[Column(Order = 0), Key, ForeignKey("Bird")]
public int BirdId { get; set; }
public Bird Bird { get; set; }
[Column(Order = 1), Key, ForeignKey("Tree")]
public int TreeId { get; set; }
public Tree Tree { get; set; }
public DateTime SittingSessionStartedAt { get; set; }
}
Here's a small entity structure so that you could see how it works. You can see that Bird and Tree have simple Key - Id. BirdOnATree is a many-to-many table for Bird-Tree pair with additional column SittingSessionStartedAt.
Here's the code for multiple contexts:
Bird bird;
using (var context = new TestDbContext())
{
bird = context.Birds.First();
}
using (var context = new TestDbContext())
{
var tree = context.Trees.First();
var newBirdOnAtree = context.BirdsOnTrees.Create();
newBirdOnAtree.Bird = bird;
newBirdOnAtree.Tree = tree;
newBirdOnAtree.SittingSessionStartedAt = DateTime.UtcNow;
context.BirdsOnTrees.Add(newBirdOnAtree);
context.SaveChanges();
}
In this case, bird was detached from the DB and not attached again. Entity Framework will account this entity as a new entity, which never existed in DB, even though Id property is set to point to existing row to database. To change this you just add this line to second DbContext right in the beginning:
context.Entry(bird).State = EntityState.Unchanged;
If this code is executed, it will not create new Bird entity in DB, but use existing instead.
Second example: instead of getting bird from the database, we create it by ourselves:
bird = new Bird
{
Id = 1,
Name = "Nightingale",
Color = "Gray"
}; // these data are different in DB
When executed, this code will also not create another bird entity, will make a reference to bird with Id = 1 in BirdOnATree table, and will not update bird entity with Id = 1. In fact you can put any data here, just use correct Id.
If we change our code here to make this detached entity update existing row in DB:
context.Entry(bird).State = EntityState.Modified;
This way, correct data will be inserted to table BirdOnATree, but also row with Id = 1 will be updated in table Bird to fit the data you provided in the application.
You can check this article about object state tracking:
https://msdn.microsoft.com/en-US/library/dd456848(v=vs.100).aspx
Overall, if you can avoid this, don't use object state tracking and related code. It might come to unwanted changes that are hard to find source for - fields are updated for entity when you don't expect them to, or are not updated when you expect it.
I am writing an API using WebAPI 2.0 and EF6.0 using code first.
So its necessarily a disconnected dbcontext scenario.
My domain is as as below
public class Patient
{
public int Id { get; set; }
public string Name { get; set; }
public string Email ( get; set; }
public virtual Nutritionist Nutritionist { get; set; }
}
public class Nutritionist
{
public int Id { get; set; }
public string Name { get; set; }
public virtual List<Patient> Patients { get; set; }
}
The UI will allow Patient to select a different Nutritionist if she is not happy with current one. So my API needs to support this. I presumed this would be a simple update on the Patient. But following unit test fails.
[TestMethod]
public void Changing_Nutritionist_In_Disconnected_Context_Works()
{
Patient p;
Nutritionist n;
using (var c = new Context())
{
// Get a patient where I know p.Nutritionist.Id == 1 in database.
p = c.Patients.Find(1);
// Get some other nutritionist
n = c.Nutritionists.Find(3);
}
using (var c = new Context())
{
//change patient's email and nutritionist
p.Email = "patient#domain.com";
p.Nutritionist = n;
c.Patients.Attach(p);
c.Entry(p).State = EntityState.Modified;
c.SaveChanges();
}
using (var c = new Context())
{
Assert.AreEqual(3,c.Patients.Find(1).Nutritionist.Id);
}
}
I expected that SaveChanges() would save changes to both properties of the patient p.Email and p.Nutritionist. But in database, only the email is changed and Nutritionist_Id field continues to show old value. So for some reason, dbContext is ignoring changes to navigation property p.Nutritionist
The SQL profiler shows following UPDATE query fired by EF
exec sp_executesql N'UPDATE [dbo].[Patients]
SET [Name] = #0, [Email] = #1
WHERE ([Id] = #2)
',N'#0 nvarchar(max) ,#1 nvarchar(max) ,#2 int',#0=N'some name',#1=N'patient#domain.com',#2=1
go
Wonder what i could be missing out on.
Yes I could use an explicit property p.NutritionistId but I was just trying to be a purist :)
I found out that following code works...
cn.Patients.Attach(p);
cn.Nutritionists.Attach(n);
cn.Entry(p).Reference(x => x.Nutritionist).Load();
p.Nutritionist = n;
cn.Entry(p).State = EntityState.Modified;
cn.SaveChanges();
It seems that EF does not automatically attach the related entries... p.Nutritionist in this case.
Also as Gert Arnold mentioned in the comment above, nor does it load it.
So explicitly loading the p.Nutritionist and then changing its value with and attached entity makes EF happy.
I am still wondering why EF would not do all this on its own as it seems a logical programming intent that when I attach a new entity and mark it as EntityState.Modified, I want to save the whole of it rather than just scalar properties.
I am using EF Code First 5.
I have 3 entities/POCO classes - Proposal, Document and Template that are related.
Proposal has a M to M relationship with Document table.
Template has a M to M relationship with Document table.
Here are my POCO C# classes
public class Document {
public int Id { get; set; }
public string FileName { get; set; }
public ICollection<Proposal> Proposals { get; set; }
public ICollection<Template> Templates { get; set; }
}
public class Proposal {
public int Id { get; set; }
public string Title{ get; set; }
public string Description { get; set; }
public ICollection<Document> Documents { get; set; }
}
public class Template {
public int Id { get; set; }
public string Title{ get; set; }
public string Description { get; set; }
public ICollection<Document> Documents { get; set; }
}
In my front end MVC app the user creates a proposal and adds documents to it.
I then receive the posted data in my MVC action method and add all the document to the proposal Documents collection
proposal.Description = model.Description;
proposal.Documents = GetDocumentsFromPostedFiles(model.Files);
db.Entry(proposal).State = EntityState.Added;
db.SaveChanges();
This work perfectly as the documents get assigned unique ids when saving to the db and are linked to my proposal.
However in the same screen with the same action the user has the option to save the documents he adds to the proposal to a new template.
So I want the Template table to get the reference the same documents that is being added to the Proposal in my one MVC action method.
I receive the posted data
- the 1 Proposal.
- Many Documents
- the new Template Title, Description
so what I want to update is all 3 tables with this posted data.
I tried the following:
proposal.Description = model.Description;
proposal.Documents = GetDocumentsFromPostedFiles(model.Files);
template.Description = model.TemplateDescription;
template.Documents = proposal.Documents();
db.Entry(proposal).State = EntityState.Added;
db.Entry(template).State = EntityState.Added;
db.SaveChanges();
This obviously updates incorrectly since the new unadded Documents have a Document id not set (value is default of 0) since the database will set it in the database after the db.SaveChanges so when I run it the templates' document ids' are incorrectly saved as 0.
How do I tell Entity Framework the template object's documents are related to the just added proposal documents?
I use the starting point of the 1 to M of either proposal or template to tell entity framework to add them to the database but as in my case since I have two 1 to M relationships how do I tell EF that the two M tables are in fact the same table when I do my initial db.SaveChanges?
Any other possible solution for this? I can only think of saving the proposal to the database first and reading all the just added documents with their primary key created ids from the database and then adding them to my Template.
This would result in a db.SaveChanges , Linq db Fetch and db.SaveChanges again where I would rather want to do this in one db.SaveChanges.
Call SaveChanges() after the proposal initialization:
proposal.Description = model.Description;
proposal.Documents = GetDocumentsFromPostedFiles(model.Files);
db.Entry(proposal).State = EntityState.Added;
db.SaveChanges();
template.Description = model.TemplateDescription;
template.Documents = proposal.Documents;
db.Entry(template).State = EntityState.Added;
db.SaveChanges();