Until EF core version used in .donet core 2.2, after the .Add command, EF fills the key column with a big negative number.
After 3.0 upgrade this does not happens anymore.
Here is the code:
var appointment = new Appointment
{
Date = DateTime.Today,
ProfessionalId = schedule.ProfessionalId
};
await service.AddAsync(appointment);
string message = null;
if (service.AddLastPrescription(appointment.Id, schedule.PacienteId))
....
The problem is that now the "appointment.Id" is zero and the call to the service function will fail (FK error).
This behavior was expected in 3.0?
update
AddAsync function
private DbSet<T> dbSet;
public async Task AddAsync(T t)
{
await dbSet.AddAsync(t);
}
where T is ModelBase:
public class ModelBase
{
[Key]
public int Id { get; set; }
public DateTime CreatedAt { get; set; }
public DateTime UpdatedAt { get; set; }
}
This behavior was expected in 3.0?
Yes, it is one of the 3.0 Breaking Changes - Temporary key values are no longer set onto entity instances.
The proposed solutions there are:
Not using store-generated keys.
Setting navigation properties to form relationships instead of setting foreign key values.
Obtain the actual temporary key values from the entity's tracking information. For example, context.Entry(blog).Property(e => e.Id).CurrentValue will return the temporary value even though blog.Id itself hasn't been set.
Option #1 doesn't make sense (apparently the affected places already use store generated keys).
Option #2 is preferable if you have navigation properties.
Option #3 is closer to the previous behavior, but requires access to the db context.
Related
Following through Julie Lerman's Pluralsight course EF Core 6 Fundamentals I've created two classes in my own project (my own design, but identical to the course in terms of class structure/data hierarchy):
Class 1: Events - To hold information about an event being held (e.g. a training course), with a title and description (some fields removed for brevity):
public class EventItem
{
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int EventItemId { get; set; }
[Required(AllowEmptyStrings = false)]
public string EventTitle { get; set; }
public string? EventDescription { get; set; }
[Required]
public List<EventCategory> EventCategories { get; set; } = new();
}
Class 2: Event categories - Each event can be linked to one or more pre-existing (seeded) categories (e.g. kids, adult).
public class EventCategory
{
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int EventCategoryId { get; set; }
[Required]
public string EventCategoryName { get; set; }
public List<EventItem>? EventItems { get; set; }
}
In my Razor form to create the event, the user can select from multiple categories. Using EF Core I take the posted data (via a VM/DTO object) and construct the relevant parent/child entities. However upon saving to the database I get an exception as EF Core tries to re-create the categories when they already exist:
Cannot insert explicit value for identity column in table
'EventCategories' when IDENTITY_INSERT is set to OFF.
My code explicitly looks up the existing categories selected by the user, but the context tracker appears to still believe they need inserting, in addition to creating the many-to-many relationship.
I'd appreciate any input as to why this is happening please:
using (var dbcontext = DbFactory.CreateDbContext())
{
// Get selected categories from user's check box list
var selectedCategoryIds = _eventCagetories.Where(c => c.isSelected).Select(c => c.EventCategoryId).ToList();
// Create new Event
var newEventItem = new EventFinderDomain.Models.EventItem() {
EventTitle = _eventItemDTO.EventTitle,
EventDescription = _eventItemDTO.EventDescription,
EventUrl = _eventItemDTO.EventUrl,
TicketUrl = _eventItemDTO.TicketUrl
};
// Find categories from the database based on their ID value
var selectedEventCategories = dbcontext.EventCategories.Where(c => selectedCategoryIds.Contains(c.EventCategoryId)).ToList();
// Add the categories to the event
newEventItem.EventCategories!.AddRange(selectedEventCategories);
// Add the event to the change tracker
await dbcontext.EventItems.AddAsync(newEventItem); // <-- Created correctly with child list objects added
// Detect changes for debugging
dbcontext.ChangeTracker.DetectChanges();
var debugView = dbcontext.ChangeTracker.DebugView; // <-- Incorrectly shows newEventItem.Categories being added
// Save to database
await dbcontext.SaveChangesAsync(); // <-- Cannot insert explicit value for identity column
}
The Event entity appears to be correctly created in the debugger with its related child categories included:
The change tracker however incorrectly shows the selected categories being added again when they already exist:
After commenting out every line of code in the app and adding back in until it broke, it emerges the problem was elsewhere within Program.cs:
builder.Services.AddDbContextFactory<EventFinderContext>(
opt => opt.UseSqlServer(new SqlConnectionStringBuilder() {/*...*/}.ConnectionString)
.EnableSensitiveDataLogging()
.UseQueryTrackingBehavior(QueryTrackingBehavior.NoTracking) // <-- THE CULPRIT
);
In the training video this method was described as a way of reducing overhead for disconnected apps. I had assumed that because of the disconnected nature of HTTP, this would be beneficial and that context would be re-established when creating the model's child data. This was incorrect on my part.
I should have used .AsNoTracking() only when retriving read-only data from my database. For example, loading in the child-data for a new model that wouldn't be modified directly, but used to create the many-to-many data (explicitly, for the category data option items only and not for the event data).
I have a problem creating a related entity in Entity Framework Core 2.0. I've just created the solution, consisting of an Asp.Net Core backend project, and a UWP project to act as client. Both solutions share model. The two models are:
public class UnitOfWork {
public int UnitOfWorkId { get; set; }
public string Name { get; set; }
public Human Human { get; set; }
}
public class Human {
public int HumanId { get; set; }
public string Name { get; set; }
public List<UnitOfWork> WorkDone { get; set; }
}
As you can see, model is very simple. One human has many units of work. By the way, the backend is connected to an Azure SQL database. I've seen the migration classes, and the database schema looks good to me.
The problem I have is when I want to create a unit of work referencing an existing human, using HTTP. The controller is fairly simple:
[HttpPost]
public UnitOfWork Post([FromBody] UnitOfWork unitOfWork) {
using (var db = new DatabaseContext()) {
db.UnitsOfWork.Add(unitOfWork);
var count = db.SaveChanges();
Console.WriteLine("{0} records saved to database", count);
}
return unitOfWork;
}
Again, nothing fancy here.
How can I create an unit of work, and assign it to an existing human? If I try it with an existing human, in this way
var humans = await Api.GetHumans();
var firstHuman = humans.First();
var unitOfWorkToCreate = new UnitOfWork() {
Name = TbInput.Text,
Human = firstHuman,
};
I get this error:
Cannot insert explicit value for identity column in table 'Humans' when IDENTITY_INSERT is set to OFF
I feel that setting IDENTITY_INSERT to ON will solve my problem, but this is not what I want to do. In the client, I'll select an existing human, write down a name for the unit of work, and create the latter. Is this the correct way to proceed?
EDIT: Following #Ivan Stoev answer, I've updated the UnitOfWork controller to attach unitofwork.Human. This led to
Newtonsoft.Json.JsonSerializationException: 'Unexpected end when deserializing array. Path 'human.workDone', line 1, position 86.'
Investigating - seen here - EFCore expects to create collections (like human.WorkDone) in the constructor, so I did it, and no more nulls deserializing. However, now I have a self-referencing loop:
Newtonsoft.Json.JsonSerializationException: Self referencing loop detected with type 'PlainWorkTracker.Models.UnitOfWork'. Path 'human.workDone'.
Any ideas? Thanks!
The operation in question is falling into Saving Disconnected Entities category.
Add methods marks all entities in the graph which are not currently tracked as new (Added) and then SaveChanges will try to insert them in the database.
You need a way to tell EF that unitOfWork.Human is an existing entity. The simplest way to achieve that is to Attach it (which will mark it as Unchanged, i.e. existing) to the context before calling Add:
db.Attach(unitOfWork.Human);
db.Add(unitOfWork);
// ...
Using Entity Framework 6.0, I am attempting to implement table splitting to improve query performance on tables with columns that contain BLOB data. I have followed the recommendations in this tutorial and it does indeed work as described.
Here's a very simplified example of the entity classes that map to one of my split tables ...
public class MyEntity
{
public string Id { get; set; }
public virtual MyEntityContent Content { get; set; }
public string Name { get; set; }
}
public class MyEntityContent
{
public string Id { get; set; }
public virtual MyEntity Entity { get; set; }
public byte[] Blob { get; set; }
}
... and the corresponding configuration code in the associated DbContext implementation ...
modelBuilder.Entity<MyEntity>().HasKey(e => e.Id).ToTable("MyEntities");
modelBuilder.Entity<MyEntityContent>().HasKey(c => c.Id).ToTable("MyEntities");
modelBuilder.Entity<MyEntity>().HasRequired(e => e.Content).WithRequiredPrincipal(d => d.Entity);
Given that the lazy-loaded Content property is Required by Entity Framework, it seems sensible to initialize it to a default value in the constructor of the containing MyEntity class ...
public MyEntity()
{
Content = new MyEntityContent();
}
... which enables a new instance of the class to be created and partially populated, without the risk of an exception being thrown by forgetting to initialize the required property value:
var entity = new MyEntity {Id = "XXX", Name = "something"};
I typically use a similar technique to initialize collection properties on EF entities and it works fine. However, in the above scenario, this initialization in the constructor has an unexpected effect: when retrieving existing entity instances from the database, the database value in the lazy-loaded property is ignored in favor of the empty default value.
This seems illogical to me. Doesn't Entity Framework create an entity object by first calling its default constructor and then applying its own property values to the created instance? If so, this should overwrite my default Content property value with a new instance of MyEntityContent, based on database data. This is how it seems to work with lazy-loaded collection properties.
If it's not possible to do this in the way I am expecting, is there an alternative technique for initializing lazy-loaded properties?
Don't initialize virtual members and perhaps, if you have to, handle any exceptions from uninitialized members.
I just had this issue with an entity with two virtual fields. Originally I had it initialize those two, but after removing them (and initializing the other fields to some default value), it started working for me. Try it out and let me know!
[Edit] I just realized I replied this to a slightly old post, didn't see the date. I guess I'll leave this answer here in case.
EF 4.1, POCO: I turned off AutoDetectChanges (Configuration.AutoDetectChangesEnabled = false) to speed up data update. Then I run Add or Attach with entity state changed to EntityState.Modified. All this causes references to other objects not being updated in database. However all scalar properties are updated successfully.
Profiler shown EF generates SQL update operation for every scalar property, but not for reference type, though I really changed its value in my code. This issue reproduced for every type of entity in my model.
Add operation or Attach with EntityState.Added both work fine. If I turn AutoDetectChanges back on, everything works fine as expected for updated records too.
Help me please to figure out what's wrong. I can not find any good comprehensive documentation on EF's Detect Changes.
UPDATE
I was asked to put some example of code to reproduce the issue. Domain:
public class Client
{
public int Id { get; set; }
public string Name { get; set; }
public virtual Address Address { get; set; }
}
public class Address
{
public int Id { get; set; }
public virtual string City { get; set; }
}
DataContext:
public class DataContext : DbContext
{
public DbSet<Client> Clients { get; set; }
public DbSet<Address> Address { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
modelBuilder.Entity<Client>().HasOptional(c => c.Address);
}
}
Add one record to Clint table and one to Address. Point Client to the Address. Then run the following code:
using (var cntx = new DataContext())
{
cntx.Configuration.AutoDetectChangesEnabled = false; // Reason of problem
var client = cntx.Clients.First();
client.Name = "Anna"; // This property will be updated
client.Address = null; // This property will not be updated
cntx.Clients.Attach(client);
cntx.Entry(client).State = EntityState.Modified;
cntx.SaveChanges();
}
This code does generates SQL script like this:
update [dbo].[Clients] set [Name] = 'Anna'
where ([Id] = 1)
Set AutoDetectChangesEnabled to true and run the code again, this time everything alright:
update [dbo].[Clients]
set [Name] = 'Anna', [Address_Id] = null
where (([Id] = 1) and [Address_Id]=1)
Note it does not matter if you change Address's value from specific value to null, or back to specific value, or one concrete value to other concrete value, any change is not tracked while AutoDetectChanges=false. Seems like EF bug.
See Change Tracking on MSDN
Well, I found out the way to set Reference property values that works even with AutoDetectChangesEnabled=false:
cntx.Entry(client).Reference(c => c.Address).CurrentValue = null;
However I definitely do not like it. 1) Code looks ugly; 2) You have to have access to context to make it work, which is not my case, I'd like this property being set outside of repository which only has access to DbContext. Is any other simpler way to let EF know the property value is changed?
Updated: Ok, I found simpler workaround: just run cntx.ChangeTracker.DetectChanges() before running cntx.SaveChanges(). It helps EF generate correct SQL update script
This question already has answers here:
EF code first: Cannot insert explicit value for identity column in table '' when IDENTITY_INSERT is set to OFF
(3 answers)
Closed 4 years ago.
I'm trying out Entity Framework 4's Code First (EF CodeFirst 0.8) and am running into a problem with a simple model that has a 1 <--> 0..1 relationship, between Person and Profile. Here's how they're defined:
public class Person
{
public int PersonId { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public DateTime? DOB { get; set; }
public virtual Profile Profile { get; set; }
}
public class Profile
{
public int ProfileId { get; set; }
public int PersonId { get; set; }
public string DisplayName { get; set; }
public virtual Person Person { get; set; }
}
The DB context looks like this:
public class BodyDB : DbContext
{
public DbSet<Person> People { get; set; }
}
I didn't define a DbSet for Profile because I consider People to be its aggregate root. When I try to add a new Person - even one without a Profile with this code:
public Person Add(Person newPerson)
{
Person person = _bodyBookEntities.People.Add(newPerson);
_bodyBookEntities.SaveChanges();
return person;
}
I get the following error:
Cannot insert explicit value for identity column in table 'People' when IDENTITY_INSERT is set to OFF.
The newPerson object has a 0 for the PersonId property when I call People.Add(). The database tables are People and Profiles. PersonId is the PK of People and is an auto-increment Identity. ProfileId is the PK of Profiles and is an auto-incement Identity. PersonId is a non-null int column of Profiles.
What am I doing wrong? I think I'm adhering to all the EF Code First's convention over configuration rules.
I get the following error:
Cannot insert explicit value for identity column in table 'People' when IDENTITY_INSERT is set to OFF.
I think that the IDENTITY_INSERT is the Auto Increment functionality which is off.
So, check the field PersonId in the database to see if it is an identity.
Besides, maybe this will fix your problem too.
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
public int PersonId { get; set; }
This will occur if you perform the following steps:
Create a non-identity PK field on a table.
Infer the Entity Model from that table.
Go back and set the PK identity to true.
The Entity Model and the database are out of sync. Refreshing the model will fix it. I had to do this just yesterday.
If you are using EF Code First, then, in addition to adding the [DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)] annotation attribute to the model.cs file as others have suggested here, you also need to make the same effective change on the modelMap.cs files (the fluent mapping instructions):
Change from:
this.Property(t => t.id)
.HasDatabaseGeneratedOption(DatabaseGeneratedOption.None);
to:
this.Property(t => t.id)
.HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
(I used the EF Power Tools to generate the entity models and the default mapping files, then later turned one Id column into a prmary key column and set it to IDENTITY in Sql Server, therefore, I had to update the attribute and the default mapping file.)
If you don't change it in both places, you'll still get the same error.
You situation reminds me situation I experience with EF Code First when PrimaryKey and ForeignKey are the same column.
There is no direct way to refresh the model, however the same effect can be achieved in 2 steps.
Comment out ProfileId in Profile class. Recompile and update database.
Uncomment Profile Id, add DatabaseGeneratedAttribute and update database again.
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.None), Key]
This way the generated ProfileId column becomes Key without Identity.
If you are using EF core and the fluent interface like me, I've found that the Scaffold-DbContext utility I've used to create the model from an existing db, generate a line for my column like that:
entity.Property(e => e.id).ValueGeneratedNever();
After I've changed the DB adding the IDENTITY attribute to my id, I had to change the row in:
entity.Property(e => e.id).ValueGeneratedOnAdd();
other than adding the [DatabaseGeneratedAttribute(DatabaseGeneratedOption.None), Key] decorator to the id field in my model class.
I'm not even sure if the latter is necessary. After resolved with the former fix, I didn't try to remove it.
I didn't have this problem until I added a composite key , so once I had 2 primary keys this occurred with EF 6.x.x
On my Key "Id" which has Identity Specification set to true I needed to add
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
Model properties now:
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
[Key, Column("Id", Order = 1)]
public int Id { get; set; }
[Key, Column("RanGuid", Order = 2)]
public string RanGuid { get; set; }
For the benefit of searchers: I got this error, but the above fixes did not work. It was due to an error on my part.
On my tables, I have a Guid Primary Key (non-clustered) and an int index.
The error was happening when trying to update the 'Post' with the 'Blog' info as a navigation property. See classes below:
public class Blog
{
public Guid BlogId { get; set; }
public int BlogIndex { get; set; }
// other stuff
}
public class Post
{
public Guid PostId { get; set; }
public int PostIndex { get; set; }
// other stuff
public Blog Blog { get; set; }
}
The issue was that when I was converting DTO's to models, the BlogId was being changed to a new Guid() (I made an error in the mapping). The resulting error was the same as detailed in this question.
To fix it, I needed to check the data was right when being inserted (it wasn't) and fix the incorrect change of data (in my case, the broken mapping).
Got this error in EF6, looked at the database and everything looked right with Identity Specification set to Yes. I then removed the different migrations and made one new migration from current models and then everything started working. Fastest solution since the application was not live yet and still in development.
Cannot insert explicit value for identity column in table
'Test' when IDENTITY_INSERT is set to OFF.
Here is the solution. Also see the attachment for more help.
Navigate to your EF model ".edmx" file >> Open it >> Now right click on the diagram and choose 'Update Model from Database'.
This will fix it because you made PK the Identity in your DB after you created your EF model.
help to recreate steps stated above
In my case it seems that EF doesn't like other type than INT identity field - mine was a BYTE (TINYINT on the SQL side).
Since I was able to update my project and change it to INT on the SQL, after re-running the Reverse Engineering Code First on VisualStudio, the error has immediately ceased to occur.
In my case it seems that EF doesn't like other type than INT identity field - mine was a BYTE (TINYINT on the SQL side).
I had this error too using PK of tinyint type. It's not that EF doesn't like it, it's seems that, unlike other cases, you have to specify that in your configuration like this:
this.Property(t => t.TableID).HasColumnName("TableID").HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);