I am using Entity Framework 4.3.1 and I am trying to insert a new record into the table my ProductVersion entity is based on.
The ProductVersion entity has 2 properties that make up a composite primary key for the table called ProductId and ProductOrdinal.
Whenever someone updates a product entry I am creating and passing a ProductVersion entity back to my repository, incrementing the ProductOrdinal property, and attempting to add the entity to the context and save it.
I keep getting the following error:
The property 'ProductOrdinal' is part of the object's key information and cannot be modified.
Neither of the columns that make up the key are autonumbering and I have annotated the properties in my POCO with the following:
[Key, Column("PROD_Ordinal", Order=2), DatabaseGenerated(DatabaseGeneratedOption.None)]
public long ProductOrdinal { get; set; }
Marc_S was exactly right in his comment as to why this was not working.
From the exception and your description it seems that you are incrementing the 'ProductOrdinal' property on the existing 'ProductVersion' instance and trying to save it. What you probably want to do is create a new instance of 'ProductVersion' from the existing instance and increment the 'ProductOrdinal' property and save the new instance.
Related
I'm using Entity Framework to handle data transactions and we have a user entity which had a primary key type integer named ID.
In our SQL Server the Identity specification was set to Yes, Is Identity also set to yes with an auto increment of 1.
To delete a user, I used this code:
ctx.Users.Attach(user);
ctx.Entry(user).State = EntityState.Deleted;
ctx.SaveChanges();
However, we have changed our user entity to have a Guid as a primary key:
public class User
{
DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
public Guid ID { get; set; }
public string Username { get; set; }
}
In the database, it is set to data type uniqueidentifier with a "Default Value or Binding" set to (newsequentialid())
After changing this, the Entity Framework code to delete a user throws the following error:
Attaching an entity of type 'Administration.Model.User' failed because another entity of the same type already has the same primary key value. This can happen when using the 'Attach' method or setting the state of an entity to 'Unchanged' or 'Modified' if any entities in the graph have conflicting key values. This may be because some entities are new and have not yet received database-generated key values. In this case use the 'Add' method or the 'Added' entity state to track the graph and then set the state of non-new entities to 'Unchanged' or 'Modified' as appropriate.
Why is it throwing this error? I suppose it has something to do with the way the primary key is generated, but how can I fix this?
Of course, I could use a linq query and use .Remove, but I want to keep the solution I had using an int value as primary key.
Given the Model:
Public Class Customer
Property Id() As Guid
Property FirstName() As String
Property MiddleName() As String
Property LastName() As String
Property Addresses() As ICollection(Of Address)
End Class
Public Class Address
Property Id() As Guid
Property Name() As String
Property Street() As String
Property City() As String
Property Zip() As String
Public Property Customer() As Customer
End Class
Entity Framework 6 Code First has created a column called Customer_Id in my table Addresses. Now, I'd like to add a Property Customer_Id to my class Address that represents the existing foreign key relation:
Public Class Address
Property Id() As Guid
Property Name() As String
Property Street() As String
Property City() As String
Property Zip() As String
Public Property Customer() As Customer
//Added
Public Property Customer_Id() As Guid
End Class
Unfortunately this results in an InvalidOperationException while creating the DbContext saying:
The model backing the 'DataContext' context has changed since the database was created.
I tried different property names (with and without underscore, different casing). But still no luck. So, what is the correct way to add those properties subsequently without the need for migrations? I assume it's possible, because the model does not really change, I am only changing from an implicit declaration of a property to an explicit...
Update:
The responses show me, that I did not explain the problem very well. After some more reading I found the correct names now: I have an application which is installed several times at customer locations (therefore dropping and recreating the database is no option). Currently, it depends on Entity Framework's Independent Associations, but I want to have the Foreign Key in my entity as well (this is no change to the model, the foreign key is already there, but does not exist as a property in my entity, since this is currently only relying on the IA instead). I did not manage to add it without EF thinking my Database is outdated.
for me two ways :
drop table __MigrationHistory : that is have the new model runs, but forget migration functionalities
create a new db by changing the connection string of the application. Replace old __MigrationHistory by __MigrationHistory of the newly created db
Never tested the second solution, but it should work.
Before using any solution:
backup you db.
Before using first solution: are you sure you will never need migration functionalities ?
This exception is because you change your model. You have to set migration strategy. Please look at:
http://msdn.microsoft.com/en-us/data/jj591621#enabling
(edited)
First of all you have to remove that exception. Even if you didn't add any new column to your database your model has changed because you added new property to Address class. If you check your DB you will find dbo.__MigrationHistory table with Model column. Last (earliest) value from that column is used for checking that your model and DB are compatible. I'm not sure but I think that EF stores there binary serialized model. So the solution is - recreate DB or add migration (probably empty migration).
(edited)
When you want to set FK you can do this very simple by Data Annotations
// c# example
public class Address
{
...
public string CustomerId { get; set; }
[ForeignKey("CustomerId")]
public Customer Customer { get; set; }
}
or in fluent api
// c# example
modelBuilder.Entity<Address>()
.HasRequired(arg => arg.Customer)
.WithMany()
.HasForeignKey(arg => arg.CustomerId);
or look at:
http://weblogs.asp.net/manavi/archive/2011/05/01/associations-in-ef-4-1-code-first-part-5-one-to-one-foreign-key-associations.aspx
http://msdn.microsoft.com/en-us/data/hh134698.aspx
I have a method for inserting in database.
I have 1:n relationship between the tables Point (n) and Line (1). Point has foreign key idLine.
However, the class Point in Entity Framework doesn't have the idLine property.
Now, in my method I have object of type Point, as parameter and here I have a problem because I don't know to what to assign the idSection of the new Point object which is inserted in the table.
How to add the idLine property in the Point class?
I'll assume you're using EF4.0, since this is not possible in previous version (EF1.0 does not include foreigh key properties in model).
In your generation wizard you need to make sure that "Include foreign key columns in the model" checkbox is checked when you're generating data model. Otherwise foreign key columns will be omitted when generating data.
If I'm remembering correctly you cannot simply add forign keys to classes that are already generated. You would need to manually edit all the mappings (not impossible, might be little bit troublesome if you are new to EF). Or you can simply remove this class from design area and add it again (making sure appropriate checkbox is checked this time). This might be simpler if you haven't customized generated classes.
add a foreign key in your model like following :-
public int? LineId { get; set; }
public virtual LineId LineId {get; set; } // this for one to one
I am using EF 4.1 with database first.
Example table:
CREATE TABLE dbo.Foo(
[ID] [int] IDENTITY(1,1) NOT NULL,
Created datetime not null default(getdate()),
Title varchar(80) not null
PRIMARY KEY CLUSTERED ([ID] ASC)
)
EF correctly loads the model with all 3 columns as nullable = false.
Output from code generation item "ADO.NET DbContext Generator":
public partial class Foo
{
public int ID { get; set; }
public System.DateTime Created { get; set; }
public string Title { get; set; }
}
In MVC3 I generate the FooController via the db context and foo model. When I bring up /Foo/Create and hit "Create" on the blank form it shows a validation error on "Created" field but not on "Title".
If I enter only a "created" date I get an exception:
Validation failed for one or more entities. See 'EntityValidationErrors'
property for more details
The exception is "The Title field is required".
I'm not sure why it works fine for one column but not the other. My first fix was to simply add the annotation, however the class code is auto generated by EF.
The only fix that seems to work is to use a partial metadata class: ASP.NET MVC3 - Data Annotations with EF Database First (ObjectConext, DbContext)
I can add the [Required] tag as desired however this should be unnecessary. Is this a bug in EF or am I just missing something?
This isn't a bug, EF simply doesn't add those attributes. As far as i know, the database-first approach (Entity classes generated by the designer) doesn't even perform the validation. The link you're refering to is a valid solution for your problem. The principle of buddy-classes which contain the actual metadata was introduced due to the fact, that you cannot add attributes to existing properties in a partial class.
The code-first approach has a built-in functionality to validate your annotations, see: Entity Framework 4.1 Validation. Another solution when using database-first would be to create a custom code-generator that applies those attributes T4 Templates and the Entity Framework.
I'm probably thinking about this all wrong but I have the following db tables:
When I run the EF Wizard in VS2008 I get the following model:
You'll notice that in the EF model shows that the Entity has no field for EntityTypeID or EntityStatusId. Instead it shows it as a navigation property, so the field appears to not be addressable when I instantiate an Entity (pardon the terminology confusion: Entity is a Table/Class in my name space not in the EF namespace). How can I assign an EntityTypeID and StatusTypeID when instantiating an Entity?
Yes, the entity framework hides foreign key ID properties and shows navigation properties instead. There is a lengthy discussion about why it does that, here. The usual means of assigning a reference to another entity is to assign the entity instance, rather than the foreign key ID value, like this:
var foo = new Entity();
var status = (from .... select ...).FirstOrDefault();
foo.StatusCodes = status;
However, it is possible to assign a foreign key ID directly, if you happen to know what it is:
foo.StatusCodesReference = new EntityKey(
"MyEntityContextName.StatusCodesEntitySetName", "StatusCodeId", value);
Obviously, substitute the real values in the above.