In Entity Framework 6, when a Model has a [Key] field defined, is it possible to set this value manually, or will the DbContext always set this value itself?
I have done some research, and I cannot quickly find this answer. First I thought that this is possible, tried to set the id in a Create ActionResult, and the id was still added as an increment on the last added DbSet object.
Hence this question.
Thanks
Related
I am trying to insert multiple rows using the following code. SaveChanges() works for the first record but if fails when it tries the next one. My guess is that each time it is trying to insert all records. Not sure if this is correct or not, and if it is correct how can I change the code to make it correct. Following is my code:
Contrroller:
foreach(var m in pms)
{
_pmService.AddPms(m);
}
And in _pmService.AddPms:
_pmRepository.Add(pm);
_pmRepository.SaveChanges();
_pmRepository.Add (actually this is from BaseRepository and pmRepository extends this Base)
_ctx.Set<T>().Add(entity);
Finally, here is my SaveChanges() (again this is also from BaseRepostiroy)
_ctx.ChangeTracker.DetectChanges();
return _ctx.SaveChanges();
So in controller, I am looping through each entry, and then calling Add. The Add in service is calls Add in BaseRepository and then it does the SaveChanges(). For first record it works without any issues but 2nd record onwards it fails. And following is the error:
"Saving or accepting changes failed because more than one entity of type XXXXXXXXXXXXX have the same primary key value. Ensure that explicitly set primary key values are unique. Ensure that database-generated primary keys are configured correctly in the database and in the Entity Framework model. Use the Entity Designer for Database First/Model First configuration. Use the 'HasDatabaseGeneratedOption\" fluent API or 'DatabaseGeneratedAttribute' for Code First configuration."
And I am using DatabaseFirst approach.
I found the answer it is with StoreGeneratedPattern. I had to set this Identity in edmx file for the primary key field and it worked.
StoreGeneratedPattern="Identity"
This happens in ASP.NET MVC 2, .NET 4 (EF 4). My Address entity has a reference to the Post reference. Zip is the primary key of the Post entity. Another property in Post entity is CityName. In my views I allow users to change the CityName for the address which automatically (via jquery) loads up the corresponding Zip and stores it inside a hidden field.
When posted, both values are posted fine and binded to the Address's Post reference. But UpdateModel() fails to update them. It says that the Zip is part of the entity's Entity Key and cannot be changed.
I would gladly load up the Post entity by the new Zip and manually assign it to the existing Address but for all other properties I stall want to rely on UpdateModel().
How can I achieve that? One would think that in EF4 stuff like this has been resolved..
By default the entity framework generated classes put restrictions on changing primary key values. This is good. You shouldn't change a PK for any reason at all. Changing PKs outside of add scenarios has pretty huge ramifications for state tracking and the general health of your system.
To solve this problem you want to tell UpdateModel not to update your primary keys using the exclude parameter.
I have a Client entity and PostCode entity in Linq to SQL model. The Clients table in database contains client_postcode column which is a FK column to postalcode column in PostCode table, which is a varchar column primary key for PostCode table.
When updating Client, in my code I do this
// postcode
updating.PostCode = (from p in ctx.PostCodes
where p.postalcode.Equals(client.PostCode.postalcode)
select p).First();
where client object is provided from ASP.NET MVC View form. This code seems to set the PostCode related entity fine. But when calling SubmitChanges() I receive the following exception:
Value of member 'postalcode' of an object of type 'PostCode' changed. A member defining the identity of the object cannot be changed. Consider adding a new object with new identity and deleting the existing one instead.
So I am currently unable to change the related entity. How is that done in Linq to Sql?
UPDATE:
After further review and troubleshooting I found out that the problem is in ASP.NET MVC UpdateModel() call. If I call UpdateModel() to update the existing entity with the edited data, something is wrong with the FK assignement for PostCode. If I don't call UpdateModel and do it by hand, it works.
Any ideas what goes wrong in UpdateModel() that it can't set the relationship to foreign key entities correctly?
I am updating this question and starting a bounty. The question is simplified. How to successfully use L2S and UpdateModel() to work when updating items (with related entities as FK) in ASP.NET MVC Edit views?
It seems to me that you are receiving PostCode.postalcode in the http post request.
Based on how model binding works, the UpdateModel call updates .PostCode.postalcode of the model you are passing to it.
Use this overload to include or exclude specific properties.
Wouldn't updating.client_postcode = client.client_postcode; accomplish what you want?
Client.PostCode should be looked up on seek based on client_postocde.
You can not do what you are trying, you cannot change the Postcode like that.
James' idea is in the right direction.
Updatemodel() takes the matching values from the Formcollection
How do these values come in the Formcollection? What are their keys?
basically there are 2 ways in editing an object.
option 1:
all the value names you want to update have corresponding keys in the Formcollection, which leaves you just to call UpdateModel() of the original object. do SubmitChanges()
option 2:
Get the original object, change it's values manually (because the keys dont correspond) and do SubmitChanges()
you are tying to change a link, you cant do that. you can only edit the updating.client_postcode which in this case is a string?
Can you please copy the whole action here? So I can write some code for you without gambling.
My current setup:
I have an entity object with some properties, among them an int Id. To communicate with the database, I've created a repository with, among others, the following method:
public int Add(TEntity entity)
{
ObjectSet.AddObject(entity);
return entity.Id;
}
(It's a generic repository, that requires that TEntity is a class, and that it implements IEntity, which is just an interface with an int Id property.)
My problem:
Now, when I want to create a new entity for adding to the repository, I need to give it an id. However, that doesn't allow EF to automatically generate the id for me, since it will already have a value.
Possible solutions:
I have only been able to think of these two possibilities.
Make the Id property nullable
Pass an EntryInputModel to the repository instead, and then do the mapping there.
Currently I'm binding to EntryInputModel in my Controller, and mapping it to an Entry using AutoMapper. If I need to change this, I also need to re-think the dependencies in my project, since the ...InputModel and ...ViewModel classes are currently only available to my Web application.
Which is preferable? Are there more ways to counter this?
If you're using SQL Server as the backend, my recommended solution would be to make the ID column an INT IDENTITY on the database, and a not-nullable column in your entity object.
When adding a new entity, assign the ID some arbitrary value, like -1 or something, or no value at all, even. The actual ID will be generated automatically by SQL Server when you insert the new entity (
EntityContext.AddToEntities(newEntity);
EntityContext.SaveChanges();
and it will be automagically be signalled back to EF so you'll be able to use it right away once it's inserted:
int newEntityID = newEntity.ID;
Works like a charm - at least in my test apps :-)
you can have generated unique id's that are not generated by the datastore/EF, allowing you to define them before passing the object into EF... (think of Guid's)
PLEASE NOTE: I've answered my own question with a link to an answer to a similar question. I'll accept that answer once I'm allowed to (unless anyone comes up with a better answer meantime).
I have a database column defined as NVARCHAR(1000) NOT NULL DEFAULT(N'') - in other words, a non-nullable text column with a default value of blank.
I have a model class generated by the Linq-to-SQL Classes designer, which correctly identifies the property as not nullable.
I have a TextAreaFor in my view for that property. I'm using UpdateModel in my controller to fetch the value from the form and populate the model object.
If I view the web page and leave the text area blank, UpdateModel insists on setting the property to NULL instead of empty string. (Even if I set the value to blank in code prior to calling UpdateModel, it still overwrites that with NULL). Which, of course, causes the subsequent database update to fail.
I could check all such properties for NULL after calling UpdateModel, but that seems ridiculous - surely there must be a better way?
Please don't tell me I need a custom model binder for such a simple scenario...!
Might be duplicate or something in the line of this:
MVC binding form data problem
I fear custom model binder will be necessary. ;)
You might want to use a partial class implementation of your entity that implements the on property changed handler for that particular property. When you detect that the property has been changed to NULL, simply change it to string.Empty. That way anytime NULL is assigned to the property it gets reset to the empty string.