When deleting an entity, I get the following error message:
The operation failed: The relationship could not be changed because
one or more of the foreign-key properties is non-nullable. When a
change is made to a relationship, the related foreign-key property is
set to a null value. If the foreign-key does not support null values,
a new relationship must be defined, the foreign-key property must be
assigned another non-null value, or the unrelated object must be
deleted.
Fair enough. However, I have many many relationships and I don't know which one causes the error.
Is there a way to get the name of the relationship that causes the problem?
Is there a way to get the name of the relationship that causes the problem?
Unfortunately no without quite complex exploration of ObjectStateManager. This is quite annoying problem because the exception is too generic without any additional information. I think it is a nice request for improvement and with EF as and open source it should really be possible to improve the quality of the exception.
You will have to go through your modification code and check entities you are trying to delete. There will be some related dependent entity which is not deleted and hangs the deletion of the parent entity. Other approach recommended for EF is to use cascade deletes.
Related
I'm getting the following error when I SaveChanges after Removing an entity that has related entities containing data in the context as well. (The entity I'm deleting has the unique Primary Key). I have Cascading Delete configured at the SQL Server database level for the relation between the primary key table and the foreign key table.
"The operation failed: The relationship could not be changed because one or more of the foreign-key properties is non-nullable. When a change is made to a relationship, the related foreign-key property is set to a null value. If the foreign-key does not su...
The primary entity has its related data loaded explicitly prior to me removing the primary from the context. I assumed that EF and SQL Server would take care of the cascaded delete for me. If the related entity has no data the delete (of the primary entity) works fine. If there is data in the related entity, I get the error above.
Any suggestions?
The lesson is that EF has a learning curve. Keep exploring.
Anyway, I was "deleting" entities by setting the state to "Deleted" then calling SaveChanges. This seems to work fine if the entity has no related data. However, if you have an entity that has related "child" entities, you need to call Remove on the parent entity for the "delete" to cascade through the graph. Live and learn. I'm pretty sure this is the answer. I think for the time being I'm going to stop setting State for deletes and use Remove instead.
I have started using Entity Framework 4.1 with Code first. I really love this over the previous ado.net techniques.
I have a very simple situation in which there is a department table and an employee table in database. Each employee belongs to a department and a department has got many employees. The business rule is : While, deleting a department, if there are any associated employees, it should not allow deletion. I can write a small method just before deletion and check the dependancy. However, since my project is a much complex one with more than 300 db tables, I hate to do this. The relationships gets changed frequently which results in lot of changes in all the delete methods of the project.
In ado.net, in similar situations, I used to parse the exception thrown and get the name of the particular Foreign key constraint which was violated. Based on the name of the violated FK constraint, I used to give appropriate error message to client. This technique worked well even in a fairly large project with more than 150 tables.
How do I do a similar thing in EF ? How do I get which FK is violated when SaveChanges() is called ?
You need to get the Message of the inner most exception(usually its a SqlException). Then you can extract the FK name from that string and check which FK is violated.
I've been trying to find the answer to this question here. Several people seem to ask similar things, but I don't get the answers. I have an EF entity with a bunch of child entities (one-to-many relationship). I want to be able to delete the "parent" entity and have all the child entities deleted at the same time.
Some people mention "Cascade Delete" should be set on both EF model and database (Sql Server in my case). The problem is:
I have absolutely no idea how to do this (seems to be implied in those answers that you should know, but sorry...)
I have a feeling I've run into a similar problems before and found an answer somewhere that was simpler than setting this Cascade Delete. I may be wrong, maybe it is the only way, but if there is a simpler solution I'd like to know.
In either case, a clear example of how to get this working would be greatly appreciated!
In SQL Managment Studio go to your database and find the table where there should be a foreign key. Add a foreign key to the table pointing to the other table. I assume you know how to setup a foreign key. In the foreign key setup at the bottom of the dialog window you'll see a Delete property. Set it to Cascade. This will cause any dependent rows to be deleted whenever the parent row is deleted. Then go and update your data model in Visual Studio. Everything should be setup for you now.
Here is some relevant documentation on MSDN. Note though that there appears to be an error in the example. I received the following error from the EDMX designer when using this configuration.
Operations cannot be specified on ends with multiplicity '*'.
You should set the OnDelete property to Cascade for the end will be triggering deletes on the other end.
As an example, in a relationship involving customers and orders where you would like to have a customer's orders deleted along with the customer, you should set the OnDelete property for the Customer role to Cascade.
Note that only objects that have been loaded into the ObjectContext will be affected by a cascading delete. You will be relying on the cascading delete that you set in the database to look after any other records.
I use code first(entity framework). when i call DbContext.SaveChanges(), I get a primary key constraint because here is already such a record. I want to override the record if it already exists in the database. Which is the simplest way to do this. Checking each time I call savechanges for repeting primary keys is too hard in my project. Thanks
Unfortunately EF demands that you know if you are adding or modifing entity. So only ways are:
Keep this knowledge in your application and set proper EntityState in ObjectStateManager.
Load entity first. If exists modify its data, if doesn't create new entity and add it to context.
I have an issue with EF 4.0 that I hope someone can help with. I currently have an entity that I want to update in a last in wins fashion (i.e. ignore concurrency checks and just overwrite whats in the db with what is submitted). It seems Entity Framework not only includes the primary key of the entity in the where clause of the generated sql, but also any foreign key fields. This is annoying as it means that I don't get true last in wins semantics and need to know what value the fk field had before the update or I get a concurrency exception.
I am aware that this can be short circuited by including a foreign key field as well as the navigation property on the entity. I would like to avoid this if possible as it's not a very clean solution.
I was just wondering if there was any other way to override this behaviour? It seems like more of a bug than a feature. I have no problem with ef doing concurrency checks if I instruct it to do so but not being able to bypass concurrency completely is a bit of a hindrance as there are many valid scenarios where this is not needed
I am not 100% sure this will work, but I was curious myself and think I might have found a solution.
What if you set the [ConcurrencyCheck] attribute on a field that is immutable (in my case I used the ID (Primary Key). Since that will never be changed it will never trigger a concurrency exception and therefore clobber your entry.
Give it a whirl and see if that solves your issue.