I have an Entity. Mandate. Every mandate has a required:many relation to a Person (NavigationProperty). I use the DbContext API with (LazyLoadingEnabled, AutoDetectChangesEnabled, ValidateOnSaveEnabled, ProxyCreationEnabled)
Now I like to delete a Mandate entity. The mandate entities are loaded by another context with AsNoTracking().
message.Result.
ObserveOn(On<DataComposition>.Scheduler).
Where(r => r).
Subscribe(_ =>
{
using (var unit = UnitOfWork.Begin())
{
var mandate = this.SelectedItem.OriginalEntity;
this.mandateRepository.Attach(mandate);
// mandate.Person.ToString();
this.mandateRepository.Delete(mandate);
unit.Commit();
}
this.List.RemoveOnUi(this.SelectedItem);
});
Now during committing I get the following exception: Entities in 'CodeFirstContainer.Mandates' participate in the 'Mandate_Person' relationship. 0 related 'Mandate_Person_Target' were found. 1 'Mandate_Person_Target' is expected.
The delete works if I include the Person Property during the population/selection or if I visit the Property (lazyloading), but I DONT LIKE to materialize/hold many entities only for the deletion case and I DONT LIKE to trigger more than a single DELETE query to db!
The fact that, if you have the navigation property mandate.Person populated, the following SQL statement ...
delete [dbo].[Mandates]
where (([Id] = #0) and ([PersonId] = #1))
... is sent to the database, lets me think that the navigation property indeed must be populated with a person with the correct PersonId to delete the parent.
I have no idea why Entity Framework just doesn't send a delete statement with the primary key ...
delete [dbo].[Mandates]
where ([Id] = #0)
... as I had expected.
Edit
If the Mandate entity has a foreign key property PersonId for the Person navigation property, the expected SQL (the second above) is sent to the database. In this case the Person navigation property can be null and the value of the FK property PersonId doesn't matter.
Edit 2
If you don't want to introduce a FK property the way with the least DB-roundtrip-costs would probably be to fetch the person's Id and then create a dummy person with that key in memory:
// ...
var personId = context.Mandates
.Where(m => m.Id == mandate.Id)
.Select(m => m.Person.Id)
.Single();
mandate.Person = new Person { Id = personId };
this.mandateRepository.Attach(mandate);
this.mandateRepository.Delete(mandate);
// ...
Related
Apparently, EF6 doesn't like objects that have multiple foreign key properties that use the same key value, but do not share the same reference. For example:
var user1 = new AppUser { Id = 1 };
var user2 = new AppUser { Id = 1 };
var address = new Address
{
CreatedBy = user1, //different reference
ModifiedBy = user2 //different reference
};
When I attempt to insert this record, EF throws this exception:
Saving or accepting changes failed because more than one entity of type
'AppUser' have the same primary key value. [blah blah blah]
I've discovered that doing this resolves the issue:
var user1 = new AppUser { Id = 1 };
var user2 = user1; //same reference
I could write some helper code to normalize the references, but I'd rather EF just know they're the same object based on the ID alone.
As for why EF does this, one explanation could be that its trying to avoid doing multipe CRUD operations on the same object since separate instances of the same entity could contain different data. I'd like to be able to tell EF not to worry about that.
Update
So it's as I suspected per my last paragraph above. In absense of a means to tell EF not to do CRUD on either instance, I will just do this for now:
if (address.ModifiedBy.Id == address.CreatedBy.Id)
{
address.ModifiedBy = address.CreatedBy;
}
Works well enough so long as I am not trying to do CRUD on either.
Update2
I've previously resorted to doing this to prevent EF from validating otherwise-required null properties when all I need is the child entity's ID. However, it doesn't keep EF from going into a tizzy over separate instances with the same ID. If it's not going to do CRUD on either AppUser object, why does it care if the instances are different?
foreach (var o in new object[] { address.ModifiedBy, address.CreatedBy })
{
db.Entry(o).State = EntityState.Unchanged;
}
If you get AppUser from context, then you will not need to do anything, because Entity Framework will track entities:
var user1 = context.AppUsers.Find(1);
var user2 = context.AppUsers.Find(1);
var address = new Address
{
CreatedBy = user1, //different reference
ModifiedBy = user2 //different reference
};
Now, they both will point to same objects and will not cause to conflict.
You can add two extra properties to have the Id for the main objects which is the AppUser, then you can use only one AppUser object and reference it for both the created and modified by properties.
CreatedById = user1.Id,
ModifiedById = user1.Id
Otherwise, your code will end up by saving two instances of AppUser with the same primary key.
Another approach is to set both the foreign key properties to only one AppUserobject
The explanation is that EF's change tracker is an identity map. I.e. a record in the database is mapped to one, and only one, CLR object.
This can be demonstrated easily by trying to attach two objects with the same key:
context.AppUsers.Attach(new AppUser { Id = 1 });
context.AppUsers.Attach(new AppUser { Id = 1 });
The second line will throw an exception:
Attaching an entity of type 'AppUser' failed because another entity of the same type already has the same primary key value.
This also happens if you assign
CreatedBy = user1, //different reference
ModifiedBy = user2 //different reference
Somewhere in the process, user1 and user2 must be attached to the context, giving rise to the exception you get.
Apparently, you have a function that receives two Id values that can be different or identical. Admittedly, it would be very convenient if you could simply create two AppUser instances from these Ids, not having to worry about identical keys. Unfortunately, your solution ...
if (address.ModifiedBy.Id == address.CreatedBy.Id)
... is necessary. Solid enough, though.
Suppose the following tables
ParentEntities
ParentID
ChildEntities
ChildID
ParentID
These tables do not have a FK defined in the schema.
In EF designer, after generating from DB, I add an association:
- Parent Multiplicity: 1
- Child Multiplicity: 0 or 1
When I build, I get the error: "Error 3027: No mapping specified for the following EntitySet/AssociationSet - ParentChild"
But if I try to configure table mapping for the association like this..
Maps to ChildEntities
Parent
ParentID <-> ParentID (parent entity prop <-> child table column)
Child
ChildID <-> ChildID (child entity prop <-> child table column)
.. I get this: Error 3007: Problem in mapping fragments starting at lines xxx, xxx: Column(s) [ParentID] are being mapped in both fragments to different conceptual side properties.
Why this is an error doesn't make sense. Limitation of the current implementation?
[EDIT 1]
I'm able to make this work by creating a 1-N association. That's not ideal, but it works just the same, just have to add a read-only child property in a partial:
public partial class Parent
{
public Child Child { get { return Childs.Any() ? null : Childs.First(); } }
}
This seems like the best solution for me. I had to add a FK to the database to get EF to generate the association and navigation property, but once it was added I was able to remove the FK, and further updates to the model from the DB did not remove the association or Navigation properties.
[EDIT 2]
As I was investigating how to work around not caring about the association being modeled in EF, I ran into another issue. Instead of the read-only Child property I made it normal ..
public partial class Parent
{
public Child Child { get; set; }
}
.. but now I need a way to materialize that from the query:
var query = from parents in context.Parents
// pointless join given select
join child in context.Childs
on parents.ParentID equals child.ParentID
select parents;
I can select an anonymous type ..
// step 1
var query = from parents in context.Parents
join child in context.Childs
on parents.ParentID equals child.ParentID
select new { Parent = parents, Child = child };
.. but then I've got to consume more cycles getting that into my entity:
// step 2
var results = query.Select(x => {
var parent = x.Parent;
parent.Child = x.Child;
return parent; });
Is there a better/streamlined way to do this from the query select so the EF materializer can do it from the get-go? If not, then I'll resort to Edit 1 methodology ..
Ef Code first requires 1->0..1 relationships for the Child to have the same primary key.
Maybe this a similar restriction In the modeler in this circumstance.
ParentId (Key) required in Both tables.
I have never tried adding such relationships in designer afterwords in DB first.
EDIT: to match your EDIT2:
I would stay on the direction . Use Navigation properties to get from Join back to original class A and B.
query = context.Set<JoinTable>.Where(Jt=>Jt.NavA.Id == ClassAId
&& Jt.navB.Id == ClassBId)
use a select if your need entries returned from either ClassA or ClassB.
I have a problem, I have a wizard that can update data AND insert data. So, if I have an existing list of team members, I can update their roles but If necessary, I can also add/insert a person to this team. So I can update roles and insert a new team member into the same table all during the same transaction. Data can be updated to and inserted to table teamMembers.
When I try to add a new teamMember, I also have an existing member where I simply want to update his role.
Both changes happen to the same table called TeamMember. When I debug the context, everything looks good. it shows that there are two changes that will occur for the TeamMember table. One transaction is the update and the other transaction is the insert. When I perform an update using:
var teamMember = new TeamMember
{
Name = user.FullName,
UserProfileId = user.UserProfileId,
RoleId = user.RoleId
};
TeamMemberList.Add(teamMember);
project.TeamMembers = TeamMemberList;
//And then call
this.Context.Projects.Attach(project);
this.Context.Entry(project).State = System.Data.EntityState.Modified;
it updates but the record that needs to be inserted fails.
HOW CAN I DO BOTH AN INSERT AND UPDATE TO THE SAME TABLE DURING THE SAME TRANSACTION?
CURRENT ERROR IS:
The changes to the database were committed successfully, but an error occurred while updating the object context. The ObjectContext might be in an inconsistent state. Inner exception message: A referential integrity constraint violation occurred: The property values that define the referential constraints are not consistent between principal and dependent objects in the relationship.
I think you need to add the TeamMember entity to the context's global list. Something like:
var teamMember = new TeamMember()
{
Name = user.FullName,
UserProfileId = user.UserProfileId,
RoleId = user.RoleId
}
project.TeamMembers.Add( teamMember );
this.Context.TeamMembers.Add( teamMember );
this.Context.SaveChanges();
How about loading the existing project entity first and then adding members.
var project = this.Context.Project.Where(p => p.ID = "bar").Include("TeamMembers").FirstOrDefault();
var teamMember= new TeamMember
{
Name = user.FullName,
UserProfileId = user.UserProfileId,
RoleId = user.RoleId
};
project.TeamMembers.Add(teamMember);
this.Context.SaveChanges()
Let's say I have a Person class and an Order class, with foreign keys in the DB. The EF model will mark Person with a List of Orders and Order with a Person instance.
If I want to set the Person for the Order, do I really have to do it with an instance of Person?
Is there not a slimmed down way to do so, say with just a PersonID ?
To assign Person entity to a Order without loading Person entity, you have to do something like this:
var db = new OneToManyEntities();
var Order = new Order { OrderId = 100, OrderName = "Order name" };
Order. PersonReference.EntityKey = new EntityKey("OneToManyEntities.Person ","PersonID",10);
db.AddToOrders(Order);
db.SaveChanges();
Puzzled's answer is correct for EF v1. It's a pain. If you don't mind the extra query, you can set the property succinctly:
int id = 1;
Order.Person = context.Persons.Where(x => x.PersonID == id).FirstOrDefault();
Entity Framework v4 will have "FK Associations", which is a fancy term for directly-settable foreign keys.
I have run into an interesting problem with Entity Framework and based on the code I had to use to tackle it I suspect my solution is less than ideal. I have a 1-to-Many relationship between Table A and Table B where entities in TableB have a reference to TableA. I have a scenario where I want to simultaneously delete all children of a row in TableA and I thought this could be achieve by simply clearing the collection:
Entity.Children.Clear()
Unfortunately, when I attempted to save changes this produced as a Foreign Key violation.
A relationship is being added or
deleted from an AssociationSet
'FK_EntityB_EntityA'. With cardinality
constraints, a corresponding 'EntityB'
must also be added or deleted.
The solution I came up with was to manually delete object via the entity context's DeleteObject(), but I just know this logic I am using has got to be wrong.
while (collection.Any())
Entities.DeleteObject(collection.First());
For one, the fact that I had to use a Where() loop seems far less than ideal, but I suppose that's purely a semantic assessment on my part. In any case, is there something wrong with how I am doing this, or is there perhaps a better way to clear a child entity collection of an entity such that Entity Framework properly calls a data store delete on all of the removed objects?
Clear() removes the reference to the entity, not the entity itself.
If you intend this to be always the same operation, you could handle AssociationChanged:
Entity.Children.AssociationChanged +=
new CollectionChangeEventHandler(EntityChildrenChanged);
Entity.Children.Clear();
private void EntityChildrenChanged(object sender,
CollectionChangeEventArgs e)
{
// Check for a related reference being removed.
if (e.Action == CollectionChangeAction.Remove)
{
Context.DeleteObject(e.Element);
}
}
You can build this in to your entity using a partial class.
You can create Identifying relationship between parent and child entities and EF will delete child entity when you delete it from parent's collection.
public class Parent
{
public int ParentId {get;set;}
public ICollection<Child> Children {get;set;}
}
public class Child
{
public int ChildId {get;set;}
public int ParentId {get;set;}
}
Mapping configuration:
modelBuilder.Entity<Child>().HasKey(x => new { x.ChildId, x.ParentId });
modelBuilder.Entity<Parent>().HasMany(x => x.Children).WithRequired().HasForeignKey(x => x.ParentId);
Trick: When setting up the relationship between Parent and Child, you'll HAVE TO create a "composite" key on the child. This way, when you tell the Parent to delete 1 or all of its children, the related records will actually be deleted from the database.
To configure composite key using Fluent API:
modelBuilder.Entity<Child>().HasKey(t => new { t.ParentId, t.ChildId });
Then, to delete the related children:
var parent = _context.Parents.SingleOrDefault(p => p.ParentId == parentId);
var childToRemove = parent.Children.First(); // Change the logic
parent.Children.Remove(childToRemove);
// you can delete all children if you want
// parent.Children.Clear();
_context.SaveChanges();
Done!