I'd like to update the entity type, but couldn't find the request to do so. It may not be possible, but I don't understand the reason.
I tried updating the entity type with IoTA. The IoTA was updated but Orion was not.
Then I found this answer: FIWARE Orion: change entity type
I dont understand the funcionality of entityType. Why is inmutable?
Thanks.
The combination of entity id and entity type compose the identification of an entity. They are like the "primary key" of the entity.
The identification of the entity is immutable. Thus, neither id nor type can be changed. There is no operation in the NGSIv2 API to do so.
A possible workaround is to recreate the entity with a different type. Something like this (pseudo-code):
oldEntity = GET /v2/entities/<id>?type=<oldType>
newEntity = oldEntity
newEntity.type = newType
POST /v2/entities (using newEntity as payload)
Related
Having two entities defining relationship by #ManyToOne and #OneToMany, how can I get foreign key without asking from related object and just by looking at defining tables? How do I get OWNER_ID from Owned by something like owned.getOwnerId() instead of owned.getOwner().getId() and still be able to owned.getOwner()?
Map the field in your entity as a basic mapping allows you to use the foreign key directly. You can keep the object reference mapping as well, but one of the two mappings must then be marked as insertable=false, updatable=false so that JPA knows which mapping controls the field in the event they show different values.
I have a strange problem when using Entity Framework code first.
When I return an object with dbContext.Users.Where... I don't get the User defined in my model, but User_{GUID}.
Is there anyone who knows this phenomenon and can help?
Regards,
Ajit
If your dbContext.Users if of a type DbSet<User> then you would get a User-castable type instance if you query Users collection.
User_{GUID} looks like a dynamic proxy object to a User instance in your DbContext. Treat it as if it was a User instance.
I have a problem updating a foreign key in an Entity Framework entity. I am using self tracking entities and have an entity with some relations where the foreign key is also present as a property (one of the new features of EF4). The key (an integer) is marked as Nullable and Concurrency Mode fixed.
Specifically I have an Alarm entity with a many to 0..1 relationship to a confirming user. (a user may confirm several alarms, but an alarm can be confirmed by only zero or one users).
The entity definitions (simplified):
Alarm properties
Id Int32 non-nullable identity entity key
UserId Int32 nullable concurrency mode fixed
Alarm navigation properties
User 0..1 multiplicity
User properties
Id Int32 non-nullable identity entity key
Name String non-nullable
In my self tracking entity the confirming user id is auto-generated as a Nullable just as expected, however if I assign a user to an already persistent alarm and run ApplyChanges, the self tracking context extension tries to set the original value (null) in the EF context (In SetValue in the context extensions), but silently skips that because the ClrEquivalentType of the EdmType is a non-nullable Int32.
Auto-generated extension code:
private static void SetValue(this OriginalValueRecord record, EdmProperty edmProperty, object value)
{
if (value == null)
{
Type entityClrType = ((PrimitiveType)edmProperty.TypeUsage.EdmType).ClrEquivalentType;
if (entityClrType.IsValueType &&
!(entityClrType.IsGenericType && typeof(Nullable<>) == entityClrType.GetGenericTypeDefinition()))
{
// Skip setting null original values on non-nullable CLR types because the ObjectStateEntry won't allow this
return;
}
}
int ordinal = record.GetOrdinal(edmProperty.Name);
record.SetValue(ordinal, value);
}
When the EF later tries to update my alarm I get an OptimisticConcurrencyException because it constructs a WHERE clause in the UPDATE statement where it uses 0 (zero) as the original user foreign key value instead of the correct "is null". (The WHERE clause is part of the EF optimistic concurrency mechanism, where the original values of the properties marked with "fixed" concurrency mode are checked agains the properties in the database).
Are nullable foreign keys / primitive types not fully supported in self tracking entities for EF?
If not, am I forced to use dummy entities instead of null or are there other workarounds?
Update
I have tried to reproduce the problem without STE, but plain EF seems to handle optimistic concurrency well for nullable foreign keys, so this is an STE problem, not an EF problem.
There is numerous issues with self tracking entities, so it is not surprising that there is a glitch here. If I find a workaround that can be implemented in the STE T4 script I will post it here.
Bill Huth posted a working patch at MSDN.
Yes, nullable foreign keys are certainly allowed. We use them all over the place. You don't show your database or model, so it's difficult to be certain what the problem could be, but it sounds as though the Entity Framework cannot figure out the primary key of one of the tables involved. Perhaps you don't have one, maybe because one of them is a view? I'm guessing here, because you don't give much information about what you're doing.
I am just starting to use the Entity Framework 4 for the first time ever. So far I am liking it but I am a bit confused on how to correctly do inheritance.
I am doing a model-first approach, and I have my Person entity with two subtype entities, Employee and Client. EF is correctly using the table per type approach, however I can't seem to figure out how to determine what type of a Person a specific object is.
For example, if I do something like
var people = from p in entities.Person select p;
return people.ToList<Person>();
In my list that I form from this, all I care about is the Id field so i don't want to actually query all the subtype tables (this is a webpage list with links, so all I need is the name and the Id, all in the Persons table).
However, I want to form different lists using this one query, one for each type of person (so one list for Clients and another for Employees).
The issue is if I have a Person entity, I can't see any way to determine if that entity is a Client or an Employee without querying the Client or Employee tables directly. How can I easily determine the subtype of an entity without performing a bunch of additional database queries?
Use .OfType<Client>() in your query to get just the clients. See OfType.
e.g. entities.Person.OfType<Client>() ...
Use is to test if a Person object is a specific sub-class, e.g. if (p is Employee) ...
BTW why isn't it entities.People? Did you not select the pluralization option?
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.