CODEWITHSUNDEEP
c#entity-frameworkado.netentity-framework-4.1
Sam
Sam

Reputation: 707

Reload an entity and all Navigation Property Association- DbSet Entity Framework

I have a problem with entity association refresh. When I get an entity with like this:

MyContext context = new MyContext();

Person myPerson = context.PersonSet.FirstOrDefault();
String myPersonName = myPerson.Name;
Address myPersonAddress = myPerson.Address;

I got an a person with an association named Address and a property named Name. If I modify manually the datas in database for example the property Name, I have to use the following code to reload my entity:

context.Entry(myPerson).Reload();

and I have the new value for Name. But If I do the same for Address it doesn't work. I think it is because Address is an association property. I need to refresh it.

How Can I do to force the reload of Address association (and all other association in Person class) ?

EDIT:

In the same case, a person can have more than one address. 

MyContext context = new MyContext();

Person myPerson = context.PersonSet.FirstOrDefault();
String myPersonName = myPerson.Name;
List<Address> myPersonAddresses = myPerson.Addresses;

In this case, it is not a Reference:

context.Entry(myPerson).Reference(p => p.Address).Load();
// Address will be populated with only the new address
// this isn't required because I use lazy loading

but a Collection:

context.Entry(myPerson).Collection(p => p.Addresses).Load();
// Address will be populated with old value and new value

I need to use this to work: 

context.Entry(myPerson).Collection(p => p.Addresses).CurrentValue.Clear();
context.Entry(myPerson).Collection(p => p.Addresses).Load();

But it doesn't seem to be a good solution to do this for all my navigation properties!

Upvotes: 40

Views: 38742

Answers (5)

bambams
bambams

Reputation: 765

Using Entity Framework 6 and classic .NET (not .NET Core), I needed to reload a navigation property collection after the records had been updated by a stored procedure call.

What worked (without hammering the database with commands, as would happen iterating over the collection and calling context.Entity(e).Reload() for each element) was to iterate over the collection and assign the EntityState.Detached state to context_.Entity(e).State, and then using context.Entity(p).Collection(o => o.Navigations).Load() to reload the collection from the DB.

public void ReloadFooThings(Foo foo)
{
    foreach (var thing in foo.Things.ToList())
    {
        context_.Entry(thing).State = EntityState.Detached;
    }

    context_.Entry(foo).Collection(o => o.Things).Load();
}

Note that any changes you had made to the entities would be overwritten in this scenario, so they would have to be saved before changes were made from another context or direct SQL access.

It should be possible to define this with generics to achieve a library call for any navigation collection, but I didn't have time to work out the loop using the navigation property Expression<Func<TEntity, ICollection<TElement>>> to access the underlying collection to iterate over for detaching.

Upvotes: 0

Satria
Satria

Reputation: 326

If it gained one entry, only your .Load() method helped.

context.Entry(myPerson).Collection(p => p.Addresses).Load();

If p.Addresses lost one entry, it can be refreshed by

((IObjectContextAdapter)CurrentContext(context)).ObjectContext.Refresh(RefreshMode.StoreWins, p.Addresses);

Upvotes: 13

Slauma
Slauma

Reputation: 177133

If you don't use lazy loading, you have the load the new Address explicitly (as you had to load it explicitly (with Include, for example), when you loaded the Person initially):

context.Entry(myPerson).Reload();
// If the person refers to another Address in the DB
// myPerson.Address will be null now

if (myPerson.Address == null)
    context.Entry(myPerson).Reference(p => p.Address).Load();
    // myPerson.Address will be populated with the new Address now

If you use lazy loading, you don't need the second code block. Nonetheless, you get a new query to the database as soon as you access properties of the new myPerson.Address (like you have a new query in the second code block above) because the first line will mark the navigation property as not loaded if the person refers to a new address in the DB.

This behaviour doesn't depend on whether you have exposed the foreign key in the model class or not.

There doesn't seem to be a way to call some single magic Reload method which would reload and update the whole object graph in one call (similar like there is no single Include to eager load a complete object graph).

Upvotes: 33

specialist
specialist

Reputation: 7

I've solved this problem with using Detach before reading object from dbContext. This method allowed me to refresh all navigation properties of the object. I've described my scenario and details of solution here Entity Framework: Reload newly created object / Reload navigation properties

Upvotes: -3

ALT
ALT

Reputation: 1242

You need to use Query() extension to modify your LINQ expression. Here it is an example on basis of my personcal code. In this code I reload Addresses collection with related AddressType navigation property for myPerson object and place the result into SomeList:

_DbContext.Entry<Person>(myPerson)
          .Collection(i => i.Adresses) // navigation property for Person
          .Query()
          .Include("AddressType")        // navigation property for Address
          .OrderBy(i => i.Name)
          .ThenBy(i => i.AddressType.AddressTypeName) // just an example
          .Select(i => new someClass
          {
              SoomeField1 = i.SomeField1,
              ...
          })
          .ToList()
          .ForEach(i => SomeList.Add(i)); // SomeList is a List<T>

Upvotes: 2

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