Eager loading for properties of derived classes
In entity framework there should be a way to eager load (include) navigation properties of a derived class.
When in an data model for entity framework has a navigation property it is not posseble to eager load that navigation property besides when using OfType<> or when eager loading the derived type itself by a navigation property.
This could be done by using a special syntax of the include path.
Since a property of the base class can not have the same name as the derived class, it would also be possible to navigate to the derived class by its name.
e.g.: If class Derived inherits from Base and has a navigation property named Prop one could say
dbContext.BaseSet.Include("Derived.Prop")
this should query all entities of type Base and eager load property Prop for all instances of Derived in the reslult list
Christof Nordiek
shared this idea
Issue tracking this feature: https://github.com/aspnet/EntityFramework/issues/3910.
21 comments
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Ciaran Colgan
commented
Not a solution but a workaround. Use a Select projection on your IQueryable, with the derived type accessed by: "DerivedTypeDto = (x as DerivedType)"
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b
commented
Eager loading of N:1 makes sense. What is not acceptable is to have 5-10 related properties, doing 5-10 round trips to the database because you can't get this all in a single trip. This although has to be configurable (for some N:1 relations you might not want this).
Also defining eager load of some 1:N relations (when you know there won't be more than 10-50 items per aggregate) does make a sense. It's still better than the N+1 select issue from lazy-loading.
EF7 1.1 - still behind NH2.x (released at 2008) or NH3.0(2010)...
If there would be a real open-source competition, EF7 would have the same fate as of Unity.
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fsgfdgdfgsdf
commented
Still waiting... six years later, sigh.
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Anonymous
commented
i have barely used entity and this is enough to stop be dead in my tracks.
once again i drop entity to a shinny pamphlet
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Anonymous
commented
SHOW STOPPER!!
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Leroy
commented
I was quite impressed by the whole inheritance support in EF, only to find out weeks later that it's a half baked solution.
This was reported in 2010.. how can this still not be implemented yet?
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Fabrizio Hernandez
commented
I need it all the time. I'm currently hitting my head on my desk for this exact issue.
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Levi Hobbs
commented
This is absolutely ridiculous. I guess no one in the world uses inheritance. It's a totally new thing.
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Eric
commented
Hmmm 386 votes and this moves from "under review" to "no status". I certainly hope this becomes a priority at some point. The current solution is terribly inefficient.
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Ran Davidovitz
commented
This is a must in real life scenarios (not the simple demos). today i was forced to remove inheritance!!
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Hitesh
commented
It should also support navigation properties of navigation property
For example, Orders -> OrderDetails -> ItemsElectronicItem derives from Items
ElectrionicItem -> MoreDetailsHence, it will be
Orders -> OrderDetails -> ElectronicItem (Items) -> MoreDetails
Now, I want to retrieve Order including all navigation properties
e.g.
context.Orders.Include("OrderDetails").Include("OrderDetails.Items").Include("OrderDetails.Items.MoreDetails"); -
shimmy
commented
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M. Holmgren
commented
No, eager loads should be explicit.
However, there should be support for including sub type property navigation includes which today forces multiple queries
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M. Holmgren
commented
Context.CreateObjectSet<BaseType>.Where(o => o ...).Include("BasetypeNavigationProperty").Include<Subtype1>("SubTypeNavigationProperty").Include<Subtype2>("OtherSubtype2Property")
This is what I want in an eager load query
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Francis Ouellet
commented
If I have this :
Invoice 1 -- * Amounts
Amounts -> UnitTax or FeeI want to load invoice and his dependances
IQueryable<Invoice> query = from f in context.Set<Invoice>()
.Include("Amounts")
.Include(f => (f.Amounts as UnitTax).UnitTaxDetail)
.Include(f => (f.Amounts as Fee).FeeDetail)
where f.ID.Equals(id)
select f;Not working!
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Bruno de Souza Melo
commented
Solution.
The derived type it's applied only for Conceptual Data Model (Entity Data Model). Remove any foreignkey of your derived physical table.
Ex.:
Car - IDCar, Name
SportCar - IDCar, WheelsType
Remove the foreignkey (don't remove the column just relationship for using on Mapping Detail) of SportCar and set BaseType to Car in Entity Data Model.
See the article association with derived types.
http://msdn.microsoft.com/en-us/library/dd163157.aspx
Thank you.
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Bruno de Souza Melo
commented
Solution.
The derived type it's applied only for Conceptual Data Model (Entity Data Model). Remove any foreignkey of your derived physical table.
Ex.:
Car - IDCar, Name
SportCar - IDCar, WheelsType
Remove the foreignkey (don't remove the column just relationship for using on Mapping Detail) of SportCar and set BaseType to Car only in Entity Data Model.
See the article association with derived types.
http://msdn.microsoft.com/en-us/library/dd163157.aspx
Thank you.
-
Bruno de Souza Melo
commented
It's so necessary!!
Some like this dbContext.BaseSet.Include<DerivedType>("Navigation").
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Bruno de Souza Melo
commented
Very useful!!
I agree it would be nice to have a way to eager load on a navigation property in a derived type. Here is some tentative syntax for it with lambda expressions:
var peopleAndManagers1 =
from p in context.People.Include(p => (p as Employee).Manager)
where p.LastName.StartsWith("a")
select p;Or alternatively:
var peopleAndManagers2 =
from p in context.People.Include<Employee>(e => e.Manager)
where p.LastName.StartsWith("a")
select p; -
rbetm
commented
Having the ability to eager load derived properties (provided you know and supplie their names) would be very useful. Unfortunately, I can't vote for this suggestion as I don't agree with the IncludeAll...