Get entity navigation properties after insert
As you are creating your reward
object as new Reward()
, EF doesn't have a proxy. Instead, create it using DbSet.Create like this:
var reward = context.Set<Reward>().Create();
reward.CampaignId = 5;
context.SaveChanges();
Next attach it to your DbSet:
context.Rewards.Attach(reward);
Finally, you can now use lazy loading to get related entities:
var campaign = reward.Campaign;
If I understand you correctly, you're trying to eagerly load a complex property after establishing a relationship via a foreign key property.
SaveChanges()
does not do anything in the way of loading complex properties. At most, it is going to set your primary key property if you're adding new objects.
Your line reward = context.Set<Reward>().SingleOrDefault(a => a.Id == reward.Id);
also does nothing in the way of loading Campaign
because your reward object is not attached to the context. You need to explicitly tell EF to load that complex object or attach it then let lazy loading work its magic.
So, after you context.SaveChanges();
you have three options for loading reward.Campaign
:
Attach()
reward to the context so thatCampaign
can be lazily loaded (loaded when accessed)context.Rewards.Attach(reward);
Note: You will only be able to lazy load
reward.Campaign
within the context's scope so if you're not going to access any properties within the context lifespan, use option 2 or 3.Manually
Load()
theCampaign
propertycontext.Entry(reward).Reference(c => c.Campaign).Load();
Or if
Campaign
was a collection, for exampleCampaigns
:context.Entry(reward).Collection(c => c.Campaigns).Load();
Manually
Include()
theCampaign
propertyreward = context.Rewards.Include("Campaigns") .SingleOrDefault(r => r.Id == reward.Id);
Although, I'd suggest
Load
since you already havereward
in memory.
Check out the Loading Related Objects Section on this msdn doc for more information.
In addition to Carrie Kendall and DavidG (in VB.NET):
Dim db As New MyEntities
Dim r As Reward = = db.Set(Of Reward)().Create()
r.CampaignId = 5
db.Reward.Add(r) ' Here was my problem, I was not adding to database and child did not load
db.SaveChanges()
Then, property r.Campaign
is available
I have a simple Solution around the problem.
instead of adding the CampaignID to the reward, add the campaign Object.. so:
var _campaign = context.Campaign.First(c=>c.Id == 1);//how ever you get the '1'
var reward = new Reward { Campaign = _campaign };
context.Set<Reward>().Add(reward);
context.SaveChanges();
//reward.Campaign is not null
Entity framework does all the heavy lifting here.
You're probably thinking that it's a waste to load the entire Campaign object but if you are going to be using it (from what it looks like, seems you are) then I don't see why not. You can even use the include statement when fetching it above if you need to access navigation properties from the Campaign object...
var _campaign = context.Campaign.include(/*what ever you may require*/).First(c=>c.Id = 1);