views:

4529

answers:

3

As the result of a form post, I'm trying to save a new Brand record. In my view, Gender is a dropdown, returning an Integer, which is populated from ViewData("gender")

I've setup my link as follows:

gID = CInt(Request.Form("Gender"))
Brand.GenderReference.EntityKey = New EntityKey("DB_ENTITIES.Gender", "Id", gID)
TryUpdateModel(Brand)
DB.SaveChanges()

Which results in the following error.

Entities in 'DB_ENTITIES.Brand' participate in the 'FK_Brand_Gender' relationship. 0 related 'Gender' were found. 1 'Gender' is expected.

Could someone explain the parameters in plain english to me. I've also tried DB.Gender as the first parameter but no joy.

A: 

What you need is an instance of both Brand and Gender and then set Brand.Gender to the instance of the Gender. Then you can save without problems.

Jonathan van de Veen
Does that not involve a round trip to my DB? Surely the View is posting back an ID that can be tied up.
Paul
It depends, if the objects are already in the context, it does not require a trip to the db. Alex James code is good to use (it pretty much does as I wrote).
Jonathan van de Veen
A: 

Ok heres what I've come up with instead of using updateModel. It appears to be problematic / potentially a security risk anyway with potentially additional fields being added in the post. A New instance of Gender can be instantiated via trygetObjectByKey. This is working so far. Any other suggestions on getting UpdateModel to update the Gender property object appreciated.

Dim cID As Integer
cID = CInt(Request.Form("Gender"))
Dim key As New EntityKey(DB.DefaultContainerName() & ".Gender", "ID", cID)

Dim objGenderDS As New Gender
'Bring back the Gender object.
If DB.TryGetObjectByKey(key, objGenderDS) Then
Brand.GenderReference.EntityKey = key
Brand.Gender = objGenderDS
DB.AddToBrand(Brand)
DB.SaveChanges()
Else
End If
Paul
+5  A: 

Rather than creating an EntityKey create a stub Gender object (sorry I'm not a VB guy so in C#):

Gender g = new Gender{ID = Int32.Parse(Request.Form("Gender"))};

Then you attach the Gender to the appropriate EntitySet (the name of property on DB that you get Gender entities from is the string below):

DB.AttachTo("Genders",g);

This puts the database in the state where the Gender is in the ObjectContext in the unchanged state without a database query. Now you can build a relationship as per normal

brand.Gender = g;
DB.AddToBrand(brand);
DB.SaveChanges();

That is all there is to it. No need to muck around with EntityKeys

Hope this helps

Alex

Alex James
Thanks for the response Alex - getting this now:An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key.
Paul
Paul, how did you solve the 'multiple objects with the same key' issue? I am getting the same.
Picflight
Before attaching something to the context you should check the ObjectStateManager using LINQ to Objects to check that the same object isn't already there.
Alex James