Entity Framework Complex Relationships

Apocolypse2005 · June 23rd, 2012, 08:58 AM

I have a complex relationship in my Database.

Code:

Packages (packageID, package_name , .... )
VariantPackage (packageID, variantID)
Variant (variantID, variant_name, .... )
ProductVariant (variantID, productID)
Product (productID, product_name, .... )

(I take it you can assume the ID fields are Primary or Foreign respectively?)
The entity framework has elegantly picked up on this because if do this:

Code:

Package newPackage = new Package()
{
 packageID = Guid.NewGuid()
 etc . . .
};

Variant newVariant = new Variant()
{
 variantID = Guid.NewGuid()
 etc . . .
};

I get the option when doing this line below to add the variant to that package

Code:

newPackage.Variant.AddObject(newVariant);
_db.Package.AddObject(newPackage);
_db.SaveChanges();

Now when I SaveChanges will that in those 2 lines, create entries in all 3 tables? If I have set up the model correctly?
Thanks

Imar · June 23rd, 2012, 10:49 AM

Quote:

Now when I SaveChanges will that in those 2 lines, create entries in all 3 tables? If I have set up the model correctly?

Why don't you try it out? Easiest way to tell....

It should do it, provided the VariantPackage only has the two mentioned foreign keys.

Imar

Apocolypse2005 · June 23rd, 2012, 11:05 AM

Yeah, I've been a bit apprehensive about testing it out!

Imar · June 23rd, 2012, 11:13 AM

Why? You could create a simple demo project with a new clean database to see how it behaves...

Imar

Apocolypse2005 · June 23rd, 2012, 11:16 AM

Is it allowed to DetectChanges() and SaveChanges() after all the creation of the products and variants and package has been done?

Imar · June 23rd, 2012, 11:24 AM

If this is a Database First model, you shouldn't have to call DetectChanges as SaveChanges will figure that out for you.

Can you be more explicit about what you're asking and why? Is it not working?

Imar

Apocolypse2005 · June 23rd, 2012, 12:03 PM

I'm just about to test to see if it works. I'm just a tad new to this entity framework stuff, I've got a book under my nose and I was just wondering if my theory was correct!

Apocolypse2005 · June 23rd, 2012, 02:15 PM

I get this error after executing the SaveChanges(); (this is preceded by DetectChanges();)

Code:

An object with the same key already exists in the ObjectStateManager. The existing object is in the Unchanged state. An object can only be added to the ObjectStateManager again if it is in the added state.

Imar · June 23rd, 2012, 02:21 PM

Have you tried removing the call to DetectChanges as I suggested in a previous post?

Imar

Apocolypse2005 · June 23rd, 2012, 02:31 PM

It doesn't get that far, it does this:

Code:

 foreach (object[] idQuant in prodList)
            {
                Guid prodId = Guid.Parse((string)idQuant[0]);
                newVariant.VariantProducts.Add(new VariantProduct(){
                    variantID = newVariant.variantID,
                    productID = prodId,
                    quantity = (int)idQuant[1]
                });
            }

            Guid packageID =  Guid.Parse(AddPackageList.SelectedValue);
            // 081-0f46219e1c0d
            IQueryable<Package> result = ptx.Packages.Where(o => o.packageID == packageID);
            Package firstOne = result.First<Package>();
            firstOne.Variants.Add(newVariant); 
            ptx.Packages.AddObject(firstOne); //GETS HERE its because there is already a package object in the database, i just want to update it