Trouble inheriting from another entity

I'm having trouble configuring entity relationships when one entity inherits from another. I'm new to ADO Entity Framework -- perhaps someone more experienced has some tips for how this is best done. I'm using .net 4.

Database tables with fields:

• Products (int ID, nvarchar Description)
• FoodProducts (int ProductID, bit IsHuge)
• Flavors (int ID, int FoodProductID, nvarchar Description)

There are constraints between Products and FoodProducts as well as FoodProducts and Flavors.

Using the designer I create a model from the database. The designer seems to get it right, with a 1:0..1 association between Product and FoodProduct entities, and 1:* association between Flavor and FoodProduct. No errors when I save or build.

Next I set FoodProduct entity to inherit from Product entity. Then I get errors concerning relationship between Product and FoodProduct. Ok, starting fresh, I first delete the relationship between Product and FoodProduct before setting the inheritance. But now I get errors about the relationship between FoodProduct and Flavor. So I delete and then recreate that relationship, connecting Flavor.ID to FoodProduct.ProductID. Now I get other errors.

My question is this: Should I instead be creating relationship between Flavor.FoodProductID and Product.ID? If so, I assume I then could (or should) delete the FoodProduct.ProductID property. Since my database will have many of these types of relationships, am I better off first creating the entity model and exporting the tables to SQL, or importing the database schema and then making many tweaks?

My intent is that there will be several types of products, some of which require many additional fields, some of which do not. So there may be zero or one FoodProducts records associated with each Product record. At least by my thinking, the table for each sub-type (FoodPro开发者_运维百科ducts) should be able to "borrow" the primary key from Products (as a FK) to uniquely identify each of its records.

You can find a screen capture here: http://img218.imageshack.us/img218/9720/entityframework.jpg (I'd embed the img but haven't earned the requisite rep' yet!)

Well, I deleted the FoodProduct.ProductID field, as it should always return the same value as Product.ID anyway. Then, as you hinted, I had to manually map the Products.ID field to FoodProducts.ProductID field. Errors resolved. I'll write a little code to test functionality. Thanks for the "observations"!

Couple of observations:

FoodProducts needs a primary key (e,g identity - FoodProductID). Are you sure it should be a 1:0..1 between Food and FoodProducts? I would have thought it should be 1:0..*. For this cardinality to work you need a unique PK on this table.

When you setup inheritance for entities, the parent entity's properties are inherited. So FoodProducts will inherit ID from the Product table.

BUT, on the physical model (database), this field still needs to be mapped to a column on the FoodProducts table - which is why you need the identity field.

After you setup inheritance, you still need to map all the columns on the derived tables. My money is on you have not mapped "ID" on FoodProducts to any column.

If you screencapped your model and show the errors you are getting it would be much easier to diagnose the issue.