Question

I am using ASP.NET MVC2 in Visual Studio 2008. I believe the SQL Server is 2005.

I have two tables: EquipmentInventory and EquipmentRequested

• EquipmentInventory has a primary key
  of sCode
• EquipmentRequested has a
  foreign key called sCode based upon
  sCode in EquipmentInventory.

I am trying the following code (lots of non-relevent code removed):

        try
        {
            EChODatabaseConnection myDB = new EChODatabaseConnection();

//this section of code works fine.  The data shows up in the database as expected
            foreach (var equip in oldData.RequestList)
            {
                if (equip.iCount > 0)
                {
                    dbEquipmentInventory dumbEquip = new dbEquipmentInventory();
                    dumbEquip.sCode = equip.sCodePrefix + newRequest.iRequestID + oldData.sRequestor;
                    myDB.AddTodbEquipmentInventorySet(dumbEquip);
                }
            }

            myDB.SaveChanges();   //save this out immediately so we can add in new requests

//this code runs fine
            foreach (var equip in oldData.RequestList)
            {
                if (equip.iCount > 0)
                {
                    dbEquipmentRequested reqEquip = new dbEquipmentRequested();
                    reqEquip.sCode = equip.sCodePrefix + newRequest.iRequestID + oldData.sRequestor;
                    myDB.AddTodbEquipmentRequestedSet(reqEquip);
                }
            }

//but when I try to save the above result, I get an error
            myDB.SaveChanges();

oldData is passed into the function. newRequest is the result of adding to a “non-related” table. newRequest.iRequestID does have a value.

In looking at the reqEquip is the watch window, I do notice that EquipInventory is null.

The error message I receive is:
“Entities in ‘EChODatabaseConnection.dbEquipmentRequestedSet’ participate in the ‘FK_EquipmentRequested_EquipmentInventory_sCode’ relationship. 0 related ‘EquipmentInventory’ were found. 1 ‘EquipmentInventory’ is expected.”

Obviously I’m doing something wrong but thus far, I can not seem to find where I am having a problem.

Anyone have some hints on how to properly insert a record into a table that has a foreign key reference?

UPDATE:
I am using the Data Entity Framework.

UPDATE:
Thanks to Rob’s answer, I was able to figure out my error.
As Rob mentioned, I needed to set my reference for the foreign key.

My coding result looks like:

            foreach (var equip in oldData.RequestList)
            {
                if (equip.iCount > 0)
                {
                    dbEquipmentInventory dumbEquip = new dbEquipmentInventory();
                    dumbEquip.sCode = equip.sCodePrefix + newRequest.iRequestID + oldData.sRequestor;
                    myDB.AddTodbEquipmentInventorySet(dumbEquip);

                    //add in our actual request items
                    dbEquipmentRequested reqEquip = new dbEquipmentRequested();
                    reqEquip.EquipmentInventory = dumbEquip;
                    myDB.AddTodbEquipmentRequestedSet(reqEquip);
                }
            }

            myDB.SaveChanges();   

Does anyone see a better method for doing this?

Answer 1

What are you using as an ORM? I believe that regardless of which one you’re using, you could use the foreign key handling of most ORMs to handle this for you. For example, you make a new dumbEquip, don’t do the immediate save. Do your dbEquipmentRequested reqEquip = new dbEquipmentRequested(); and add the data to it and then say dumbEquip.dbEquipmentRequested.Add(reqEquip). Then save the record and the ORM should save the records in the correct order required for the FK and even enter the FK ID into the reqEquip record.