Hello,

I have MQ SQL database, application working with it via EntitySpaces layer, set of es classes egenrated against this MS SQL database.

Now I have to use this application against Oracle database (db schema is fairly same except GUID primary keys which are replaced by strings in Oracle database).

The very first question: will these classes (i.e. es classes generated against MS SQL database) work transparently against Oracle database if we just replace provider settings in app.config settings? I'd like to have same code base (there is much added/customized in Custom partial classes for some bussiness logics) or should I generate es classes against Oracle db and have separate branches?

David and I posted at the same time almost ;) It's always better to know that you have to write a cross db application before you start so that you can choose columns that match on all db systems, but I may have found a way for you. Unfortunately, GUID is one of the very few that doesn't port well (Amazing isn't it, you'd think by now these other systems would have it, it's to valuable not to have).

Here is a post on our mutli-provider mode ==> POST

Our Database Independent feature is pretty good and can degrade gracefully on columns that aren't exact matches, i.e. an 'int' can be used for a 'bit' and so on. You could possibly pull this off however on Guids.

Suppose you generate against SQL as your master and you have a string of the proper length to hold the guid in Oracle as your PK. You run our extra Metadata map class against Oracle, the property for those columns will have been defined by SQL and be a guid. You can easily test this out in a quick sample app by following the instructions in the linked post. I'd create a quick little test app and use a single table in SQL and Oracle to test this. Use SQL as your master so your properties are of type guid then overload the PK property in your entity's custom class like so:

I would be very interested to see how this works for you. 

namespace BusinessObjects
{
    public partial class Customers : esCustomers
    {
        // Override our PK property
        public override Guid? CustomerID
        {
            get
            {
                if (this.Row == null)
                {
                    this.AddNew();
                }

                object o = this.Row[CustomersMetadata.ColumnNames.CustomerID];
                if (o is string)
                {
                    // It must have come from Oracle, convert it.
                    return new Guid(o);
                }
                else
                {
                    // It's already a guid.
                    return (Guid?)o;
                }
            }
            set
            {
                base.CustomerID = value;
            }
        }
    }
}

David, Mike - thank you very much. I'll try to manage it this week using your tips and links and get back here to let you know how it works for me once I have any results.

Mike.Griffin:

It's always better to know that you have to write a cross db application before you start so that you can choose columns that match on all db systems,

Sure it's true, but first I wasn't as familiar with Oracle as with MS SQL and the fact that Oracle didn't have GUIDs was a big surprise for me I started with MS SQL and did expect various kind of problems with Oracle in future but not things like this one...