It is now time to create the first real page, the Contacts Form, and the database tables to support it.

But there is a problem. I use LLBLGen, an Object Relational Mapper, which maps my database tables to classes. It creates a number of classes:

• Entity classes – the classes which map to the tables
• Collection classes – collections of entities
• Typed List classes – read only lists which include the specific fields from tables or relations that I might want to use, for example in list boxes
• Classes formed from relationships that I establish
• Various factory and helper classes for sorting, filtering and other assorted functions.

While there is no problem with the Contact entity, or table, that I will create, It is worthwhile mentioning here the procedure that I follow.

Data is held in a relational database, which follows fairly strict rules. Relational databases can be described in purely mathematical terms, and there is a well-deveoped relational theory to support them.

But the object which I use to populate the controls on the forms, such as text boxes, list boxes, etc, do not necessarily relate 1 to 1 with the tables. So my thinking is in terms of the objects and classes, but my O/R mapper does not translate classes into data tables, rather it maps data tables onto classes.

So I need to consider, first what objects I want to show, and from those determine the data that is needed to create these objects. Once that is done I can then apply relational theory to create the database tables. The O/R mapper then generates my classes which I use to create the objects.

As I said earlier, it is not a problem with the Contacts table or classes. I will create a table for Contacts and map it directly to a Contacts entity.

The Contacts table will consist of the following fields, or attributes, or columns, depending upon your prefered nomenclature – isn’t that a great word!

• ContactID, the primary key and we will make it autoincrement
• CompanyName
• Surname – the surname of the contact person within the company
• FirstName
• Add1 – the street number and name, or post office box
• Add2 – the town or suburb
• Postcode
• State – that is geographical state, like NSW, VIC etc
• Phone
• Mobile
• Email

I have realised that I left fax out of this. I have already built the form, but I have made a note to amend it, at some stage soon.

The next thing to do is to create the form, the subject of the next article.