I wanted to post this here for two reasons: 1) in case someone might find it useful, and 2) to see if I am missing something, or, worse, doing extra work I don't have to be doing.

So recently I defined a varchar field as PK for a table and spent a little while staring at the 'cannot convert System.DBNull to the Text property of...' error trying to figure out what to do. This is what I came up with.

Note that the last three bullet points are the only additional work on top of what you would normally do. It's just very confusing at first knowing what to change and where.

• Design table as normal in DDT, with the varchar primary key
• Don't worry about specifying a default value for the PK here
• The DDT default value only applies at the database level, which is not where the problems arise
• Create the BO in your project
• Map the BO in the mapper as you normally would
• Add the data retrieval methods to the BO as you normally would (FillAll(), etc.)
• Add a new method where you turn PK auto-incrementing off

That's it! I used this BO on a maintenance form and everything is working as it should.

As I mentioned on your other post, if you are going to be using VarChar primary keys I would create a subclassed BusinessLayer that already has the PrimaryKeyIsAutoincremented properyt set to false.  All you need to do is create a class that looks something like this:

class MyCustomBusinessLayer : MicroFour.StrataFrame.Business.BusinessLayer
{

     public MyCustomBusinessLayer()
     {
         this.InitializeComponent();
     }

     private void InitializeComponent()
     {
         this.PrimaryKeyIsAutoIncremented = false;
     }
}

Once you have a custom business layer class created, you would then change any new business objects inherited class:

• In the BO designer, set the PrimaryKeyIsAutoIncremented property to False.