By using this method, we have added a coupling to the process class structure by means of the binding to the UI builder. In order to avoid this, we would use inheritance to define a data contract base class and extend it for the purposes of this binding.

The process may seem a little complicated at first but, when we break this down, it will become clearer what is actually happening.

The first task was to declare to the DialogField variables that we want added to the resulting dialog, and then to bind them to the data contract data methods. However, in order for this to work, we had to bind the UI builder class to the data contract. We did this by adding the SysOperationContractProcessing attribute to the data contract.

Once this is done, the DialogField variables are now bound to the data contract methods. We then wrote a method to validate the vehicle group control, and bound this to the control's validate event using the control's registerOverrideMethod method.

Once this is all done, the dialog created by the framework can be validated interactively, allowing the user to correct any errors without having to start again.