The workflow engine is giving me quite a few headaches currently, but I'm peeling away the layers to try and figure out what's going on and where I (most likely) went wrong.

One thing I've run across, and don't understand, is in the ValidateWorkflow method.

Early in the method, there's a check to see if OriginalItem is equal to null. If it is, the program throws an exception.

Based on the explanation in the book, OriginalItem is only of concern if the item has already been submitted and is in the workflow process. I can understand the null check on it - but why throw the exception?

Wouldn't it be easier to simply do a not equal to null check - if true, do the checks against original items, if not true nothing to worry about?

Tim

Hi Tim,
The ValidateWorkflow uses the OriginalItem object to check that the read only fields were not changed. It is true that this only applies when a request has already been submitted. I'm checking this in the ValidateWorkflow method so it forces the UI to pass in this property so if at a later time I needed this when submitting a request I would have to change all the UI pages that use a workflow object.
I throw and exception because if the code reached that path then it is a coding error and the user can not correct the problem. An email is sent to the administrators whenever an exception occurs so the developer would be notified. I like to throw exceptions when the developer has to change something and it is out of the user's control. I send back validation errors when the user can take action themselves and correct the problem.

Hi Vince -

Thanks for the reply. Your approach makes sense.

I was stumped because I couldn't find out where OriginalItem was being set - it wasn't being set at the business layer or the data layer. Your reply prompted me to look in the UI, which is where it is set.

I'm using my own pages in my application, basing the first one on PTORequest.aspx. I looked at the code-behind for your page this morning, and get this portion of the picture now. I ommitted the OriginalItem portion of the code from my page, thinking I didn't need it. The hazards of jumping in half-baked :) (but I learn much better by doing then just by reading).

Tim