I think your problem is that you are conceptually thinking of processing the data manually as if you were looping through the database and passing each customer to the report. Instead, get rid of the filters on the Customer GUID and just pull all the customers over. As long as you have a Group in Crystal Reports based upon Customers.ID, then it will separate all the detail records for you and associate them to the proper group.

Also, rather than using two datasets, you could use a single Command object and use the JOIN statement to pull the customer header and detail records into a single dataset. It's faster that way since SQL does the work of joining the records and all Crystal Reports has to do is group and print them.

Hmm.. Don't know about the error you are getting, but it sounds like a NULL value is going into a field that doesn't allow nulls. Something inside the dataset schema must not allow nulls. But I don't know why you are using datasets. I only do that for complex SQL or when I have to massage the data manually prior to passing it to the report. If you're just pulling basic data from a table then I would do it with OLE DB with a DSN-less connection and let Crystal Reports worry about opening the connection and reading the database. This is much easier unless you have a special requirement that I don't see listed here.

Re your report structure, a parent-child report is pretty simple once you've done it once. Just select the tables in Crystal Reports and link them together. Put the customer Id as the group field and put the child records in the detail section. From what I've read of your post, doing subreports is overkill right now. You only need that if you are pulling from two separate child tables.

Glad it worked! You can switch reports between different servers, but it takes code and more testing. You are better off just developing for the production server from you desktop if its not too inconvenient.

Switching from the dev server to production server isn't a big deal. You just need to write a few lines of code to do it (I have examples in my .NET book). It's just easier if you don't have to.

Glad you like the forum! Feel free to post some tips when you can. I can always use the help.