SSRS hiding groups conditionally

it depends on what you are grouping by. The wholereport is suppose to be based on the group of what you want and of the report.
If there is no group data then there should be no report.

What do you mean "it depends on what you are grouping by"? I am grouping on a particular field in my dataset. I think you may have misunderstood my question. I want to see all transactions for a particular customer and am gouping by customer. If there are no transactions for that particular customer, it is still showing a line with the customer name.

So, as I stated in my original question: how to hide a group header if there are no detail rows for that group?

Then you need something like this on the header row, hide visiblty properties box..
=IF Trim(Fields!customer.name=""), True, False)

That is good for  whole customer, But for no data you would need to check a field that you have in your detail that could have no data..
=IF Trim(Fields!Product.name=""), True, False)

Your solution is not working. I put an expression on my header row visibility:

=iif(Trim(Fields!SalesNumber.Value =""), True, False)  

Fields!SalesNumber.Value is a field from my detail line. It is still showing the blank lines with customer name when there is no detail.

Does anyone else know how to do this?

I was thinking that you may have to do the same expression in the header and the detail row.
=iif(Trim(Fields!SalesNumber.Value =""), True, False)

Let me see if I understand the problem.  The report groups by customer.  Your data set returns all customers even if they havent made a purchase. You want to filter out customers in your table who have not made a purchase?  If so add a filter to the table to say sum(purchases) > 0.  Then those customers without a purchase will be excluded from the report and you wont have any group headers without any data.

No one with knowledge of how to fix this issue responded to my post.