he report definition above, a QueryFormat is used.</p>
 
<p>The Query method returns the query by using _report.GetParamsWhere to build the where clause for the restriction on the invoice field.  In order to use _report.GetParamsWhere, the ParamsSelectControl must be used for the fields passed to GetParamsWhere.  Notice the use of ParamsSelectControl for the invoice parameter in the Params section of the report.</p>

<p>Before_invoice is a method that gets called before every invoice is printed.  It returns