Crystal report pagination isnt working for date parameters but is with others

I have a crystal report written in CR for VS2010. The report will produce invoices over a range of either invoice numbers or dates. To that end, the report has 4 parameters (fromInvoice, toInvoice, fromDate & toDate). The stored procedure can handle nulls for any of the fields so it can receive

If I run the report with just invoice numbers the reports pagination works fine, same for invoice numbers and dates combined (and the parameters persist across the pagination). But if I search with just the from and to dates then it returns the correct number of pages (as visible in the web viewer) but when I click next then it seems to lose the date parameters and displays all the invoices produced, ever.

Any idea where I'm going wrong? why would a date parameter n开发者_如何学Cot persist when other parameters have? the report is called from the same underlying c# page.

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fixed. viewer needed viewstatemode='enabled' adding to the aspx page