sorting and paging in gridview

[yefei]

i have a grid view, with two hyperlink fields declared decratively, and
few bound fields added dynamically in my code
i have enabled the sorting and paging for the gridview, and also
declared sort expression programmatically.
but when i rendered the grid view and click the column header, the
girdview just gone, like rendered without any data
it is the same situation when i click page index other than 1.

Price.SortExpression = "Unit Price";//for bound field

Do I have to handle the pageindexchange or sorting event
programmatically, or need other settings?

[yefei]

i checked the pages again when running
actually it can do sorting and expression
i add a 'Search' button to add all the parameters for the select comand
of the sqldatasource
if i click the column header to sort or page index to go to other
pages, the Gridview gone away, but if I press the Search button again,
it shows the sorted page ot the new page

is there some parameter that i need to set it to avoid the temporary
disappearing gridview?