make buttone invisible befour displaying crystal report

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C#

CrystalReports

on btnSave click have one crytal report on my page which is calling

btnSave.Visible = false;
 btnDelete.Visible = false;

rd.ExportToHttpResponse(ExportFormatType.PortableDocFormat, Response, true, currentsession.getMenuDescription() + TestPVNO.Text); to display the report

but befour this i want to make save button visible false
this code is displaying report but not making but invisible