export crystal report to PDF

[meydz]

I am creating a report in crystal and export it to pdf at runtime. Below is the sample code

DiskFileDestinationOptions diskDestination = new DiskFileDestinationOptions();

reportDocument.ExportOptions.ExportDestinationType = ExportDestinationType.DiskFile;

reportDocument.ExportOptions.ExportFormatType = ExportFormatType.PortableDocFormat;

string fileName = "C:\\reportsample.pdf";
diskDestination.DiskFileName = fileName;

reportDocument.ExportOptions.DestinationOptions = diskDestination;

reportDocument.Export(); //this line triggers the error
reportDocument.Close();

the exception is :
Error in File C:\WINNT\TEMP\temp_1066b89b-658b-495b-ab56-27a343805d6d.rpt: Access to report file denied. Another program may be using it.

Is there anyone who knows how to get over it?
Thanks! Any help would be highly appreciated.