See if this resolves, in this export, a class of options is used for the export. In it the DiskFileName property is the name of the file.
ExportOptions CrExportOptions ;
DiskFileDestinationOptions CrDiskFileDestinationOptions = new DiskFileDestinationOptions();
PdfRtfWordFormatOptions CrFormatTypeOptions = new PdfRtfWordFormatOptions();
CrDiskFileDestinationOptions.DiskFileName = "c:\csharp.net-informations.pdf";
CrExportOptions = cryRpt.ExportOptions;
{
CrExportOptions.ExportDestinationType = ExportDestinationType.DiskFile;
CrExportOptions.ExportFormatType = ExportFormatType.PortableDocFormat;
CrExportOptions.DestinationOptions = CrDiskFileDestinationOptions;
CrExportOptions.FormatOptions = CrFormatTypeOptions;
}
cryRpt.Export();