using System.IO;
MemoryStream oStream;
oStream = (MemoryStream)rpt.ExportToStream(CrystalDecisions.Shared.ExportFormatType.PortableDocFormat);
Response.Clear();
Response.Buffer = true;
Response.ContentType = "application/pdf";
Response.AddHeader("content-disposition",
"filename=" + FileName + ".pdf");
Response.BinaryWrite(oStream.ToArray());
Response.End();