My attempt at creating an excel Sheet. Error in saveas. HELP

Question

This is my attempt at creating an excel sheet from in asp.net with C#. I think I'm close to getting there. I got most of this code from eggheadcafe. The line oWB.SaveAs(...) always throws this error Error: Object reference not set to an instance of an object. Line: Interop.Excel Anyone see what the hell is wrong private void Page_Load(object sender, System.EventArgs e) { string strCurrentDir = Server.MapPath(".") + "\\"; RemoveFiles(strCurrentDir); // utility method to clean up old files Excel.Application oXL; Excel._Workbook oWB; Excel._Worksheet oSheet; Excel.Range oRng; try { oXL = new Excel.Application(); oXL.Visible = true; //Get a new workbook. oWB = (Excel._Workbook)(oXL.Workbooks.Add( Missing.Value )); oSheet = (Excel._Worksheet)oWB.ActiveSheet; //Format A1:Z1 as bold, vertical alignment = center. oSheet.get_Range("A1", "Z1").Font.Bold = true; oSheet.get_Range("A1", "Z1").VerticalAlignment =Excel.XlVAlign.xlVAlignCenter; //AutoFit columns A:Z. oRng = oSheet.get_Range("A1", "Z1"); oRng.EntireColumn.AutoFit(); oXL.Visible = true; oXL.UserControl = true; string strFile ="report" + System.DateTime.Now.Ticks.ToString() +".xls"; strFile = strCurrentDir + strFile; oWB.SaveAs( strFile,Excel.XlFileFormat.xlWorkbookNormal,null,null,false,false,Excel.XlSaveAsAccessMode.xlShared,false,false,null,null,null); //Need all following code to clean up and extingush all references!!! oWB.Close(null,null,null); oXL.Workbooks.Close(); oXL.Quit(); System.Runtime.InteropServices.Marshal.ReleaseComObject (oRng); System.Runtime.InteropServices.Marshal.ReleaseComObject (oXL); System.Runtime.InteropServices.Marshal.ReleaseComObject (oSheet); System.Runtime.InteropServices.Marshal.ReleaseComObject (oWB); oSheet=null; oWB=null; oXL = null; GC.Collect(); // force final cleanup! string strMachineName = Request.ServerVariables["SERVER_NAME"]; Label1.Text="Download Report"; } catch( Exception theException ) { String errorMessage; errorMessage = "Error: "; errorMessage = String.Concat( errorMessage, theException.Message ); errorMessage = String.Concat( errorMessage, " Line: " ); errorMessage = String.Concat( errorMessage, theException.Source); Label1.Text= errorMessage ; } }