public static string ImportFile(string fileName)
        {
            string       retVal           = string.Empty;
            string       uploadedFilePath = string.Empty;
            eInvoiceType invoiceType;

            System.Web.SessionState.HttpSessionState currentSession = HttpContext.Current.Session;

            //Replace with system defined regular expression
            if (fileName.ToLower().Contains("hubinv"))
            {
                invoiceType = eInvoiceType.PFHubCharge;
            }
            else if (fileName.ToLower().Contains("chargeinv"))
            {
                invoiceType = eInvoiceType.PFDepotCharge;
            }
            else
            {
                invoiceType = eInvoiceType.PFSelfBillDeliveryPayment;
            }

            //Check to see if the file already exists.
            Facade.IPalletForceImportPreInvoice facPFImport = new Facade.PreInvoice();
            bool fileAlreadyImported = facPFImport.CheckImportedFiles(fileName);

            if (currentSession[vs_uploadedFilePath] != null && currentSession[vs_userID] != null && !fileAlreadyImported)
            {
                #region Import File

                uploadedFilePath = currentSession[vs_uploadedFilePath].ToString();

                if (File.Exists(uploadedFilePath))
                {
                    try
                    {
                        currentSession[vs_pfImportedInvoice] = facPFImport.ImportPalletForceInvoice(uploadedFilePath, invoiceType, currentSession[vs_userID].ToString());
                        retVal = bool.TrueString;
                    }
                    catch (Exception ex)
                    {
                        #region File Removal on Error
                        retVal = FileRemovalOnError(uploadedFilePath, ex);
                        #endregion
                    }
                }
                else
                {
                    retVal = string.Format("{0}|{1}", 4, -1);
                }

                #endregion
            }
            else
            {
                #region Remove and send Error Message

                if (currentSession[vs_uploadedFilePath] != null)
                {
                    try
                    {
                        File.Delete(currentSession[vs_uploadedFilePath].ToString());
                    }
                    catch (Exception ex) { }
                    finally
                    {
                        retVal = fileAlreadyImported ?  string.Format("{0}|{1}", 3, -1) : string.Format("{0}|{1}", 2, -1);
                    }
                }
                else
                {
                    retVal = string.Format("{0}|{1}", 2, -1);
                }

                StaticResetSessionVaribles(currentSession);

                #endregion
            }

            return(retVal.ToString());
        }