multiple file upload in entity framework !

Question

i have a code which accepts multiple file on gridview but when clickd on save it is taking only 1 file

 

protected void btnUpload_Click(object sender, EventArgs e)
   {
       try
       {
           ddlBillType_DataBound(ddlBillType, e);


           DataTable dtDoc = new DataTable();


           if (dtDoc.Rows.Count < 0)
           {


               dtDoc = objTrnFVCBillAction.GetBlankDocumentListDataTable();
               ViewState["dtAddDoc"] = dtDoc;
               lblAutoDocID.Text = "0";

           }
           else
           {
               dtDoc = (DataTable)ViewState["dtAddDoc"];

           }


           if (ddlDocumentName.SelectedValue != "0" && fuSupDocs.FileName != "")
           {
               DataRow dr = dtDoc.NewRow();


               btnUpload.EnableViewState = true;

               if (btnUpload.Text == "Add Document")
               {
                   if (lblAutoDocID.Text == "")
                   {
                       lblAutoDocID.Text = "0";
                   }

                   lblAutoDocID.Text = (long.Parse(lblAutoDocID.Text) + 1).ToString();

                   dr[Constant.Auto_Gen_ID] = long.Parse(lblAutoDocID.Text);
               }
               dr["Document_Name"] = ddlDocumentName.SelectedItem.Text;

               if (fuSupDocs.HasFile)
               {

                       dr["Document_Name"] = fuSupDocs.PostedFile.FileName;

                       string sFileName = string.Empty;


                       sFileName = Server.MapPath(@"~/Temp/" + fuSupDocs.FileName);
                       fuSupDocs.SaveAs(sFileName);

                       dr["Document_URL"] = sFileName;

               }
               if (btnUpload.Text == "Add Document")
               {

                   dtDoc.Rows.Add(dr);
                   ViewState["dtAddDoc"] = dtDoc;

                   grdSuppDocs.DataSource = dtDoc;
                   grdSuppDocs.DataBind();
                   BlankDoc();
               }
           }
       }
       catch (Exception ex)
       {
           Omb.ShowMessage(ex.Message, true);
       }
   }

action page code

 

public DataTable GetBlankDocumentListDataTable()
     {
         DataTable dtDocVoucher = new DataTable();
         dtDocVoucher.Columns.Add(Constant.Auto_Gen_ID, System.Type.GetType("System.Int64"));
         dtDocVoucher.Columns.Add("Document_Name", Type.GetType("System.String"));
         dtDocVoucher.Columns.Add("Document_URL", Type.GetType("System.String"));

         return dtDocVoucher;
     }