Message:Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding

 private void ValidateExcel()
    {
        DataSet dsError = new BLExcelImport().GetImportValidation();
        if (dsError.Tables.Count > 0)
        {
            if (dsError.Tables[0].Rows[0]["ERROR"].ToString() == "ERROR")
            {
                grdErrorLising.Visible = true;
                BindGrid();
                Session["ShowImportGrid"] = "Yes";
            }
            else
            {
                grdErrorLising.Visible = false;
                ExecuteRatingEngine();
            }
        }
    }

   public DataSet GetImportValidation()
        {
            return (new DAExcelImport().GetImportValidation());
        }

   public DataSet GetImportValidation()
        {
            try
            {
                return SqlHelper.ExecuteDataset(SQLConnectivity.CONN_STRING, CommandType.StoredProcedure, PROC_GETIMPORTVALIDATION);
            }
            catch (Exception oException)
            {
                new Common().SendMailException(oException.Message, this.GetType().Name, "usp_getImportValidation");
                throw oException;
            }
        }

When i upload the excel which contains more than 2000 excel it gives  the exception

"Message:Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding."

How can i increase timeout to the code