GridView無數據時，顯示表頭

   DataTable dtTmp
    {
        get
        {
            if (ViewState["dtTmp"] == null)
            {
                return null;
            }
            return ViewState["dtTmp"] as DataTable;
        }
        set
        {
            ViewState["dtTmp"] = value;
        }
    }

  private void GridBind()
    {

 　　//BLL層調用DAL層 function（）
        dtTmp = NoPayManager.AccessObject.SlctDate();
        GridNoPay.DataSource = dtTmp;
        GridNoPay.DataBind();
    }

 #region 產生GirdView空白表頭

    protected void GridNoPay_PreRender(object sender, EventArgs e)
    {
        if (dtTmp != null)
        {
            if (dtTmp.Rows.Count == 0 || this.GridNoPay.Rows.Count == 0)
            {
                renderEmptyGridView(this.GridNoPay, DAL.NoPayDao.GetRenderEmptyGridViewColumnNames(this.dtTmp));
            }
        }
    }
    /// <summary>
    /// 產生空白表頭
    /// </summary>
    /// <param name="GridView"></param>
    /// <param name="ColumnNames"></param>1
    public static void renderEmptyGridView(GridView GridView, string ColumnNames)
    {
        try
        {
            DataTable dt = new DataTable();

            char[] separator = { ',' };

            string[] columnNames = ColumnNames.Split(separator);

            #region "   空白表頭"

            //GridView無資料時，新增DataColumn
            foreach (string columnName in columnNames)
            {
                DataColumn dataColumn = new DataColumn(columnName.Trim());
                dt.Columns.Add(dataColumn);
            }

            //GridView無資料時，新增DataRow
            DataRow DataRow = dt.NewRow();
            foreach (string columnName in columnNames)
            {
                DataRow[columnName.Trim()] = System.DBNull.Value;
            }
            dt.Rows.Add(DataRow);

            #endregion

            GridView.DataSourceID = null;

            GridView.DataSource = dt;

            GridView.DataBind();

            GridView.Rows[0].Visible = false;
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }
    #endregion

//DAL:

  public static readonly NoPayDao AccessObject = new NoPayDao();
        //  string SqlCon = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
        public static string GetRenderEmptyGridViewColumnNames(DataTable DT)
        {
            try
            {
                string data = string.Empty;
                for (int i = 0; i < DT.Columns.Count; i++)
                {
                    data += (i == 0 ? string.Empty : ",");
                    data += DT.Columns[i].ColumnName;
                }
                return data;
            }
            catch (Exception ex)
            {
                throw ex;
            }
        }
        public DataTable SlctDate()
        {
            string sql = @"select  t.leaveid, t.leavename, t.status, to_char(t.starttime,'yyyy/mm/dd') starttime, to_char(t.endtime,'yyyy/mm/dd') endtime, t.updateby,t.updatetime
                             from  lookup t ORDER BY  t.leaveid";
            try
            {
                // DataSet ds = new DataSet();
                DataSet ds = OracleHelper.Query(sql, "Pay");
                //if (ds != null && ds.Tables.Count > 0 && ds.Tables[0] != null && ds.Tables[0].Rows.Count > 0)
                //{
                      return ds.Tables[0];
                //}
                //else
                //{
                //    return null;
                //}
            }
            catch
            {
                throw new Exception();
            }
        }