【C#】在datatable中添加一序號列，編號從1依次遞增，並且在第一列

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/// <summary>
        /// 在DataTable中添加一序號列，編號從1依次遞增
        /// </summary>
        /// <param >DataTable</param>
        /// <returns></returns>
        private DataTable AddSeriNumToDataTable(DataTable dt)
        {        
            //需要返回的值
            DataTable dtNew;
            if (dt.Columns.IndexOf("序號") >= 0)
            {
                dtNew = dt;
            }
            else //添加一序號列,並且在第一列
            {
                int rowLength = dt.Rows.Count;
                int  colLength= dt.Columns.Count;
                DataRow[] newRows = new DataRow[rowLength];

                dtNew = new DataTable();
                //在第一列添加“序號”列
                dtNew.Columns.Add("序號");
                for (int i = 0; i < colLength; i++)
                {
                    dtNew.Columns.Add(dt.Columns[i].ColumnName);
                    //復制dt中的數據
                    for (int j = 0; j < rowLength; j++)
                    {
                        if (newRows[j] == null)
                            newRows[j] = dtNew.NewRow();
                        //將其他數據填充到第二列之后，因為第一列為新增的序號列
                        newRows[j][i+1] = dt.Rows[j][i];
                    }
                }
                foreach (DataRow row in newRows)
                {
                    dtNew.Rows.Add(row);
                }

            }
            //對序號列填充，從1遞增
            for (int i = 0; i < dt.Rows.Count; i++)
            {
                dtNew.Rows[i]["序號"] = i + 1;
            }

            return dtNew;           
            
        }