DataTable 更改在有数据列的类型方法

 /// <summary>         /// 修改数据表DataTable某一列的类型和记录值(正确步骤：1.克隆表结构，2.修改列类型，3.修改记录值，4.返回希望的结果)         /// </summary>         /// <param name="argDataTable">数据表DataTable</param>         /// <returns>数据表DataTable</returns>  

 private DataTable UpdateDataTable(DataTable argDataTable)         {             DataTable dtResult = new DataTable();             //克隆表结构             dtResult = argDataTable.Clone();             foreach (DataColumn col in dtResult.Columns)             {                 if (col.ColumnName == "RQ")                 {                     //修改列类型                     col.DataType = typeof(String);                 }             }             foreach (DataRow row in argDataTable.Rows)             {                 DataRow rowNew = dtResult.NewRow();                 rowNew["DTBM"] = row["DTBM"];                 //修改记录值                 rowNew["RQ"] = Convert.ToDateTime(row["RQ"]).ToString("yyyy-MM-dd").ToString();                 rowNew["DWBM"] = row["DWBM"];                 rowNew["DWMC"] = row["DWMC"];                 rowNew["YYID"] = row["YYID"];                 rowNew["YYMC"] = row["YYMC"];                 rowNew["YXCL"] = row["YXCL"];                 dtResult.Rows.Add(rowNew);             }             return dtResult;         }