筛选datatable数据

1. #region DataTable筛选，排序返回符合条件行组成的新DataTable或直接用DefaultView按条件返回  
   /// <summary>  
   /// DataTable筛选，排序返回符合条件行组成的新DataTable或直接用DefaultView按条件返回  
   /// eg:SortExprDataTable(dt,"Sex='男'","Time Desc",1)  
   /// </summary>  
   /// <param name="dt">传入的DataTable</param>  
   /// <param name="strExpr">筛选条件</param>  
   /// <param name="strSort">排序条件</param>  
   /// <param name="mode">1,直接用DefaultView按条件返回,效率较高;2,DataTable筛选，排序返回符合条件行组成的新DataTable</param>  
   public static DataTable SortDataTable(DataTable dt, string strExpr, string strSort, int mode)  
   {  
       switch (mode)  
       {  
           case 1:  
               //方法一　直接用DefaultView按条件返回  
               dt.DefaultView.RowFilter = strExpr;  
               dt.DefaultView.Sort = strSort;  
               return dt;  
           case 2:  
               //方法二　DataTable筛选，排序返回符合条件行组成的新DataTable  
               DataTable dt1 = new DataTable();  
               DataRow[] GetRows = dt.Select(strExpr, strSort);  
               //复制DataTable dt结构不包含数据  
               dt1 = dt.Clone();  
               foreach (DataRow row in GetRows)  
               {  
                   dt1.Rows.Add(row.ItemArray);  
               }  
               return dt1;  
           default:  
               return dt;  
       }  
   }  
   #endregion  #region 获取DataTable前几条数据  
   /// <summary>  
   /// 获取DataTable前几条数据  
   /// </summary>  
   /// <param name="TopItem">前N条数据</param>  
   /// <param name="oDT">源DataTable</param>  
   /// <returns></returns>  
   public static DataTable DtSelectTop(int TopItem, DataTable oDT)  
   {  
       if (oDT.Rows.Count < TopItem) return oDT;  
     
       DataTable NewTable = oDT.Clone();  
       DataRow[] rows = oDT.Select("1=1");  
       for (int i = 0; i < TopItem; i++)  
       {  
           NewTable.ImportRow((DataRow)rows[i]);  
       }  
       return NewTable;  
   }  
   #endregion  
    
   #region 获取DataTable中指定列的数据  
   /// <summary>  
   /// 获取DataTable中指定列的数据  
   /// </summary>  
   /// <param name="dt">数据源</param>  
   /// <param name="tableName">新的DataTable的名词</param>  
   /// <param name="strColumns">指定的列名集合</param>  
   /// <returns>返回新的DataTable</returns>  
   public static DataTable GetTableColumn(DataTable dt, string tableName, params string[] strColumns)  
   {  
       DataTable dtn = new DataTable();  
       if (dt == null)  
       {  
           throw new ArgumentNullException("参数dt不能为null");  
       }  
       try  
       {  
           dtn = dt.DefaultView.ToTable(tableName, true, strColumns);  
       }  
       catch (Exception e)  
       {  
           throw new Exception(e.Message);  
       }  
       return dtn;  
   }  
   #endregion