DataTable相关操作，筛选，取前N条数据，获取指定列数据

 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
 2         /// <summary>
 3         /// 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
 4         /// eg:SortExprDataTable(dt,"Sex='男'","Time Desc",1)
 5         /// </summary>
 6         /// <param name="dt">传入的DataTable</param>
 7         /// <param name="strExpr">筛选条件</param>
 8         /// <param name="strSort">排序条件</param>
 9         /// <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>
10         public static DataTable SortDataTable(DataTable dt, string strExpr, string strSort, int mode)
11         {
12             switch (mode)
13             {
14                 case 1:
15                     //方法一　直接用DefaultView按条件返回
16                     dt.DefaultView.RowFilter = strExpr;
17                     dt.DefaultView.Sort = strSort;
18                     return dt;
19                 case 2:
20                     //方法二　DataTable筛选，排序返回符合条件行组成的新DataTable
21                     DataTable dt1 = new DataTable();
22                     DataRow[] GetRows = dt.Select(strExpr, strSort);
23                     //复制DataTable dt结构不包含数据
24                     dt1 = dt.Clone();
25                     foreach (DataRow row in GetRows)
26                     {
27                         dt1.Rows.Add(row.ItemArray);
28                     }
29                     return dt1;
30                 default:
31                     return dt;
32             }
33         }
34         #endregion
35         #region 获取DataTable前几条数据
36         /// <summary>
37         /// 获取DataTable前几条数据
38         /// </summary>
39         /// <param name="TopItem">前N条数据</param>
40         /// <param name="oDT">源DataTable</param>
41         /// <returns></returns>
42         public static DataTable DtSelectTop(int TopItem, DataTable oDT)
43         {
44             if (oDT.Rows.Count < TopItem) return oDT;
45 
46             DataTable NewTable = oDT.Clone();
47             DataRow[] rows = oDT.Select("1=1");
48             for (int i = 0; i < TopItem; i++)
49             {
50                 NewTable.ImportRow((DataRow)rows[i]);
51             }
52             return NewTable;
53         }
54         #endregion
55 
56         #region 获取DataTable中指定列的数据
57         /// <summary>
58         /// 获取DataTable中指定列的数据
59         /// </summary>
60         /// <param name="dt">数据源</param>
61         /// <param name="tableName">新的DataTable的名词</param>
62         /// <param name="strColumns">指定的列名集合</param>
63         /// <returns>返回新的DataTable</returns>
64         public static DataTable GetTableColumn(DataTable dt, string tableName, params string[] strColumns)
65         {
66             DataTable dtn = new DataTable();
67             if (dt == null)
68             {
69                 throw new ArgumentNullException("参数dt不能为null");
70             }
71             try
72             {
73                 dtn = dt.DefaultView.ToTable(tableName, true, strColumns);
74             }
75             catch (Exception e)
76             {
77                 throw new Exception(e.Message);
78             }
79             return dtn;
80         }
81         #endregion