Linq DataTable的修改和查询

迷南。 2022-01-05 02:22 277阅读 0赞

using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Web; 
using System.Web.UI; 
using System.Web.UI.WebControls; 
using System.Data; 
namespace WebApplication\_study.Linq 
\{ 
public partial class LinqStart : System.Web.UI.Page 
\{ 
protected void Page\_Load(object sender, EventArgs e) 
\{ 
DataTable dt = getDataTable.getData();//源数据 
//Linq进行普通查询 
var q1 = from dt1 in dt.AsEnumerable()//查询 
orderby dt1.Field<int>("ID") descending//排序 
where dt1.Field<int>("ID") > 2 && dt1.Field<int>("ID") < 6//条件 
select dt1; 
Response.Write("查询结果为： "); 
foreach (var item in q1)//显示查询结果 
\{ 
//Response.Write(" " + item.Field<string>("Name"));//两种写法均可 
Response.Write(" " + item\["Name"\]); 
\} 
//查询结果用于新的DT 
DataTable newDT = q1.CopyToDataTable<DataRow>();//经查询生成的DT可用于数据绑定 
Response.Write(" 新的DT的结果为： "); 
foreach (var item2 in newDT.AsEnumerable())//显示查询结果 
\{ 
Response.Write(" " + item2\["Name"\]); 
\} 
// 修改查询的结果 
Response.Write(" 修改查询结果前： "); 
var q3 = from dt3 in dt.AsEnumerable() 
select dt3; 
foreach (var item in q3) 
\{ 
Response.Write(" " + item\["ID"\] + "&nbsp;&nbsp;&nbsp;" + item\["Name"\] + "&nbsp;&nbsp;&nbsp;" + item\["PID"\] + "&nbsp;&nbsp;&nbsp;"); 
\} 
Response.Write(" 修改查询结果后： "); 
foreach (var items in dt.AsEnumerable()) 
\{ 
int PID = (int)items\["PID"\]; 
items.SetField<int>("PID", PID + 100); 
\} 
foreach (var item in q3) 
\{ 
Response.Write(" " + item\["ID"\] + "&nbsp;&nbsp;&nbsp;" + item\["Name"\] + "&nbsp;&nbsp;&nbsp;" + item\["PID"\] + "&nbsp;&nbsp;&nbsp;"); 
\} 
//DataView测试 
DataView dvDT = dt.AsDataView(); 
EnumerableRowCollection<DataRow> quert4 = from dv in dt.AsEnumerable() select dv; 
DataView dvDTQ = quert4.AsDataView(); 
 
//linq调用本地方法 
//定义本地方法 
Response.Write(" linq调用本地方法： "); 
int\[\] num = \{ 1, 2, 3, 4, 5, 6, 7, 8, 9 \}; 
var query = from i in num where check(i) select i; 
foreach (var item in query) 
\{ 
Response.Write(item + " "); 
\} 
\} 
/// <summary> 
/// 本地方法示例 
/// </summary> 
/// <param name="num"></param> 
/// <returns></returns> 
public bool check(int num) 
\{ 
if (num > 5) 
return true; 
else 
return false; 
\} 
\} 
\}

转载于:https://www.cnblogs.com/sunxf2011/archive/2011/07/08/2101008.html