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
     
      ("ID") descending//排序                     where dt1.Field
      
       ("ID") > 2 && dt1.Field
       
        ("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
        
         ("Name"));//两种写法均可                Response.Write("
         
" + item["Name"]);            }            //查询结果用于新的DT            DataTable newDT = q1.CopyToDataTable
         
          ();//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"] + "   " + item["Name"] + "   " + item["PID"] + "   ");            }            Response.Write("
          
修改查询结果后：
          
");            foreach (var items in dt.AsEnumerable())            {                int PID = (int)items["PID"];                items.SetField
          
           ("PID", PID + 100); } foreach (var item in q3) { Response.Write("
           
" + item["ID"] + "   " + item["Name"] + "   " + item["PID"] + "   "); } //DataView测试 DataView dvDT = dt.AsDataView(); EnumerableRowCollection
           
             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 + " "); } } /// 
            
 /// 本地方法示例 /// 
 /// 
             /// 
             public bool check(int num) { if (num > 5) return true; else return false; } }}
           
          
         
        
       
      
     

PS:如果出现指定转换无效的异常，说明查询语句里面有问题。一般是Field<T>的泛型有误，应当仔细检查DataTable中列的DataType。

　　然后还可可以这么写

IEnumerable
     
       query =    from order in orders.AsEnumerable()    where order.Field
      
       ("OrderDate") > new DateTime(2001, 8, 1)    select order;// Create a table from the query.DataTable boundTable = query.CopyToDataTable
       
        ();
       
      
     

 

本文转载自：http://www.cnblogs.com/sunxf2011/archive/2011/07/08/2101008.html