Linq学习笔记(1.1)——where

最新推荐文章于 2025-11-25 08:50:12 发布

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#linq #books #class #webform #string #lambda

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本文通过示例展示了LINQ中where关键字的基本使用方法，包括如何根据条件筛选数组和集合体中的元素。同时介绍了where查询的Lambda表达式写法。

(我注：下文是一个linq关键字where的一些用法，源代码里面都有详细的注释说明，大家有兴趣的话，可以试下在新创建的WebForm项目的Default.aspx.cs文件里面粘贴如下代码，看看是不是出来结果的那个图）

using System; using System.Data; using System.Configuration; using System.Linq; using System.Web; using System.Web.Security; using System.Web.UI; using System.Text; using System.Web.UI.WebControls; using System.Web.UI.WebControls.WebParts; using System.Web.UI.HtmlControls; using System.Collections.Generic; using System.Collections; public partial class _Default : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { //根据条件查询数组#region 根据条件查询数组 Response.Write("<hr>列出数组中字符长度大于等于6的字符串数组： "); string[] Demo1 = { "Ajax", "Csharp", "Javascript", "Css Desige", "Asp.net", "Gis" }; var books = from n in Demo1 where n.Length >= 6 select n; foreach (var book in books){ Response.Write(string.Format("{0}", book)); } // where查询的Lambda表达式#region where查询的Lambda表达式 Response.Write("<hr>where查询的快捷方法： "); var books2 = Demo1.Where(book => book.Length >= 6); foreach (var book in books2) { Response.Write(string.Format("{0}", book)); } //根据条件查询集合体#region 根据条件查询集合体 Response.Write("<hr>列出集合中语言为Chinese的学生： "); List<Student> Demo2 = GetStudents(); var students1 = from n in Demo2 where n.Language == "Chinese" select n.Name; foreach (var student in students1){ Response.Write(string.Format("{0}", student)); } //根据条件查询集合体#region 根据条件查询集合体 Response.Write("<hr>列出集合中年龄大于等于20的英国或苏格兰学生： "); var students2 = from n in Demo2 where (n.Language == "English" || n.Language == "Scotland") && n.Age >= 20 select n; foreach (var student in students2){ Response.Write(string.Format("{0}", student.Name)); } } //构造一个学生集合体#region 构造一个学生集合体 private List<Student> GetStudents() { List<Student> students = new List<Student> { new Student{ Name="YOUNG", Age=25, Language="Chinese"}, new Student{ Name="JESSIE", Age=21, Language="Scotland"}, new Student{ Name="KELLY", Age=18, Language="English"}, new Student{ Name="JUNE", Age=20, Language="English"}, new Student{ Name="ADRIAN", Age=22, Language="Italy"}, new Student{ Name="BRUCE", Age=17, Language="Scotland"}, new Student{ Name="BRANT", Age=30, Language="Germany"}, new Student{ Name="BEN", Age=25, Language="Chinese"} }; return students; } } //学生类#region 学生类 class Student { public int Age { get; set; } public string Name { get; set; } public string Language { get; set; } }

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