Linq学习笔记(1.2)——select

 

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) { //格式化化查询结果格式化化查询结果 Response.Write("<hr>格式化化查询结果：<br>"); string[] stringArray = { "Ajax", "Csharp", "Javascript", "Css Desige", "Asp.net", "Gis" }; var books = from n in stringArray where n.Length >= 6 select "I'm studying " + n; foreach (var book in books){ Response.Write(string.Format("<div class='result'>{0}</div>", book)); } //只查询合适对象集合的某个属性 Response.Write("<hr>只查询合适对象集合的某个属性：<br>"); List<Student> StudentList = GetStudents(); var students1 = from n in StudentList where n.Language == "Chinese" select n.Name; foreach (var student in students1) { Response.Write(string.Format("<span class='result'>{0}</span>", student)); } //从一个集合中查询，转化到另外一个集合 Response.Write("<hr>从一个集合中查询，转化到另外一个集合：<br>"); int[] intArray = { 3, 1, 6, 4 }; var students2 = from n in intArray select StudentList[n]; foreach (var student in students2) { Response.Write(string.Format("<span class='result'>{0}</span>", student.Name)); } //构建匿名类型 Response.Write("<hr>构建匿名类型：<br>"); var stu = from n in intArray select new { Id = n, Name = StudentList[n].Name }; foreach (var s in stu) { Response.Write(string.Format("<div class='result'>id:{0}; name:{1}</div>", s.Id,s.Name)); } //构建匿名类型2——扩展已有类 Response.Write("<hr>构建匿名类型2——扩展已有类：<br>"); var students3 = from n in intArray select new { Id = n, StudentList[n].Name, StudentList[n].Age }; foreach (var student in students3) { Response.Write(string.Format("<div class='result'>id:{0}; name:{1}; age:{2}</div>", student.Id, student.Name, student.Age)); } //select的Lambda表达式 Response.Write("<hr>select的Lambda表达式：<br>"); var students4 = intArray.Select(i => new { Id = i, StudentList[i].Name }); foreach (var student in students4) { Response.Write(string.Format("<div class='result'>id:{0}; name:{1}</div>", student.Id, student.Name)); } // 复合选择 Response.Write("<hr>复合选择：<br>"); var study4 = from a in StudentList where a.Age>23 from b in stringArray where b.Length>8 select new {name=a.Name,book=b}; foreach (var student in study4) { Response.Write(string.Format("<div class='result'>{0} is studying {1}</div>", student.name, student.book)); } //多重选择 Response.Write("<hr>多重选择：<br>"); var study = from a in StudentList where a.Age > 20 from b in stringArray where b.Length > 5 select new {a.Name,book=b}; foreach (var s in study) { Response.Write(string.Format("<div class='result'>name:{0}; book:{1}</div>", s.Name, s.book)); } //多重选择的Lambda表达式 Response.Write("<hr>多重选择的Lambda表达式：<br>"); var study1 = StudentList.SelectMany(student => stringArray.Select(str => student.Name + " has a book names " + str)); foreach (var s in study1) { Response.Write(string.Format("<div class='result'>{0}</div>", s)); } } //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 class Student { public int Age { get; set; } public string Name { get; set; } public string Language { get; set; } }

 

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转自：http://www.cnblogs.com/young18/archive/2007/06/05/772127.html