其实也是对网上linq--select篇的扩充
我在这里把两种语法都写,lambda,linq写法,方便大家更好的去学习,同时也增加了一些新的东西,如解释,例子的扩充。。。
今后一段时间,我会对linq一些基本写法进行例子和解释结合的方式和大家进行分享。
class Program

{
private static 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;

}

static void Main(string[] args)

{
List<Student> studentList = GetStudents();

Select(studentList);
}

private static void Select<T>(T studentList)

{
OnlySearch(studentList);
SearchCollectChangeOtherCollect(studentList);
BuilderAnomy();
BuilderAnomyExter();
SelectLambda();
ComplexSelect();
ComplexSelectLambda();
}

private static void OnlySearch<T>(T studentList)

{
Console.WriteLine("<hr>只查询合适对象集合的某个属性:<br>");

//lamb的写法
var students = RevealChangeType(studentList).Where(n=>n.Language == "Chinese").Select(n=>n.Name);

//linq的写法
//var students = from n in RevealChangeType(studentList)
// where n.Language == "Chinese"
// select n.Name;

foreach (var student in students)

{
Console.WriteLine(string.Format("<span class='result'>{0}</span>", student));
}
}

private static IEnumerable<Student> RevealChangeType<T>(T obj)

{
IEnumerable<Student> student = obj as IEnumerable<Student>;

return student;
}

private static void SearchCollectChangeOtherCollect<T>(T obj)

{
Console.WriteLine("<hr>从一个集合中查询,转化到另外一个集合:<br>");

//age Array

int[] intArray =
{ 25, 1, 4, 3 };

//lamb的写法
var students = intArray.SelectMany(n=>RevealChangeType(obj).Where(s=>s.Age == n));

//linq的写法
//var students = from s in RevealChangeType(obj)
// from n in intArray
// where s.Age == n
// select s;

foreach (var student in students)

{
Console.WriteLine(string.Format("<span class='result'>{0}</span>", student.Name));
}
}

private static void BuilderAnomy()

{
Console.WriteLine("<hr>构建匿名类型:<br>");

List<Student> studentList = GetStudents();

int[] intArray =
{ 3, 1, 6, 4 };

//lamb的写法

var stu = intArray.Select(n=>new
{ Id = n, Name = (studentList as List<Student>)[n].Name });

//linq的写法
//var stu = from n in intArray
// select new{Id = n,Name=(studentList as List<Student>)[n].Name};

foreach (var s in stu)

{
Console.WriteLine(string.Format("<div class='result'>id:{0};name:{1}</div>", s.Id, s.Name));
}
}

private static void BuilderAnomyExter()

{
Console.WriteLine("<hr>构建匿名类型2——扩展已有类:<br>");

List<Student> studentList = GetStudents();

int[] intArray =
{ 3, 1, 6, 4 };

//lamb的写法

var students = intArray.Select(n=>new
{ Id = n, studentList[n].Name, studentList[n].Age });

//linq的写法
//var students = from n in intArray
// select new {Id = n, studentList[n].Name, studentList[n].Age};

foreach (var student in students)

{
Console.WriteLine(string.Format("<div class='result'>id:{0}; name:{1}; age:{2}</div>", student.Id, student.Name, student.Age));
}
}

private static void SelectLambda()

{
Console.WriteLine("<hr>select的Lambda表达式:<br>");

List<Student> studentList = GetStudents();

int[] intArray =
{ 3, 1, 6, 4 };

//lamb的写法

var stu = intArray.Select(i=>new
{ Id = i, studentList[i].Name });

//linq的写法
//var stu = from i in intArray
// select new {Id = i, studentList[i].Name};

foreach (var student in stu)

{
Console.WriteLine(string.Format("<div class='result'>id:{0}; name:{1}</div>", student.Id, student.Name));
}
}

private static void ComplexSelect()

{
Console.WriteLine("<hr>复合选择:<br>");

List<Student> studentList = GetStudents();

string[] stringArray =
{ "Ajax", "Csharp", "Javascript", "Css Desige", "Asp.net", "Gis" };

//lamb的写法
//var stu = stringArray.Where(s=>s.Length > 8).SelectMany(s=>studentList.Where(str1=>str1.Age > 23).Select(str=>new { book = s, name = str.Name }));

var stu = studentList.Where(sl=>sl.Age > 23).SelectMany(sl=>stringArray.Where(s=>s.Length > 8).Select(s=>new
{ name = sl.Name, book = s }));

//linq的写法
//var stu = from sl in studentList
// where sl.Age > 23
// from s in stringArray
// where s.Length > 8
// select new {name = sl.Name, book = s};

foreach (var student in stu)

{
Console.WriteLine(string.Format("<div class='result'>{0} is studying {1}</div>", student.name, student.book));
}
}

private static void ComplexSelectLambda()

{
Console.WriteLine("<hr>多重选择的Lambda表达式:<br>");

List<Student> studentList = GetStudents();

string[] stringArray =
{ "Ajax", "Csharp", "Javascript", "Css Desige", "Asp.net", "Gis" };

//lamb的写法
//var stu = studentList.SelectMany(s=>stringArray.Select(str => s.Name + "has a book names " + str));

//linq的写法
var stu = from sl in studentList
from s in stringArray

select new
{name=sl.Name,language=s};

foreach (var s in stu)

{
Console.WriteLine(string.Format("<div class='result'>{0}</div>", s));
}
}
}

sealed class Student

{
public int age;
public int Age

{

get
{ return age; }

set
{ age = value; }
}

private string name;
public string Name

{

get
{ return name; }

set
{ name = value; }
}

private string language;
public string Language

{

get
{ return language; }

set
{ language = value; }
}
}
对此方法的补充
ComplexSelectLambda()
**********************************
但是现在(ComplexSelectLambda())输出的结果是:
<hr>多重选择的Lambda表达式:<br/>

<div class='result'>
{name=YOUNG, language=Ajax}</div>

<div class='result'>
{name=YOUNG, language=Csharp}</div>

<div class='result'>
{name=YOUNG, language=Javascript}</div>

<div class='result'>
{name=YOUNG, language=Css Desige}</div>

<div class='result'>
{name=YOUNG, language=Asp.net}</div>

<div class='result'>
{name=YOUNG, language=Gis}</div>
**********************************


/**///////////////////////////////////
问题:如何写才能输入这样的结果?
<name=young,language=Ajax>
<name=JESSIE,language=Csharp>
<name=KELLY,language=Javascript>
<name=JUNE,language=Css Desige>
<name=ADRIAN,language=Asp.net>
<name=BRUCE,language=Gis>

/**///////////////////////////////////

代码:
private static void ComplexSelectLambdaTwo()

{
Console.WriteLine("<hr>多重选择的Lambda表达式:<br>");

List<Student> studentList = GetStudents();

string[] stringArray =
{ "Ajax", "Csharp", "Javascript", "Css Desige", "Asp.net", "Gis" };


var langlist = stringArray.Select(( la, i) => new
{ lang = la, index = i });


var stulist = studentList.Select(( st, i) => new
{ name = st.Name, index = i });

var stu2 = from la in langlist
from st in stulist
where la.index == st.index

select new
{name = st.name, language = la.lang};

foreach (var s2 in stu2)

{
Console.WriteLine(string.Format("<name={0},language={1}>", s2.name, s2.language));
}
}
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