第一个Linq练习
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Xml.Linq;
using System.Xml;
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
第一个例子入门例子
// 1. Data source.
int[] numbers = new int[7] { 0, 1, 2, 3, 4, 5, 6 };
// 2. Query creation.
// numQuery is an IEnumerable<int>
var nums =
from num in numbers
where (num % 2) == 0
select num;
// 3. Query execution.
foreach (int num in nums)
{
Console.Write("{0,1} ", num);
}
Console.Write("{0,1} ", nums.First());
Console.ReadLine();
简单范型结构
int[] numbers = new int[7] { 0, 1, 2, 3, 4, 5, 6 };
List<int> ints =
(from num in numbers
where (num % 2) == 0
select num).ToList();
//var numQuery3 = (from num in numbers where (num % 2) == 0 select num).ToArray();
foreach (int i in ints)
{
Console.WriteLine(i);
}
Console.ReadLine();
对象范型结构
List<employee> employees = new List<employee>();
employees.Add(new employee("张三", 16));
employees.Add(new employee("张四", 17));
employees.Add(new employee("张五", 18));
employees.Add(new employee("张六", 19));
employees.Add(new employee("李四", 16));
employees.Add(new employee("王五", 16));
//另一种写法
//List<employee> customerQuery =
// (from age16 in employees
// where age16.Age == 16
// select age16).ToList();
IEnumerable<employee> customerQuery =
from age16 in employees
where age16.Age == 16
select age16;
foreach (employee mye in customerQuery)
{
Console.WriteLine(mye.Name+mye.Age);
}
Console.ReadLine();
合并的例子
List<Student> students = new List<Student>()
{
new Student { First = "Svetlana", Last = "Omelchenko", ID = 111, Street = "123 Main Street", City = "Seattle", Scores = new List<int> { 97, 92, 81, 60 } },
new Student { First = "Claire", Last = "O’Donnell", ID = 112, Street = "124 Main Street", City = "Seattle", Scores = new List<int> { 75, 84, 91, 39 } },
new Student { First = "Sven", Last = "Mortensen", ID = 113, Street = "125 Main Street", City = "Lake City", Scores = new List<int> { 88, 94, 65, 91 } }, };
// Create the second data source.
List<Teacher> teachers = new List<Teacher>()
{
new Teacher {First="Ann", Last="Beebe", ID=945, City = "Seattle"},
new Teacher {First="Alex", Last="Robinson", ID=956, City = "Redmond"},
new Teacher {First="Michiyo", Last="Sato", ID=972, City = "Tacoma"} };
// Create the query.
var peopleInSeattle =
(from student in students
where student.City == "Seattle"
select new { fn=student.First, ln=student.Last }).Concat(from teacher in teachers
where teacher.City == "Seattle"
select new { fn=teacher.First, ln=teacher.Last });
Console.WriteLine("The following students and teachers live in Seattle:");
// Execute the query.
foreach (var person in peopleInSeattle)
{
Console.WriteLine(person);
}
Console.WriteLine("Press any key to exit.");
Console.ReadKey();
元素操作
Data source.
double[] radii = { 1, 2, 3 };
Query.
IEnumerable<string> query =
from rad in radii
select String.Format("Area = {0}", (rad * rad) * 3.14);
Query execution.
foreach (string s in query)
Console.WriteLine(s);
Keep the console open in debug mode.
Console.WriteLine("Press any key to exit.");
Console.ReadKey();
对象toXML
// Create the data source by using a collection initializer.
List<Student> students = new List<Student>()
{
new Student {First="Svetlana", Last="Omelchenko", ID=111, Scores = new List<int>{97, 92, 81, 60}},
new Student {First="Claire", Last="O’Donnell", ID=112, Scores = new List<int>{75, 84, 91, 39}},
new Student {First="Sven", Last="Mortensen", ID=113, Scores = new List<int>{88, 94, 65, 91}},
};
// Create the query.
var studentsToXML = new XElement("Root",
from student in students
let x = String.Format("{0},{1},{2},{3}", student.Scores[0],student.Scores[1],student.Scores[2], student.Scores[3])
select new XElement("student",
new XElement("First", student.First),
new XElement("Last", student.Last),
new XElement("Scores", x)
)
// end "student"
);
// end "Root"
// Execute the query.
Console.WriteLine(studentsToXML);
// Keep the console open in debug mode.
Console.WriteLine("Press any key to exit.");
Console.ReadKey();
}
}
public class employee
{
public string Name
{
get;
set;
}
public int Age
{
get;
set;
}
public employee(string name,int age)
{
Name = name;
Age = age;
}
}
class Student
{
public string First { get; set; }
public string Last { get; set; }
public int ID { get; set; }
public string Street { get; set; }
public string City { get; set; }
public List<int> Scores;}
class Teacher
{
public string First { get; set; }
public string Last { get; set; }
public int ID { get; set; }
public string City { get; set; }
}
}