Csharp/CSharp Tutorial/LINQ/foreach loop
Содержание
Cars going faster than 55, ordered by PetName
<source lang="csharp">using System; using System.Collections.Generic; using System.Text; using System.Xml.Linq; using System.Linq;
class Car
{
public string PetName;
public string Color;
public int Speed;
public string Make;
public override string ToString()
{
return string.Format("Make={0}, Color={1}, Speed={2}, PetName={3}",Make, Color, Speed, PetName);
}
}
class Program
{
static void Main(string[] args)
{
Car[] myCars = new []{
new Car{ PetName = "A", Color = "Silver", Speed = 100, Make = "BMW"},
new Car{ PetName = "B", Color = "Black", Speed = 55, Make = "VW"},
new Car{ PetName = "C", Color = "White", Speed = 43, Make = "Ford"}
};
var subset = from c in myCars where c.Speed > 55 orderby c.PetName descending select c;
foreach (Car c in subset)
{
Console.WriteLine(c.ToString());
}
}
}</source>
Linq over array
<source lang="csharp">using System; using System.Collections.Generic; using System.Text; using System.Xml.Linq; using System.Linq;
class Program
{
static void Main(string[] args)
{
int[] numbers = { 10, 20, 30, 40, 1, 2, 3, 8 };
var subset = from i in numbers where i < 10 select i;
foreach (var i in subset)
Console.Write("Item: {0} ", i);
Console.WriteLine("resultSet is of type: {0}", subset.GetType().Name);
Console.WriteLine("resultSet location: {0}", subset.GetType().Assembly);
}
}</source>
Linq Over ArrayList
<source lang="csharp">using System; using System.Collections.Generic; using System.Text; using System.Xml.Linq; using System.Linq; using System.Collections;
class Car
{
public string PetName;
public string Color;
public int Speed;
public string Make;
}
class Program
{
static void Main(string[] args)
{
ArrayList myCars = new ArrayList();
myCars.Add(new Car{ PetName = "Henry", Color = "Silver", Speed = 100, Make = "BMW"});
myCars.Add(new Car{ PetName = "Clunker", Color = "Rust", Speed = 5, Make = "Yugo"});
myCars.Add(new Car { PetName = "Melvin", Color = "White", Speed = 43, Make = "Ford" });
IEnumerable<Car> myCarsEnum = myCars.OfType<Car>();
// Create a query expression.
var fastCars = from c in myCarsEnum where c.Speed > 55 select c;
foreach (var car in fastCars)
{
Console.WriteLine("{0} is going too fast!", car.PetName);
}
}
}</source>
Linq Over Array Using Sequence
<source lang="csharp">using System; using System.Collections.Generic; using System.Text; using System.Xml.Linq; using System.Linq;
class Program
{
static void Main(string[] args)
{
string[] currentVideoGames = {"test", "this is a test", "asdf", "game 1","game 2", "game 3"};
var subset = from g in currentVideoGames where g.Length > 6 orderby g select g;
foreach (var s in subset)
Console.WriteLine("Item: {0}", s);
}
}</source>
Linq To Objects
<source lang="csharp">using System; using System.Text; using System.Linq; using System.Collections.Generic;
class LinqToObjects
{
static void Main(string[] args)
{
string[] names = { "test", "test 1", "Am" };
IEnumerable<string> namesOfPeople = from name in names where name.Length <= 2 select name;
foreach (var name in namesOfPeople)
Console.WriteLine(name);
}
}</source>
Simple linq
<source lang="csharp">using System; using System.Collections.Generic; using System.Linq; using System.Text;
public class Customer
{
public string FirstName { get; set; }
public string LastName { get; set; }
public string EmailAddress { get; set; }
public override string ToString()
{
return string.Format("{0} {1}\nEmail: {2}",FirstName, LastName, EmailAddress);
}
}
public class Tester
{
static void Main()
{
List<Customer> customers = new List<Customer>{
new Customer { FirstName = "A",
LastName = "B",
EmailAddress = "o@a.ru"},
new Customer { FirstName = "B",
LastName = "C",
EmailAddress = "k@a.ru" },
new Customer { FirstName = "D",
LastName = "C",
EmailAddress = "d@a.ru" },
new Customer { FirstName = "F",
LastName = "G",
EmailAddress = "j@a.ru" },
new Customer { FirstName = "L",
LastName = "H",
EmailAddress = "l@a.ru" }
};
IEnumerable<Customer> result =
from customer in customers
where customer.FirstName == "Donna"
select customer;
foreach (Customer customer in result)
Console.WriteLine(customer.ToString());
customers[3].FirstName = "Donna";
foreach (Customer customer in result)
Console.WriteLine(customer.ToString());
}
}</source>
Use foreach loop to deal with the result from linq
<source lang="csharp">using System; using System.Collections.Generic; using System.Linq; using System.Text; public class MainClass {
public static void Main() {
List<Customer> customers = GetCustomerList();
var waCustomers =
from c in customers
where c.Region == "R1"
select c;
foreach (var customer in waCustomers) {
Console.WriteLine("Customer {0}: {1}", customer.CustomerId, customer.rupanyName);
foreach (var order in customer.Orders) {
Console.WriteLine(" Order {0}: {1}", order.Id, order.OrderDate);
}
}
}
static List<Customer> GetCustomerList() {
List<Product> empTree = new List<Product>();
empTree.Add(new Product { ProductName = "A", Category = "O", UnitPrice = 12, UnitsInStock = 5, Total = 36, OrderDate = new DateTime(2005, 1, 1), Id = 1 });
empTree.Add(new Product { ProductName = "B", Category = "O", UnitPrice = 2, UnitsInStock = 4, Total = 35, OrderDate = new DateTime(2005, 1, 1), Id = 1 });
empTree.Add(new Product { ProductName = "C", Category = "O", UnitPrice = 112, UnitsInStock = 3, Total = 34, OrderDate = new DateTime(2005, 1, 1), Id = 1 });
empTree.Add(new Product { ProductName = "D", Category = "O", UnitPrice = 112, UnitsInStock = 0, Total = 33, OrderDate = new DateTime(2005, 1, 1), Id = 1 });
empTree.Add(new Product { ProductName = "E", Category = "O", UnitPrice = 1112, UnitsInStock = 2, Total = 32, OrderDate = new DateTime(2005, 1, 1), Id = 1 });
empTree.Add(new Product { ProductName = "F", Category = "O", UnitPrice = 11112, UnitsInStock = 0, Total = 31, OrderDate = new DateTime(2005, 1, 1), Id = 1 });
List<Customer> l = new List<Customer>();
l.Add(new Customer { CompanyName = "A", Region = "R1", UnitsInStock = 1, Orders = empTree, CustomerId =0});
l.Add(new Customer { CompanyName = "B", Region = "R2", UnitsInStock = 2, Orders = empTree, CustomerId = 1 });
l.Add(new Customer { CompanyName = "C", Region = "R3", UnitsInStock = 3, Orders = empTree, CustomerId = 2 });
l.Add(new Customer { CompanyName = "D", Region = "R4", UnitsInStock = 4, Orders = empTree, CustomerId = 3 });
l.Add(new Customer { CompanyName = "E", Region = "R5", UnitsInStock = 5, Orders = empTree, CustomerId = 4 });
return l;
}
} class Customer : IComparable<Customer> {
public string CompanyName { get; set; }
public string Region { get; set; }
public List<Product> Orders { get; set; }
public int UnitsInStock { get; set; }
public int CustomerId { get; set; }
public override string ToString() {
return String.Format("Id: {0}, Name: {1}, Region: {3}", this.CustomerId, this.rupanyName, this.Region);
}
int IComparable<Customer>.rupareTo(Customer other) {
if (other == null)
return 1;
if (this.CustomerId > other.CustomerId)
return 1;
if (this.CustomerId < other.CustomerId)
return -1;
return 0;
}
} class Product : IComparable<Product> {
public string ProductName { get; set; }
public string Category { get; set; }
public int UnitPrice { get; set; }
public int UnitsInStock { get; set; }
public int Total { get; set; }
public DateTime OrderDate { get; set; }
public int Id { get; set; }
public override string ToString() {
return String.Format("Id: {0}, Name: {1} , Category: {3}", this.Id, this.ProductName, this.Category);
}
int IComparable<Product>.rupareTo(Product other) {
if (other == null)
return 1;
if (this.Id > other.Id)
return 1;
if (this.Id < other.Id)
return -1;
return 0;
}
}</source>
