в 15:31, 26 мая 2010

2010-05-26T15:31:18Z

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2010-05-26T11:38:44Z

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==A Query Using the Standard Dot Notation Syntax==

<source lang="csharp">

using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
public class MainClass {
public static void Main() {
string[] names = { "A1", "B123", "C123123", "E", "W" };
IEnumerable<string> sequence = names
.Where(n => n.Length < 6)
.Select(n => n);
foreach (string name in sequence) {
Console.WriteLine("{0}", name);
}
}
}
</source>

==Assign the loop variable to another variable declared inside the statement block==

<source lang="csharp">
using System;
using System.Collections.Generic;
using System.Linq;
public class MainClass {
public static void Main() {
IEnumerable<char> vowels = "aeiou";
IEnumerator<char> rator = vowels.GetEnumerator();
IEnumerable<char> query = "Not what you might expect";

foreach (char vowel in "aeiou") {
char temp = vowel;
query = query.Where(c => c != temp);
}
}
}
</source>

==Filtered: prints the name of each element of an integer array that is less than 5==

<source lang="csharp">
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
public class MainClass {
public static void Main() {
int[] numbers = { 5, 4, 1, 3};
string[] digits = { "zero", "one", "two", "three"};
var lowNums =
from n in numbers
where n < 5
select digits[n];
Console.WriteLine("Numbers < 5:");
foreach (var num in lowNums) {
Console.WriteLine(num);
}
}
}
</source>

==Filter string by its length==

<source lang="csharp">
using System;
using System.Collections.Generic;
using System.Linq;
class LinqDemo {
static void Main() {
string[] names = { "Tom", "Dick", "Harry" };

IEnumerable<string> filteredNames = names.Where(n => n.Length >= 4);
foreach (string name in filteredNames) Console.Write(name + "|");
}
}
</source>

==prints strings where each element has the second letter "i".==

<source lang="csharp">
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
public class MainClass {
public static void Main() {
string[] digits = { "ziro", "one", "two", "three"};
var reversedIDigits = (
from d in digits
where d[1] == "i"
select d)
.Reverse();
foreach (var d in reversedIDigits) {
Console.WriteLine(d);
}
}
}
</source>

==Query string value by String.StartsWith==

<source lang="csharp">
using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
public class MainClass {
public static void Main() {
string[] presidents = {"Ad", "Ar", "Bu", "B", "C", "C"};
string president = presidents.Where(p => p.StartsWith("Ad")).First();
Console.WriteLine(president);
}
}
</source>

==Query Using the Query Expression Syntax==

<source lang="csharp">

using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
public class MainClass {
public static void Main() {
string[] names = { "A123123", "B123", "C123123", "E123", "W" };
IEnumerable<string> sequence = from n in names
where n.Length < 6
select n;
foreach (string name in sequence) {
Console.WriteLine("{0}", name);
}
}
}
</source>

==Query with an Exception==

<source lang="csharp">

using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
public class MainClass {
public static void Main() {
string[] presidents = {"AAAA", "aaaa", "bacDert", "B1234", "Carter"};
IEnumerable<string> items = presidents.Where(s => Char.IsLower(s[4]));
Console.WriteLine("After the query.");
foreach (string item in items)
Console.WriteLine(item);
}
}
</source>

==To remove all vowels from a string.==

<source lang="csharp">
using System;
using System.Collections.Generic;
using System.Linq;
public class MainClass {
public static void Main() {
IEnumerable<char> query = "Not what you might expect";
query = query.Where(c => c != "a");
query = query.Where(c => c != "e");
query = query.Where(c => c != "i");
query = query.Where(c => c != "o");
query = query.Where(c => c != "u");
foreach (char c in query) Console.Write(c);
}
}
</source>

==Two where clauses==

<source lang="csharp">
using System;
using System.Collections;
using System.Collections.Generic;
using System.Text;
using System.Linq;
class Employee {
int _id;
int _idRole;
string _lastName;
string _firstName;
public int ID {
get { return _id; }
set { _id = value; }
}
public int IDRole {
get { return _idRole; }
set { _idRole = value; }
}
public string LastName {
get { return _lastName; }
set { _lastName = value; }
}
public string FirstName {
get { return _firstName; }
set { _firstName = value; }
}
}
class Salary {
int _id;
int _year;
double _salary;
public int ID {
get { return _id; }
set { _id = value; }
}
public int Year {
get { return _year; }
set { _year = value; }
}
public double SalaryPaid {
get { return _salary; }
set { _salary = value; }
}
}
public class MainClass {
public static void Main() {
List<Employee> people = new List<Employee> {
new Employee { ID = 1, IDRole = 1, LastName = "A", FirstName = "B"},
new Employee { ID = 2, IDRole = 2, LastName = "G", FirstName = "T"}
};
List<Salary> salaries = new List<Salary> {
new Salary { ID = 1, Year = 2004, SalaryPaid = 10000.00 },
new Salary { ID = 1, Year = 2005, SalaryPaid = 15000.00 },
new Salary { ID = 1, Year = 2005, SalaryPaid = 15000.00 }
};
IEnumerable<Salary> q = from p in people
where p.ID == 1
from s in salaries
where s.ID == p.ID
select s;

}
}
</source>

==Use && in where clause==

<source lang="csharp">
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
public class MainClass {
public static void Main() {
List<Product> products = GetProductList();
var expensiveInStockProducts =
from p in products
where p.UnitsInStock > 0 && p.UnitPrice > 3.00M
select p;
foreach (var product in expensiveInStockProducts) {
Console.WriteLine(product.ProductName);
}
}
static List<Product> GetProductList() {
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 });
return empTree;
}
}
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>

==Use string method in where clause==

<source lang="csharp">

using System;
using System.Linq;
public class MainClass {
public static void Main() {
string[] greetings = { "hello world", "hello LINQ", "hello" };
var items =
from s in greetings
where s.EndsWith("LINQ")
select s;
foreach (var item in items)
Console.WriteLine(item);
}
}
</source>

==use where clause in a while loop==

<source lang="csharp">
using System;
using System.Collections.Generic;
using System.Linq;
public class MainClass {
public static void Main() {
IEnumerable<char> vowels = "aeiou";
IEnumerator<char> rator = vowels.GetEnumerator();
IEnumerable<char> query = "Not what you might expect";
char vowel;
while (rator.MoveNext()) {
vowel = rator.Current;
query = query.Where(c => c != vowel);
}
}
}
</source>

==Use where to filer object list==

<source lang="csharp">
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
public class MainClass {
public static void Main() {
List<Product> products = GetProductList();
var soldOutProducts =
from p in products
where p.UnitsInStock == 0
select p;
Console.WriteLine("Sold out products:");
foreach (var product in soldOutProducts) {
Console.WriteLine("{0} is sold out!", product.ProductName);
}
}
static List<Product> GetProductList() {
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 });
return empTree;
}
}
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>

==where clause==

<source lang="csharp">
using System;
using System.Collections;
using System.Collections.Generic;
using System.Text;
using System.Linq;
using System.Reflection;
class Person {
int _id;
int _idRole;
string _lastName;
string _firstName;
public int ID {
get { return _id; }
set { _id = value; }
}
public int IDRole {
get { return _idRole; }
set { _idRole = value; }
}
public string LastName {
get { return _lastName; }
set { _lastName = value; }
}
public string FirstName {
get { return _firstName; }
set { _firstName = value; }
}
}
class Program {
static void Main(string[] args) {
List<Person> people = new List<Person> {
new Person { ID = 1, IDRole = 1, LastName = "A", FirstName = "B"},
new Person { ID = 2, IDRole = 2, LastName = "G", FirstName = "T"},
new Person { ID = 3, IDRole = 2, LastName = "G", FirstName = "M"},
new Person { ID = 4, IDRole = 3, LastName = "C", FirstName = "G"}
};
var query = people.Where((p, index) => p.IDRole == index);
}
}
</source>

==Where clause with string method and return IEnumerable object==

<source lang="csharp">
using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
public class MainClass {
public static void Main() {

string[] presidents = {"AA", "A", "AAA", "B", "Ca", "C"};
IEnumerable<string> items = presidents.Where(p => p.StartsWith("A"));
foreach (string item in items)
Console.WriteLine(item);
}
}
</source>

==Where Prototype==

<source lang="csharp">
using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
public class MainClass {
public static void Main() {
string[] presidents = {"A", "Ar", "B", "Bu", "C", "Cleveland"};
IEnumerable<string> sequence = presidents.Where(p => p.StartsWith("C"));
foreach (string s in sequence)
Console.WriteLine("{0}", s);
}
}
</source>

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