101个LINQ例子(4)

Console.WriteLine(\ foreach (var n in commonNumbers) { Console.WriteLine(n); } }

Intersect - 2

publicvoid Linq51() {

List products = GetProductList(); List customers = GetCustomerList();

var productFirstChars = from p in products select p.ProductName[0]; var customerFirstChars = from c in customers

select c.CompanyName[0];

var commonFirstChars = productFirstChars.Intersect(customerFirstChars);

Console.WriteLine(\ foreach (var ch in commonFirstChars) { Console.WriteLine(ch); } }

Except - 1

public void Linq52() {

int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 }; int[] numbersB = { 1, 3, 5, 7, 8 };

IEnumerable aOnlyNumbers = numbersA.Except(numbersB); Console.WriteLine(\ foreach (var n in aOnlyNumbers) { Console.WriteLine(n); } }

Except - 2

public void Linq53() {

List products = GetProductList(); List customers = GetCustomerList(); var productFirstChars = from p in products

select p.ProductName[0]; var customerFirstChars =

from c in customers

select c.CompanyName[0];

var productOnlyFirstChars = productFirstChars.Except(customerFirstChars);

Console.WriteLine(\ foreach (var ch in productOnlyFirstChars) { Console.WriteLine(ch); } }

Conversion Operators To Array

public void Linq54() {

double[] doubles = { 1.7, 2.3, 1.9, 4.1, 2.9 }; var sortedDoubles = from d in doubles orderby d descending

select d;

var doublesArray = sortedDoubles.ToArray();

Console.WriteLine(\ for (int d = 0; d < doublesArray.Length; d += 2) { Console.WriteLine(doublesArray[d]); } }

To List

public void Linq55() {

string[] words = { \ var sortedWords = from w in words orderby w

select w;

var wordList = sortedWords.ToList(); Console.WriteLine(\ foreach (var w in wordList) { Console.WriteLine(w); } }

To Dictionary

public void Linq56() {

var scoreRecords = new [] { new {Name = \ new {Name = \ new {Name = \ };

var scoreRecordsDict = scoreRecords.ToDictionary(sr => sr.Name); Console.WriteLine(\}

OfType

public void Linq57() {

object[] numbers = { null, 1.0, \ var doubles = numbers.OfType();

Console.WriteLine(\ foreach (var d in doubles) { Console.WriteLine(d); } }

Element Operators First - Simple

public void Linq58() {

List products = GetProductList(); Product product12 = ( from p in products

where p.ProductID == 12 select p ) .First();

ObjectDumper.Write(product12); }

First - Indexed

public void Linq60() {

int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

int evenNum = numbers.First((num, index) => (num % 2 == 0) && (index % 2 == 0)); Console.WriteLine(\ }

FirstOrDefault - Simple public void Linq61() { int[] numbers = {};

int firstNumOrDefault = numbers.FirstOrDefault(); Console.WriteLine(firstNumOrDefault); }

FirstOrDefault - Condition

public void Linq62() {

List products = GetProductList();

Product product789 = products.FirstOrDefault(p => p.ProductID == 789);

Console.WriteLine(\ }

FirstOrDefault - Indexed public void Linq63() {

double?[] doubles = { 1.7, 2.3, 4.1, 1.9, 2.9 };

double? num = doubles.FirstOrDefault((n, index) => (n >= index - 0.5 && n <= index + 0.5)); if (num != null)

Console.WriteLine(\ else

Console.WriteLine(\ }

ElementAt

public void Linq64() {

int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 }; int fourthLowNum = ( from n in numbers where n < 5

select n )

.ElementAt(3); // 3 because sequences use 0-based indexing Console.WriteLine(\ }

Generation Operators Range

public void Linq65() {

var numbers =

from n in Sequence.Range(100, 50)

selectnew {Number = n, OddEven = n % 2 == 1 ? \ foreach (var n in numbers) {

Console.WriteLine(\ } }

Repeat

public void Linq66() {

var numbers = Sequence.Repeat(7, 10); foreach (var n in numbers) { Console.WriteLine(n); } }

Quantifiers

Any - Simple

public void Linq67() {

string[] words = { \ bool iAfterE = words.Any(w => w.Contains(\

Console.WriteLine(\ }

Any - Indexed

public void Linq68() {

int[] numbers = { -9, -4, -8, -3, -5, -2, -1, -6, -7 };

bool negativeMatch = numbers.Any((n, index) => n == -index);

Console.WriteLine(\ }

Any - Grouped

public void Linq69() {

List products = GetProductList(); var productGroups = from p in products

group p by p.Category into g

where g.Group.Any(p => p.UnitsInStock == 0) select new {Category = g.Key, Products = g.Group}; ObjectDumper.Write(productGroups, 1); }

All - Simple

public void Linq70() {

int[] numbers = { 1, 11, 3, 19, 41, 65, 19 }; bool onlyOdd = numbers.All(n => n % 2 == 1);

Console.WriteLine(\ }

All - Indexed

public void Linq71() {

int[] lowNumbers = { 1, 11, 3, 19, 41, 65, 19 }; int[] highNumbers = { 7, 19, 42, 22, 45, 79, 24 };

bool allLower = lowNumbers.All((num, index) => num < highNumbers[index]);

Console.WriteLine(\{0}\ }

All - Grouped

public void Linq72() {

List products = GetProductList();