101个LINQ例子(2)

SelectMany - Multiple from

public void Linq18() {

List customers = GetCustomerList();

DateTime cutoffDate = new DateTime(1997, 1, 1); var orders =

from c in customers where c.Region == \ from o in c.Orders

where o.OrderDate >= cutoffDate select new {c.CustomerID, o.OrderID}; ObjectDumper.Write(orders); }

SelectMany - Indexed

public void Linq19() {

List customers = GetCustomerList(); var customerOrders =

customers.SelectMany( (cust, custIndex) =>

cust.Orders.Select(o => \

\ ObjectDumper.Write(customerOrders); }

Partitioning Operators Take - Simple

public void Linq20() {

int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 }; var first3Numbers = numbers.Take(3); Console.WriteLine(\ foreach (var n in first3Numbers) { Console.WriteLine(n); } }

Take - Nested public void Linq21() {

List customers = GetCustomerList(); var first3WAOrders = ( from c in customers from o in c.Orders

where c.Region == \

select new {c.CustomerID, o.OrderID, o.OrderDate} ) .Take(3);

Console.WriteLine(\ foreach (var order in first3WAOrders) { ObjectDumper.Write(order); } }

Skip - Simple

public void Linq22() {

int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 }; var allButFirst4Numbers = numbers.Skip(4); Console.WriteLine(\ foreach (var n in allButFirst4Numbers) { Console.WriteLine(n); } }

Skip - Nested

public void Linq23() {

List customers = GetCustomerList(); var waOrders =

from c in customers

from o in c.Orders

where c.Region == \

select new {c.CustomerID, o.OrderID, o.OrderDate}; var allButFirst2Orders = waOrders.Skip(2); Console.WriteLine(\ foreach (var order in allButFirst2Orders) { ObjectDumper.Write(order); } }

TakeWhile - Simple

public void Linq24() {

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

var firstNumbersLessThan6 = numbers.TakeWhile(n => n < 6); Console.WriteLine(\ foreach (var n in firstNumbersLessThan6) { Console.WriteLine(n); } }

SkipWhile - Simple public void Linq26() {

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

var allButFirst3Numbers = numbers.SkipWhile(n => n % 3 != 0);

Console.WriteLine(\ foreach (var n in allButFirst3Numbers) { Console.WriteLine(n); } }

SkipWhile - Indexed public void Linq27() {

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

var laterNumbers = numbers.SkipWhile((n, index) => n >= index);

Console.WriteLine(\elements starting from first element less than position:\

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

Ordering Operators OrderBy - Simple 1 publicvoid Linq28() {

string[] words = { \

var sortedWords = from w in words orderby w select w;

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

OrderBy - Simple 2 public void Linq29() {

string[] words = { \ var sortedWords = from w in words orderby w.Length select w;

Console.WriteLine(\ foreach (var w in sortedWords) { Console.WriteLine(w);

its }

}

OrderBy - Simple 3 public void Linq30() {

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

orderby p.ProductName select p;

ObjectDumper.Write(sortedProducts); }

OrderBy - Comparer

public class CaseInsensitiveComparer : IComparer {

public int Compare(string x, string y) {

return string.Compare(x, y, true); } }

public void Linq31() {

string[] words = { \ var sortedWords = words.OrderBy(a => a, new CaseInsensitiveComparer()); ObjectDumper.Write(sortedWords); }

OrderByDescending - Simple 1 public void Linq32() {

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

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

OrderByDescending - Simple 2 public void Linq33() {

List products = GetProductList(); var sortedProducts =

from p in products

orderby p.UnitsInStock descending select p;

ObjectDumper.Write(sortedProducts); }

OrderByDescending - Comparer

public class CaseInsensitiveComparer : IComparerspan class=\{

publicint Compare(string x, string y) {

returnstring.Compare(x, y, true); } }

publicvoid Linq34() {

string[] words = { \

var sortedWords = words.OrderByDescending(a => a, new CaseInsensitiveComparer());

ObjectDumper.Write(sortedWords); }

ThenBy - Simple publicvoid Linq35() {

string[] digits = { \

var sortedDigits = from d in digits orderby d.Length, d select d;

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

ThenBy - Comparer

public class CaseInsensitiveComparer : IComparerspan class=\{

publicint Compare(string x, string y) {

returnstring.Compare(x, y, true);