в 15:31, 26 мая 2010

2010-05-26T15:31:53Z

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2010-05-26T12:18:17Z

1 версия

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==A lambda expression can reference the local variables and parameters of the method in which it"s defined.==

<source lang="csharp">using System;
delegate int NumericSequence();
class Test {
static void Main() {
int seed = 0;
NumericSequence natural = () => seed++;
Console.WriteLine(natural());
Console.WriteLine(natural());
}
}</source>

==A lambda expression has the following BNF form: (parameters) => expression-or-statement-block==

<source lang="csharp">using System;
class Test {
static void Main() {
Func<int, int> square = x => x * x;
Console.WriteLine(square(3)); // 9
}
}</source>

==A local variable instantiated within a lambda expression is unique per invocation of the delegate instance.==

<source lang="csharp">using System;
delegate int NumericSequence();
class Test {
static NumericSequence Natural() {
return () => { int seed = 0; return seed++; };
}
static void Main() {
NumericSequence natural = Natural();
Console.WriteLine(natural());
Console.WriteLine(natural());
}
}</source>

==Concise Lambda Expression==

<source lang="csharp">using System;
using System.ruponentModel;
class MainClass
{
static void Main()
{
Func<string, int> returnLength;
returnLength = (text => text.Length);
Console.WriteLine(returnLength("Hello"));
}
}</source>

==If your query"s lambda expressions reference local variables, these variables are subject to outer variable semantics.==

<source lang="csharp">using System;
using System.Collections.Generic;
using System.Linq;
public class MainClass {
public static void Main() {
int[] numbers = { 1, 2 };
int factor = 10;
IEnumerable<int> query = numbers.Select(n => n * factor);
factor = 20;
foreach (int n in query) Console.Write(n + "|");
}
}</source>

==Lambda expression used to declare a delegate==

<source lang="csharp">using System;
using System.Linq;
using System.Linq.Expressions;
class Program {
static void Main(string[] args) {
Func<int, bool> isOddDelegate = i => (i & 1) == 1;
for (int i = 0; i < 10; i++) {
if (isOddDelegate(i))
Console.WriteLine(i + " is odd");
else
Console.WriteLine(i + " is even");
}
}
}</source>

==Lambda expression used to declare an expression tree==

<source lang="csharp">using System;
using System.Linq;
using System.Linq.Expressions;
class Program {
static void Main(string[] args) {
Expression<Func<int, bool>> isOddExpression = i => (i & 1) == 1;
ParameterExpression param = Expression.Parameter(typeof(int), "i");
Expression<Func<int, bool>> isOdd =
Expression.Lambda<Func<int, bool>>(
Expression.Equal(
Expression.And(
param,
Expression.Constant(1, typeof(int))),
Expression.Constant(1, typeof(int))),
new ParameterExpression[] { param });
Func<int, bool> isOddCompiledExpression = isOddExpression.rupile();
for (int i = 0; i < 10; i++) {
if (isOddCompiledExpression(i))
Console.WriteLine(i + " is odd");
else
Console.WriteLine(i + " is even");
}
}
}</source>

==List Sort With Lambda Expression==

<source lang="csharp">using System.Text;
using System.Xml.Linq;
using System;
using System.Collections.Generic;
using System.ruponentModel;
using System.Linq;
class Product
{
public string Name { get; private set; }
public decimal Price { get; private set; }
public Product(string name, decimal price)
{
Name = name;
Price = price;
}
Product()
{
}
public static List<Product> GetSampleProducts()
{
return new List<Product>
{
new Product { Name="C", Price = 9.99m },
new Product { Name="A", Price=14.99m },
new Product { Name="F", Price=13.99m },
new Product { Name="S", Price=10.99m}
};
}
public override string ToString()
{
return string.Format("{0}: {1}", Name, Price);
}
}
class ListSortWithLambdaExpression
{
static void Main()
{
List<Product> products = Product.GetSampleProducts();
products.Sort(
(first, second) => first.Name.rupareTo(second.Name)
);
foreach (Product product in products)
{
Console.WriteLine(product);
}
}
}</source>

==return a lambda function==

<source lang="csharp">using System;
delegate int NumericSequence();
class Test {
static NumericSequence Natural() {
int seed = 0;
return () => seed++;
}
static void Main() {
NumericSequence natural = Natural();
Console.WriteLine(natural());
Console.WriteLine(natural());
}
}</source>

==square is assigned the lambda expression x = > x * x:==

<source lang="csharp">using System;
delegate int Transformer(int i);
class Test {
static void Main() {
Transformer square = x => x * x;
Console.WriteLine(square(3)); // 9
}
}</source>

==Using Lambda Expressions with Find method==

<source lang="csharp">using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Linq.Expressions;
using System.Xml.Linq;
class Program
{
static void Main(string[] args)
{
//
List<string> myList2 = new List<string>();
myList2.Add("A");
myList2.Add("B");
myList2.Add("C");
myList2.Add("D");
string vanilla2 = myList2.Find((string icecreamname) => icecreamname.Equals("B"));
Console.WriteLine(vanilla2);
}

}</source>

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в 15:31, 26 мая 2010

Admin: 1 версия