C# 3.0 Orcas 简介 (转)
文章来源：http://idior.cnblogs.com/archive/2005/09/14/237089.html
Implicitly typed local variables
var i = 5 ;var s = " Hello " ;var d = 1.0 ;
var numbers = new int [] 
{1, 2, 3} ;var orders = new Dictionary < int ,Order > (); 局部变量的声明变得非常方便, 编译器会根据上下文自动推导出变量的类型.这个功能在3.0中被广泛使用.
局部变量的声明变得非常方便 , 编译器会根据上下文自动推导出变量的类型 . 这个功能在 3.0 中被广泛使用 .下面的代码更加方便 :
var sum = 0 ;var intArray = new [] { 1,2,3,4} ; // used to be new int[](1,2,3,4) foreach ( var i in intArray ) {
sum += i;
}
在匿名类型的支持下,你甚至可以这样玩.
var contacts = new [] {
new {Name = "idior",Website= new[] { "idior.cnblogs.com", "www.alphatom.com" }
},new {Name = "dudu",PhoneNumbers = new[] { "www.aopdotnet.com" }}} ;
可见3.0下的代码是多么的简洁.
var contacts = new [] {new {Name = "idior",Website= new[] { "idior.cnblogs.com", "www.alphatom.com" }},new {Name = "dudu",PhoneNumbers = new[] { "www.aopdotnet.com" }}} ;
可见3.0下的代码是多么的简洁.
var contacts = new [] {new {Name = "idior",Website= new[] { "idior.cnblogs.com", "www.alphatom.com" }},new {Name = "dudu",PhoneNumbers = new[] { "www.aopdotnet.com" }}} ;
可见3.0下的代码是多么的简洁.
Extension methods
在2.0的集合一文中, 我对新List
比如我想为所有的集合类加入Foreach的方法.
24 class Static Algorithm
25 {
26 public static void ForEach
27 {
28 foreach (T obj in collection)
29 {
30 action(obj);
31 }
32 }
33
34 public static void ForSpecification
35 {
36 foreach (T obj in collection)
37 {
38 if (filter(obj))
39 action(obj);
40 }
41 }
42 }
来看看如何使用:
var numbers = new [] {“hello”, “world”, “Orcas”} ;numbers.ForEach ( delegate ( string str) // 相当于Algorithm.ForEach(numbers,…) { Console.WriteLine(str); } ); Extension methods名副其实, 确实为功能扩展带来了极大的方便.
var numbers = new [] {“hello”, “world”, “Orcas”} ;numbers.ForEach ( delegate ( string str) // 相当于Algorithm.ForEach(numbers,…) { Console.WriteLine(str); } ); Extension methods名副其实, 确实为功能扩展带来了极大的方便.
: var numbers = new [] {“hello”, “world”, “Orcas”} ;numbers.ForEach ( delegate ( string str) // 相当于Algorithm.ForEach(numbers,…) { Console.WriteLine(str); } ); Extension methods名副其实, 确实为功能扩展带来了极大的方便.
名副其实, 确实为功能扩展带来了极大的方便.Lambda Expressions
如果说你现在还没有习惯使用匿名方法, 没关系,一年后你将会在你的代码中到处用到它, 而Lambda Expressions则是对匿名方法的进一步增强, 两年后它将充斥我们的代码.
如果你看了我在CollectionClosureMethod in .Net 一文中利用匿名方法对Martin Fowler的CollectionClosureMethod in Ruby的模拟, 但是觉得很丑陋的话, 那么请你看看下面的代码:
21 managers = employees.select {|e| e.manager?} //ruby
22
23 List
24 {
25 return e.IsManager == true;
26 }); //C# 2.0
27
28 var managers = employees.Select(e => e.IsManager==true); //C# 3.0
21 offices = employees.collect {|e| e.office}
22
23 List
24 {
25 return e.Office;
26 });
27
28 var offices = employees.Select(e => e.Office);
Object and Collection initializers
21 managers = employees.select {|e| e.manager?} //ruby
22
23 List
24 {
25 return e.IsManager == true;
26 }); //C# 2.0
27
28 var managers = employees.Select(e => e.IsManager==true); //C# 3.0
21 offices = employees.collect {|e| e.office}
22
23 List
24 {
25 return e.Office;
26 });
27
28 var offices = employees.Select(e => e.Office);
Object and Collection initializers
21 managers = employees.select {|e| e.manager?} //ruby
22
23 List
24 {
25 return e.IsManager == true;
26 }); //C# 2.0
27
28 var managers = employees.Select(e => e.IsManager==true); //C# 3.0
21 offices = employees.collect {|e| e.office}
22
23 List
24 {
25 return e.Office;
26 });
27
28 var offices = employees.Select(e => e.Office);
Object and Collection initializers
对象的初始化的代码将变得异常简洁.
var idior = new Person {Name = "ning", Surname = "xu"} ;var persons = new List < Person > { new Person{Name = "ning", Surname = "xu"}, new Person{Name = "Foo", Surname = "Bar"}}
Anonymous types
var idior = new Person {Name = "ning", Surname = "xu"} ;var persons = new List < Person > { new Person{Name = "ning", Surname = "xu"}, new Person{Name = "Foo", Surname = "Bar"}}
Anonymous types
var idior = new Person {Name = "ning", Surname = "xu"} ;var persons = new List < Person > { new Person{Name = "ning", Surname = "xu"}, new Person{Name = "Foo", Surname = "Bar"}}
Anonymous types
var idior = new {Name = "idior", WebSite = http://idior.cnblogs.com/};Console.WriteLine(idior.WebSite);
Query Expressions
Query Expressions
将关系型查询语句引入面向对象的世界, 大大增强了语法安全性, 很久以前我也对此有过介绍..
from c in customerswhere c.City == " London " select c 相应的Lambda表达式描述
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