理解Lambda表达式和闭包

了解由函数指针到Lambda表达式的演化过程

Lambda表达式的这种简洁的语法并不是什么古老的秘法,因为它并不难以理解(难以理解的代码只有一个目的,那就是吓唬程序员)

 1 #include "stdafx.h"
 2 using namespace System;
 3
 4 typedef void(*FunctionPointer)(System::String ^str);
 5
 6 void HelloWorld(System::String ^str)
 7 {
 8     Console::WriteLine(str);
 9     Console::ReadLine();
10 }
11
12 int main(array<System::String ^> ^args)
13 {
14     FunctionPointer fp = HelloWorld;
15     fp("Hello World");
16     return 0;
17 }

函数指针

 1 using System;
 2 using System.Collections.Generic;
 3 using System.Text;
 4
 5 namespace CharpFunctionPointer {
 6     class Program {
 7
 8         delegate void FunctionPointer(string str);
 9
10         static void Main(string[] args) {
11             FunctionPointer fp = HelloWorld;
12             fp("Hello World!");
13         }
14
15         static void HelloWorld(string str) {
16             Console.WriteLine(str);
17             Console.ReadLine();
18         }
19     }
20
21 }

委托

 1 using System;
 2 using System.Collections.Generic;
 3 using System.Text;
 4
 5 namespace CharpFunctionPointer {
 6     class Program {
 7
 8         delegate void FunctionPointer(string str);
 9
10         static void Main(string[] args) {
11             FunctionPointer fp = delegate (string s) {
12                 Console.WriteLine(s);
13                 Console.ReadLine();
14             };
15             fp("Hello World!");
16         }
17     }
18
19 }

匿名委托

 1 using System;
 2 using System.Collections.Generic;
 3 using System.Text;
 4
 5 namespace CharpFunctionPointer {
 6     class Program {
 7
 8         delegate void FunctionPointer(string str);
 9
10         static void Main(string[] args) {
11             FunctionPointer fp =
12                 s => Console.WriteLine(s);
13
14             fp("Hello World!");
15             Console.ReadLine();
16         }
17     }
18 }

Lambda表达式

 1 using System;
 2 using System.Collections.Generic;
 3 using System.Text;
 4
 5 namespace CharpFunctionPointer {
 6     class Program {
 7
 8         static void Main(string[] args) {
 9             Action<string> fp = s => Console.WriteLine(s);
10
11             fp("Hello World!");
12             Console.ReadLine();
13         }
14     }
15 }

将Lambda表达式赋值给一个预定义的泛型委托