摘自MSDN ：https://msdn.microsoft.com/zh-cn/library/bb549151(v=vs.100).aspx
1.平时定义一个委托
using System;
//声明委托
delegate string ConvertMethod(string inString); public class DelegateExample
{
public static void Main()
{
// 用UppercaseString 方法实例化委托
ConvertMethod convertMeth = UppercaseString;
string name = "Dakota";
// 调用委托
Console.WriteLine(convertMeth(name));
} private static string UppercaseString(string inputString)
{
return inputString.ToUpper();
}
}
2. 泛型委托 Func<T,TResult> 出场
备注: 还有个Action<T> 泛型委托, 和 Func<T,TResult> 的区别是前者没有返回值, 后者必须返回值
Action<T> : https://msdn.microsoft.com/zh-cn/library/018hxwa8(v=vs.100).aspx
Func<T,TResult> : https://msdn.microsoft.com/zh-cn/library/bb549151(v=vs.100).aspx
using System; public class GenericFunc
{
public static void Main()
{
// 注意Func<string,string>,直接就声明了委托,不像刚才那么麻烦
Func<string, string> convertMethod = UppercaseString;
string name = "Dakota";
// 调用委托
Console.WriteLine(convertMethod(name));
} private static string UppercaseString(string inputString)
{
return inputString.ToUpper();
}
}
3.配合 匿名函数(这里用的lambda) 出场,一行代码搞定!!!
using System; public class LambdaExpression
{
public static void Main()
{
//一行代码搞定!!! 左泛型委托,右函数实现
Func<string, string> convert = s => s.ToUpper(); string name = "Dakota";
//调用委托
Console.WriteLine(convert(name));
}
}
4. 应用哈,将一个数组内的字母,全部转成大写
using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq; static class Func
{
static void Main(string[] args)
{
//一行代码,左泛型委托,右实现
Func<string, string> selector = str => str.ToUpper(); // 创建数组.
string[] words = { "orange", "apple", "Article", "elephant" };
// 将委托传入数组Select方法,实现转成大写
IEnumerable<String> aWords = words.Select(selector); // 打印数组成员
foreach (String word in aWords)
Console.WriteLine(word);
}
}
/*
最后输出: ORANGE
APPLE
ARTICLE
ELEPHANT
*/