using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;namespace FuncTest
{class Program{// 委托声明 -- 定义一个签名:delegate double MathAction(double num);static double Double(double input){return input* 2;}static void Main(string[] args){//***********************普通委托//使用一个方法实例化委托MathAction ma = Double;double result = ma(4.5);Console.WriteLine(result.ToString());//匿名方法MathAction ma2 = delegate(double input) {return input * 3;};Console.WriteLine(ma2(3));//lambda表达式MathAction ma3 = s => s * s * s;Console.WriteLine(ma3(2));//**********************Func<T,Tresult>委托//利用Func，不用再显示定义委托Func<double, double> ma4 = Double;Console.WriteLine(ma4(5).ToString());//利用Func，匿名方法Func<double,double> ma5 = delegate (double input) {return input * input;};Console.WriteLine(ma5(5));//利用Func，lambda表达式Func<double, double> ma6 = s => s * s * s;Console.WriteLine(ma6(5));//和其他表达式结合// 声明了一个Func委托类型的变量selector并用Lambda表达式进行实例化 // 这个Lambda表达式将用来获取一个字符串并将这个字符串转化为大写并返回Func<string, string> selector = str => str.ToUpper();// 创建一个字符串数组string[] words = { "orange", "apple", "Article", "elephant" };// 依次遍历这个字符串数组并调用委托实例selector进行处理IEnumerable<String> aWords = words.Select(selector);// 输出结果到控制台foreach (String word in aWords)Console.WriteLine(word);//**********************Action<T> 委托,与Func<T,TResult>唯一的区别就是没有返回值
Action<string> ma7 = delegate (string input){Console.WriteLine(input);};ma7("from Action<string>");//***********************Predicate<T>, 形式只有一个，传入一个参数，返回一个bool值Predicate<string[]> predicate = delegate (string[] x){var r = from p in xwhere p.Contains("s")select p;if (r.ToList().Count > 0){return true;}else{return false;}};string[] _value = { "charlies", "nancy", "alex", "jimmy", "selina" };if (predicate(_value)){Console.WriteLine("They contain.");}else{Console.WriteLine("They don't contain.");}Console.ReadLine();}}
}