委托的定义:
(1) 将方法作为变量使用的一种机制,就是将方法当作变量用(声明，赋值，传参)
(2)
将变量当作方法来用，首先就要去声明变量，就要考虑变量的类型，就是(委托变量，对应方法的返回值，参数等)，顾名思义：委托就是委托别人去干某些事情，下面是一个实例方法的实现
例如：我现在饿了，但是我很懒，就是不想出去买，所以这时候我可以委托室友帮我带一份，这样我就已经实现委托了
class Program
{
//声明一个委托
delegate int DelegateCompare(object o1, object o2);delegate int DelegateTotal(int num1, int num2);
static void Main(string[] args)
{//比较两个整数
DelegateCompare del = intCompare; //简写
Console.WriteLine(del(1, 2));//比较两个字符的长度
del = new DelegateCompare(strLengthCompare); //完整写法
Console.WriteLine(del("123456", "admin"));del = PersonAgeCompare; //简写
Console.WriteLine(del(new Person("张三", 18), new Person("李四", 20)));/*-------------取最大值-----------*/
DelegateCompare delMax;delMax = intCompare; //整数
Console.WriteLine(GetMax(new object[] { 1, 5, 3, 6, 8, 7 }, delMax));delMax = strLengthCompare; //字符串长度
Console.WriteLine(GetMax(new object[] { "aa", "a", "aaa", "aaaa", "aaaaaaaa", "a" }, delMax));delMax = PersonAgeCompare; //Person类的Age属性
Console.WriteLine(((Person)GetMax(new object[] { new Person("张三", 18), new Person("李四", 14), new Person("万物", 20) }, delMax)).Name);/*----------匿名委托----------*/
//标准写法
DelegateCompare del2 = delegate(object o1, object o2) { return (int)o1 - (int)o2; };
Console.WriteLine("匿名委托" + del2(5, 3));
//lambda 表达式
DelegateCompare del3 = (object o1, object o2) => (int)o1 - (int)o2; //del3 同等于Del4
DelegateCompare del4 = (object o1, object o2) => { return (int)o1 - (int)o2; };/*--------系统委托-----------*/
//lambda 表达式
string[] names = { "agen", "balen", "coure", "apple" };
string[] findNameA = Array.FindAll<string>(names, delegate(string v) { return v.StartsWith("a"); });
string[] findNameB = Array.FindAll<string>(names, v => v.StartsWith("a"));
Console.WriteLine(string.Join("-", findNameA));
Console.WriteLine(string.Join("-", findNameB));/*----------------多播委托----------*/
//多播委托一般情况下 要求没有返回值, 若有, 则返回最后一个方法的返回值
DelegateTotal delTotal = He;
delTotal += Cha;
delTotal += Ji;
Console.WriteLine(delTotal(2, 4));
Console.ReadKey();
}/// <summary>
/// 获取array最大值
/// </summary>
/// <param name="arr"></param>
/// <param name="del"></param>
/// <returns></returns>
static object GetMax(object[] arr, DelegateCompare del)
{
if (arr.Length > 1)
{
object _max = arr[0];
for (int i = 1; i < arr.Length; i++)
{
if (del(_max, arr[i]) < 0)
{
_max = arr[i];
}
}
return _max;
}
return null;
}/// <summary>
/// 比较两个Person类的Age属性 大于0 o1大 等于0 相等 小于0 o2大
/// </summary>
/// <param name="o1"></param>
/// <param name="o2"></param>
/// <returns></returns>
static int PersonAgeCompare(object o1, object o2)
{
return ((Person)o1).Age - ((Person)o2).Age;
}/// <summary>
/// 比较两个字符串的长度 大于0 o1大 等于0 相等 小于0 o2大
/// </summary>
/// <param name="o1"></param>
/// <param name="o2"></param>
/// <returns></returns>
static int strLengthCompare(object o1, object o2)
{
return o1.ToString().Length - o2.ToString().Length;
}/// <summary>
/// 比较两个数的大小 大于0 o1大 等于0 相等 小于0 o2大
/// </summary>
/// <param name="o1"></param>
/// <param name="o2"></param>
/// <returns></returns>
static int intCompare(object o1, object o2)
{
return (int)o1 - (int)o2;
}/// <summary>
/// 求和
/// </summary>
/// <param name="num1"></param>
/// <param name="num2"></param>
/// <returns></returns>
static int He(int num1, int num2)
{
Console.WriteLine("----求和----");
return num1 + num2;
}
/// <summary>
/// 求差
/// </summary>
/// <param name="num1"></param>
/// <param name="num2"></param>
/// <returns></returns>
static int Cha(int num1, int num2)
{
Console.WriteLine("----求差----");
return num1 - num2;
}
/// <summary>
/// 求积
/// </summary>
/// <param name="num1"></param>
/// <param name="num2"></param>
/// <returns></returns>
static int Ji(int num1, int num2)
{
Console.WriteLine("----求积----");
return num1 * num2;
}
}//定义一个Person类
class Person
{
//姓名
private string name = "";
//年龄
private int age = 0;
//构造方法
public Person(string PName, int PAge)
{
this.Name = PName;
this.Age = PAge;
}
public int Age
{
get { return age; }
set { age = value; }
}
public string Name
{
get { return name; }
set { name = value; }
}}
C# 委托, 铭轩同学原创