C# 委托

委托学习要点:

1.为什么要使用委托

将一个方法作为参数传递给另一个方法.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace 为什么使用委托
{

    public delegate void DelProStr(string [] names);
    public delegate string DelProStr2(string name);

    class Program
    {
        static void Main(string[] args)
        {
            //三个需求
            //1.将一个字符串数组中每个元素都转换成大写
            //2.将一个字符串数组中每个元素都转换成小写
            //3.将一个字符串数组中每个元素两边都加上 双引号

            string[] names = { "abCDefG", "HIJKlmnOP", "QRsTuW", "XyZ" };

            //Test(names, ProStrToUpper);

            //ProStr(names, ToSYH);

            //匿名函数
            ProStr(names, delegate(string name) {
                return name.ToLower();
            });

            for (int i = 0; i < names.Length; i++)
            {
                Console.WriteLine(names[i]);
            }
            Console.ReadKey();
        }

        #region
        public static void ProStr(string [] names,DelProStr2 del2)
        {
            for(int i=0;i<names.Length;i++)
            {
                names[i] = del2(names[i]);
            }
        }

        public static string ToUpper(string name)
        {
            return name.ToUpper();
        }

        public static string Tolower(string name)
        {
            return name.ToLower();
        }

        public static string ToSYH(string name)
        {
            return """+name+""";
        }

        #endregion

        public static void Test(string [] names,DelProStr del)
        {
            del(names);
        }

        //大写
        public static void ProStrToUpper(string[] names)
        {
            for (int i = 0; i < names.Length; i++)
            {
                names[i] = names[i].ToUpper();
            }
        }

        //小写
        public static void ProStrToLower(string [] names)
        {
            for(int i=0;i<names.Length;i++)
            {
                names[i] = names[i].ToLower();
            }
        }

        //双引号
        public static void ProStrSYH(string [] names)
        {
            for(int i=0;i<names.Length;i++)
            {
                names[i] = """ + names[i] + """;
            }
        }


    }
}

2.委托的概念

声明一个委托类型

委托所指向的函数必须跟委托具有相同的签名(参数和返回值)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace _08委托概念
{
    //声明一个委托指向一个函数
    public delegate void DelSayHi(string name);

    class Program
    {
        static void Main(string[] args)
        {
            //DelSayHi del = new DelSayHi(SayChinese);
            DelSayHi del = SayChinese;
            //Test("张三",);
            Test("张三", SayChinese);
            Test("alexx", SayEnglish);


            Console.ReadKey();
        }

        public static void Test(string name,DelSayHi del)
        {
            //调用
            del(name);
        }

        public static void SayChinese(string name)
        {
            Console.WriteLine("吃了么?"+name);
        }

        public static void SayEnglish(string name)
        {
            Console.WriteLine("Nice to meet you"+name);
        }

    }
}

3.匿名函数

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace _09匿名函数
{
    public delegate void DelSay(string name);
    class Program
    {
        static void Main(string[] args)
        {
            //匿名函数
            DelSay del = delegate(string name) {
                Console.WriteLine("Hello"+name);
            };
            del("alexx");
            

            //lamda表达式 => goes to
            DelSay del = (string name) => { Console.WriteLine("HI "+name); };
            del("alexx");

            Console.ReadKey();
        }

        //public static void 
    }
}

4.练习:使用委托求数组的最大值

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace _10求数组的最大值
{
    public delegate int DelCompare(object o1,object o2);
    class Program
    {
        static void Main(string[] args)
        {
            object [] o ={"1","2","3","4","56"};
            //DelCompare del = Compare;
            //object resule = GetMax(o, Compare2);
            object result = GetMax(o, delegate(object o1, object o2)
            {
                string s1 = (string)o1;
                string s2 = (string)o2;
                return s1.Length - s2.Length;
            });

            Console.WriteLine(result);
            Console.ReadKey();

        }

        public static object GetMax(object [] nums,DelCompare del)
        {
            object max = nums[0];
            for(int i=0;i<nums.Length;i++)
            {
                if(del(max,nums[i]) < 0)
                {
                    max =nums[i];
                }
            }
            return max;

        }

        public static int Compare(object o1,object o2)
        {
            int n1 = (int)o1;
            int n2 = (int)o2;
            return n1 - n2;
        }

        public static int  Compare2(object o1,object o2)
        {
            string s1 = (string)o1;
            string s2 = (string)o2;
            return s1.Length - s2.Length;
        }

        //int数组
        public static int GetMax(int [] nums)
        {
            int max = nums[0];
            for(int i=0;i<nums.Length;i++)
            {
                if (max < nums[i])
                    max = nums[i];
            }
            return max;
        }

        //string数组
        public static string GetMax(string [] names)
        {
            string max = names[0];
            for(int i=0;i<names.Length;i++)
            {
                if (max.Length < names[i].Length)
                    max = names[i];
            }
            return max;
        }

    }
}

5.练习:使用委托求任意数组的最大值 =>泛型委托

6.泛型委托

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace _11泛型委托
{
    public delegate int DelCompare<T>(T o1, T o2);
    class Program
    {
        static void Main(string[] args)
        {
            int [] nums = {1,2,3,4,5,123 };
            int max = GetMax<int>(nums, delegate(int o1, int o2) {
                return o1 - o2;
            });
            Console.WriteLine(max);
            Console.ReadKey();

        }

        public static T GetMax<T>(T[] nums, DelCompare<T> del)
        {
            T max = nums[0];
            for (int i = 0; i < nums.Length; i++)
            {
                if (del(max, nums[i]) < 0)
                {
                    max = nums[i];
                }
            }
            return max;

        }
    }
}

7.多播委托

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace 多播委托
{
    public delegate void DelTest(string str);
    class Program
    {
        static void Main(string[] args)
        {
            //
            DelTest del = t1;
            del += t2;
            del += t3;
            del("aa");

            Console.WriteLine(del);

            Console.ReadLine();
        }

        private static void t1(string name)
        {
            Console.WriteLine("t1"+name);
        }

        private static void t2(string name)
        {
            Console.WriteLine("t2"+name);
        }

        private static void t3(string name)
        {
            Console.WriteLine("t3"+name);
        }

    }
}

8.lamda表达式

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace _12lamda表达式
{
    public delegate void Delone();
    public delegate void Deltwo(string name);
    public delegate string Delthree(string name);
    class Program
    {
        static void Main(string[] args)
        {
            Delone one = delegate() { };
            Delone two = () => { };

            Deltwo a = delegate(string name) { };
            Deltwo b = (string name) => { };

            Delthree ac = delegate(string name) { return name; };
            Delthree ab =(string name)=>{return name;};

            List<int> list = new List<int>() { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
            list.RemoveAll(n => n >= 8);//lamda表达式
            foreach(var item in list)
            {
                Console.WriteLine(item);
            }

            Console.ReadKey();

        }


    }
}

9.使用委托来实现窗体传值.

(父窗体与子窗体来回传值)

FORM1：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            Form2 frm2 = new Form2();
            frm2.dellaber = laberShow;
            frm2.Show();
            //this.Hide();
        }

        private void laberShow(string str)
        {
            this.label1.Text = str;
        }

        private void button2_Click(object sender, EventArgs e)
        {
            Form2 frm2 = new Form2();
            frm2.Textbox1 = this.label1.Text + "ZQ!";
            frm2.Show();
        }
    }
}

FORM2：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    public delegate void DelShowForm1Laber(string str);
    public partial class Form2 : Form
    {
        public DelShowForm1Laber dellaber;
        public Form2()
        {
            InitializeComponent();
        }
        private string _textbox1;

        public string Textbox1
        {
            get { return _textbox1; }
            set { _textbox1 = value;
            this.label1.Text = _textbox1;
            }
        }

        private void button1_Click(object sender, EventArgs e)
        {
            this.textBox1.Text = this.textBox1.Text.Trim();
            //fuzhi
         
            //Form1 frm1 = new Form1();
            //frm1.Show();
            dellaber(this.textBox1.Text);

            this.Hide();
        }

        private void form2_laber(string str)
        {
            this.label1.Text = str;
        }
    }
}