步步为营-24-委托

委托:将函数作为参数传递 

例如:操作将一个字符串数组转化为一下大写,小写,转变和打印,普通方法这么写

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

namespace Delegate
{
    class Program
    {
       public static void Main(string[] args)
        {
           //定义字符串
            string[] str = {"Abc","Def","GhIJk"};

            MakeChange(str);
            Show(str);
            GetUpper(str);
            Show(str);
            GetLower(str);
            Show(str);
            Console.Read();
        }

       public static void GetUpper(string[] strs) 
       {
           for (int i = 0; i < strs.Length; i++)
           {
               strs[i] = strs[i].ToString().ToUpper();
           } 
       }

       public static void GetLower(string[] strs) 
       {
           for (int i = 0; i < strs.Length; i++)
           {
               strs[i] =  strs[i].ToString().ToLower();
           } 
       }

       public static void MakeChange(string[] strs) 
       {
           for (int i = 0; i < strs.Length; i++)
           {
               strs[i] = "//"+strs[i]+"\\\\";
           }        
       }

       public static void Show(string[] strs) 
       {
           foreach (var item in strs)
           {
               Console.WriteLine(item);
           }
       }
    }
}

这是我们可以使用委托进行改变,我们观察到所有的方法参数和返回值的类型都是一样的.可以声明一个委托

Delegate string del(string [] strs);

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

namespace Delegate
{
  
    //声明委托
    public delegate string del(string str);
    class Program
    {
       public static void Main(string[] args)
        {
           //定义字符串
            string[] strs = {"Abc","Def","GhIJk"}; 
           //定义委托-法一
            del mc= new del(GetUpper);
            MakeChange(strs , mc);
           //定义委托 -法二
            mc = GetLower;
            MakeChange(strs,mc);

            mc = GetChange;
            MakeChange(strs, mc);
           Console.Read();
        }

       public static void MakeChange(string[] strs,del Method) 
       {
           for (int i = 0; i < strs.Length; i++)
           {
            strs[i] =  Method(strs[i]);
            Console.WriteLine(strs[i]);
           } 
       }

       public static string GetUpper(string strs)
       {
           return strs.ToString().ToUpper();
       }

       public static string GetLower(string strs)
       {
           return strs.ToString().ToLower();
       }

       public static string GetChange(string strs)
       {
           return "//"+strs.ToString()+"\\\\";
       }
    }
}

可能会觉得委托并没带来多大简洁,可以通过匿名委托

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

namespace Delegate
{
  
    //声明委托
    public delegate string del(string str);
    class Program
    {
       public static void Main(string[] args)
        {
           //定义字符串
            string[] strs = {"Abc","Def","GhIJk"};
            del getUpper = delegate(string str) { return str.ToUpper(); };
            MakeChange(strs,getUpper);
            del getLower = delegate(string str) { return str.ToLower(); };
            MakeChange(strs, getLower);
            del getChange = delegate(string str) { return "//"+str+"\\\\"; };
            MakeChange(strs, getChange);
           Console.Read();
        }

       public static void MakeChange(string[] strs,del Method) 
       {
           for (int i = 0; i < strs.Length; i++)
           {
            strs[i] =  Method(strs[i]);
            Console.WriteLine(strs[i]);
           } 
       }

      
    }
}

那么通过lmadab表达式呢?

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

namespace Delegate
{
  
    //声明委托
    public delegate string del(string str);
    class Program
    {
       public static void Main(string[] args)
        {
           //定义字符串
            string[] strs = {"Abc","Def","GhIJk"};
            del getUpper = (str) => { return str.ToUpper(); };
            MakeChange(strs,getUpper);
            del getLower = (str) => { return str.ToLower(); };
            MakeChange(strs, getLower);
            del getChange = (str) => { return "\\\\"+str+"//"; };
            MakeChange(strs, getChange);
           Console.Read();
        }

       public static void MakeChange(string[] strs,del Method) 
       {
           for (int i = 0; i < strs.Length; i++)
           {
            strs[i] =  Method(strs[i]);
            Console.WriteLine(strs[i]);
           } 
       }

      
    }
}

总结
del getUpper = delegate(string str) { return str.ToUpper(); };

del getUpper = (str) { return str.ToUpper(); };