C#使用LINQ中Enumerable类方法的延迟与立即执行的控制

程序结果显而易见，所以没有写输出语句；
3.ToDictionary把序列转换为泛型Dictionary<TKey,TValue>

4.ToLookup用于将序列转换为泛型Lookup<TKey,TValue>

Dictionary和Lookup是非常近似的一对类型，都通过“键”访问相关的元素，不同的是Dictionary的Key和Value是一一对应关系，Lookup的Key和Value是一对多关系，Lookup没有公共构造函数，时能用ToLookup构建，创建后也不能删除Lookup中的元素。

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

namespace ToDictionary
{
  /// <summary>
  /// 3.ToDictionary把序列转换为泛型Dictionary<TKey,TValue>
  /// </summary>
  class Program
  {
    static void Main(string[] args)
    {
      List<GuestInfo> gList = new List<GuestInfo>() 
      {
        new GuestInfo(){Name="Jeffrey", Age=33,Tel="136********"},
        new GuestInfo(){ Name="DebugLZQ", Age=25,Tel="187********"},
        new GuestInfo(){Name="Sarah", Age=24,Tel="159********"},
        new GuestInfo(){Name="Jerry", Age=33,Tel="135********"},
        new GuestInfo(){Name="Smith", Age=33,Tel="139********"}        
      };
      //ToDictionary把序列转换为泛型Dictionary
      //ToDictionary重载了4个方法
      //a.用Name作为Dictionary的“键”,guest为“value”
      Dictionary<string, GuestInfo> dictionary1 = gList.ToDictionary(guest => guest.Name);
      foreach (var s in dictionary1 )
      {
        Console.WriteLine("键值{0}:{1} {2} {3}",s.Key,s.Value.Name,s.Value.Age,s.Value.Tel );
      }
      Console.WriteLine("--------------------------------");
      Console.ReadKey();
      //b.自定义比较器      
      Dictionary<string,GuestInfo> dictionary2=gList.ToDictionary(guest=>guest.Name,new MyEqualityComparer<string>());
      foreach (var s in dictionary2)
      {
        Console.WriteLine("键值{0}:{1} {2} {3}", s.Key, s.Value.Name, s.Value.Age, s.Value.Tel);
      }
      Console.WriteLine("--------------------------------");
      Console.ReadKey();
      //c.用Name作为Dictionary的“键”,Tel属性为"value"
      Dictionary<string, string> dictionary3 = gList.ToDictionary(guest=>guest.Name,g=>g.Tel);
      foreach (var s in dictionary3)
      {
        Console.WriteLine("键值{0}:{1}", s.Key, s.Value);
      }
      Console.WriteLine("--------------------------------");
      Console.ReadKey();
      //d.自定义比较器
      Dictionary<string, string> dictionary4 = gList.ToDictionary(guest=>guest.Name,g=>g.Tel,new MyEqualityComparer<string>());
      foreach (var s in dictionary4)
      {
        Console.WriteLine("键值{0}:{1}", s.Key, s.Value);
      }
      Console.WriteLine("------------------------------------------------------");
      Console.ReadKey();


      ///////////////
      ///4.ToLookup用于将序列转换为泛型Lookup<TKey,TValue>。
      ///Dictionary和Lookup是非常近似的一对类型，都通过“键”访问相关的元素，不同的是Dictionary的Key和Value是一一对应关系
      ///Lookup的Key和Value是一对多关系
      ///Lookup没有公共构造函数，时能用ToLookup构建，创建后也不能删除Lookup中的元素。
      ///该方法也有4个原型，和上面的ToDictionary极像
      ///
      //a. Name的第一个字符(字符串)作key
      ILookup<string, GuestInfo> lookup1 = gList.ToLookup(guest => guest.Name.Substring(0, 1));
      foreach (var k in lookup1)
      {
        Console.WriteLine(k.Key);//键值
        foreach (var v in k)
        {
          Console.Write("{0},{1},{2}",v.Name,v.Age,v.Tel );
        }
        Console.WriteLine();
      }
      Console.WriteLine("--------------------------------");
      Console.ReadKey();
      //b自定义比较器
      ILookup<string, GuestInfo> lookup2 = gList.ToLookup(guest => guest.Name.Substring(0, 1), new MyEqualityComparer<string>());
      foreach (var k in lookup2)
      {
        Console.WriteLine(k.Key);//键值
        foreach (var v in k)
        {
          Console.Write("{0},{1},{2}", v.Name, v.Age, v.Tel);
        }
        Console.WriteLine();
      }
      Console.WriteLine("--------------------------------");
      Console.ReadKey();
      //c
      ILookup<string, string> lookup3 = gList.ToLookup(guest=>guest.Name.Substring(0,1),g=>g.Name );
      foreach (var k in lookup3)
      {
        Console.WriteLine(k.Key);//键值
        foreach (var v in k)
        {
          Console.Write("{0} ", v);
        }
        Console.WriteLine();
      }
      Console.WriteLine("--------------------------------");
      Console.ReadKey();
      //d自定义比较器
      ILookup<string, string> lookup4 = gList.ToLookup(guest=>guest.Name.Substring(0,1),g=>g.Name,new MyEqualityComparer<string>());
      foreach (var k in lookup4)
      {
        Console.WriteLine(k.Key);//键值
        foreach (var v in k)
        {
          Console.Write("{0} ", v);
        }
        Console.WriteLine();
      }
      Console.WriteLine("--------------------------------");
      Console.ReadKey();
    }
  }
}

								 
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