C#中字典的使用Dictionary

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace 集合

{

class 字典

{

public static void Main()

{

//字典也称映射或者散列表，主要特点是可以根据键快速查找值，也可以自由删除添加元素

//在删除添加时，不会像列表一样，移动之后的所有元素，产生内存的开销。

//.net中提供了几个字典，可以使用最主要的类是Dictionary<TKey,TValue>

//这个类与我们上面说的SortedList用法完全一样，这里不再多说了。

//键的类型　　

//用做字典中键的类型必须重写Object类中的GetHashCode()方法,只要字典类需要确定元素的位置，就要调用本方法

//字典内部通过调用这个方法的返回值，来计算产生散列。。这个算法不做介绍　，但我要知道，它涉及到素数

//所以字典的容量是一个素数

//GetHashCode()方法的实现需要遵循以下几点

// 1 相同的对象应总是返回相同的值

// 2 不同的对象可以返回相同的值

// 3 应执行得比较快，计算的开销不大。

// 4 不能刨出异常

// 5 应至少使用一个实例字段

// 6 散列码值应平均分布在int可以存储的整个数字区上

// 7 散列码最好在对象的生存期中不发生变化

//提示：　字典的性能取决于GetHashCode()方法的实现代码

Dictionary<EmployeeID , Employee> emps = new Dictionary<EmployeeID,Employee>(31) ;

EmployeeID idAladdin = new EmployeeID( "C7102" ) ;

Employee aladdin = new Employee( "aladdin" , 5000.00m , idAladdin ) ;

emps.Add( idAladdin , aladdin ) ;

Console.WriteLine( aladdin ) ;

EmployeeID idjacky = new EmployeeID( "C7106" ) ;

Employee jacky = new Employee( "jacky" , 5000.00m , idjacky ) ;

emps.Add( idjacky , jacky ) ;

Console.WriteLine( jacky ) ;

EmployeeID idzhao = new EmployeeID( "C8102" ) ;

Employee zhao = new Employee( "zhao" , 5000.00m , idzhao ) ;

emps.Add( idzhao , zhao ) ;

Console.WriteLine( zhao ) ;

EmployeeID idxiaofei = new EmployeeID( "C9102" ) ;

Employee xiaofei = new Employee( "xiaofei" , 5000.00m , idxiaofei ) ;

emps.Add( idxiaofei , xiaofei ) ;

Console.WriteLine( xiaofei ) ;

EmployeeID iddabi = new EmployeeID( "C7602" ) ;

Employee dabi = new Employee( "dabi" , 5000.00m , iddabi ) ;

emps.Add( iddabi , dabi ) ;

Console.WriteLine( dabi ) ;

EmployeeID idalong = new EmployeeID( "C7302" ) ;

Employee along = new Employee( "along" , 5000.00m , idalong ) ;

emps.Add( idalong , along ) ;

Console.WriteLine( along ) ;

EmployeeID idcarl = new EmployeeID( "C7402" ) ;

Employee carl = new Employee( "carl" , 5000.00m , idcarl ) ;

emps.Add( idcarl , carl ) ;

Console.WriteLine( carl ) ;

EmployeeID idjeff = new EmployeeID( "C7502" ) ;

Employee jeff = new Employee( "jeff" , 5000.00m , idjeff ) ;

emps.Add( idjeff , jeff ) ;

Console.WriteLine( jeff ) ;

EmployeeID iddenny = new EmployeeID( "C6602" ) ;

Employee denny = new Employee( "denny" , 5000.00m , iddenny ) ;

emps.Add( iddenny , denny ) ;

Console.WriteLine( denny ) ;

EmployeeID idmatt = new EmployeeID( "C7701" ) ;

Employee matt = new Employee( "matt" , 5000.00m , idmatt ) ;

emps.Add( idmatt , matt ) ;

Console.WriteLine( matt ) ;

Console.ReadLine() ;

}

}

struct EmployeeID : IEquatable<EmployeeID>

{

private readonly char prefix ;

private readonly int number ;

public EmployeeID( string id )

{

this.prefix = (id.ToUpper())[0] ;

int numLength = id.Length - 1 ;

this.number = int.Parse( id.Substring( 1 , numLength > 6 ? 6 : numLength ) ) ;

}

public override string ToString()

{

return this.prefix.ToString() + string.Format( "{0,6:000000}" , number ) ;

}

public override int GetHashCode()

{

return ( number ^ number << 16 ) * 0x15051505 ;

}

public bool Equals( EmployeeID other )

{

return ( other.number == this.number && this.prefix == other.prefix ) ;

}

}

class Employee

{

private string name ;

private decimal salary ;

private readonly EmployeeID id ;

public Employee( string name , decimal salary , EmployeeID id )

{

this.name = name ;

this.salary = salary ;

this.id = id ;

}

public override string ToString()

{

return string.Format( "{0} : {1,-20} {2:C}" , id.ToString() , name,salary ) ;

}

}

}