1 using System;
 2 using System.Collections.Generic;
 3 using System.Linq;
 4 using System.Text;
 5 using System.Threading.Tasks;
 6 using static System.Console;
 7
 8 namespace LearnForCSharp
 9 {
10     class Program
11     {
12         static void Main(string[] args)
13         {
14             try
15             {
16                 Currency balance = new Currency(50, 35);
17
18                 WriteLine(balance);
19                 WriteLine(balance.ToString());
20
21                 float balance2 = balance;
22
23                 WriteLine(balance2);
24
25                 checked
26                 {
27                     Currency balance3 = (Currency)balance2;
28
29                     WriteLine(balance3.ToString());
30                     WriteLine(balance3);
31                 }
32
33                 checked
34                 {
35                     Currency balance3 = (Currency)(-50.50);
36
37                     WriteLine(balance3.ToString());
38                     WriteLine(balance3);
39                 }
40             }
41             catch (Exception e)
42             {
43                 WriteLine("Exception occurred:" + e.Message);
44             }
45
46             ReadKey();
47         }
48     }
49
50     struct Currency
51     {
52         public uint Dollars;
53         public ushort Cents;
54
55         public Currency(uint dollars, ushort cents)
56         {
57             this.Dollars = dollars;
58             this.Cents = cents;
59         }
60
61         public Currency(Currency c)
62         {
63             this.Dollars = c.Dollars;
64             this.Cents = c.Cents;
65         }
66
67         public override string ToString()
68         {
69             return string.Format("${0}.{1,-2:00}", Dollars, Cents);
70         }
71
72         public static implicit operator float(Currency value)
73         {
74             return value.Dollars + (value.Cents / 100.0f);
75         }
76
77         public static explicit operator Currency(float value)
78         {
79             //确保类型强制转换本身也在checked环境下
80             checked
81             {
82                 uint dollars = (uint)value;
83                 //强制转换导致的精度丢失
84                 //ushort cents = (ushort)((value - dollars) * 100);
85                 ushort cents = Convert.ToUInt16((value - dollars) * 100);
86
87                 return new Currency(dollars, cents);
88             }
89         }
90     }
91 }