Item 5: Always Provide ToString()(Effective C#)

1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using System.Text;
5
6 namespace EffectiveCSharpItem5
7 {
8 public class Customer : IFormattable
9 {
10 public string Name
11 {
12 get;
13 set;
14 }
15
16 public decimal Revenue
17 {
18 get;
19 set;
20 }
21
22 public string ContactPhone
23 {
24 get;
25 set;
26 }
27
28 public override string ToString()
29 {
30 return Name;
31 }
32
33 string System.IFormattable.ToString(string format, IFormatProvider formatProvider)
34 {
35 if (formatProvider != null)
36 {
37 ICustomFormatter fmt = formatProvider.GetFormat(this.GetType()) as ICustomFormatter;
38 if (fmt != null)
39 {
40 return fmt.Format(format, this, formatProvider);
41 }
42 }
43
44 switch (format)
45 {
46 case "r":
47 return Revenue.ToString();
48 case "p":
49 return ContactPhone;
50 case "nr":
51 return string.Format("{0,20}, {1,10:C}", Name, Revenue);
52 case "np":
53 return string.Format("{0,20}, {1,15}", Name, ContactPhone);
54 case "pr":
55 return string.Format("{0,15}, {1,10:C}", ContactPhone, Revenue);
56 case "pn":
57 return string.Format("{0,15}, {1,20}", ContactPhone, Name);
58 case "rn":
59 return string.Format("{0,10:C}, {1,20}", Revenue, Name);
60 case "rp":
61 return string.Format("{0,10:C}, {1,20}", Revenue, ContactPhone);
62 case "nrp":
63 return string.Format("{0,20}, {1,10:C}, {2,15}", Name, Revenue, ContactPhone);
64 case "npr":
65 return string.Format("{0,20}, {1,15}, {2,10:C}", Name, ContactPhone, Revenue);
66 case "pnr":
67 return string.Format("{0,15}, {1,20}, {2,10:C}", ContactPhone, Name, Revenue);
68 case "prn":
69 return string.Format("{0,15}, {1,10:C}, {2,15}", ContactPhone, Revenue, Name);
70 case "rpn":
71 return string.Format("{0,10:C}, {1,15}, {2,20}", Revenue, ContactPhone, Name);
72 case "rnp":
73 return string.Format("{0,10:C}, {1,20}, {2,15}", Revenue, Name, ContactPhone);
74 case "n":
75 case "G":
76 default:
77 return Name;
78 }
79 }
80 }
81
82 public class CustomFormatter : IFormatProvider, ICustomFormatter
83 {
84 #region IFormatProvider Members
85
86 public object GetFormat(Type formatType)
87 {
88 if (formatType == typeof(ICustomFormatter))
89 {
90 return this;
91 }
92 return null;
93 }
94
95 #endregion
96
97 #region ICustomFormatter Members
98
99 public string Format(string format, object arg, IFormatProvider formatProvider)
{
Customer c = arg as Customer;
if (c == null)
{
return arg.ToString();
}

return string.Format("{0,50}, {1,15}, {2,10:C}", c.Name, c.ContactPhone, c.Revenue);
}

#endregion
}

class Program
{
static void Main(string[] args)
{
IFormattable c1 = new Customer() { Name="Ray", ContactPhone="12345", Revenue=200000 };

Console.WriteLine("Customer record: {0}", c1.ToString("nrp", null));
Console.WriteLine(string.Format(new CustomFormatter(), "{0}", c1));
Console.Read();
}
}
}