1 using System.Collections; 
 2 
 3 using System.Collections.Generic; 
 4 
 5 using System.Linq; 
 6 
 7  
 8 
 9 namespace Chapter_5 
10 
11 { 
12 
13     class Program 
14 
15     { 
16 
17         static void Main(string[] args) 
18 
19         { 
20 
21  
22 
23             IList<Person> persons = new
 
 List<Person>(); 
24 
25             IList<int> numbers = new List<int>(); 
26 
27             IList<string> names = new List<string>(); 
28 
29  
30 
31             var defaultPersons = persons.DefaultIfEmpty(); 
32 
33  
34 
35             var defaultNumbers = numbers.DefaultIfEmpty().ToList(); 
 
36 
37  
38 
39             var defaultNames = names.DefaultIfEmpty(); 
40 
41         } 
42 
43     } 
44 
45  
46 
47     class Person 
48 
49     { 
50 
51         public string Name 
52 
53         { 
54 
55             get; 
56 
57             set; 
58 
59         } 
60 
61  
62 
63         public
 
 string Address 
64 
65         { 
66 
67             get; 
68 
69             set; 
70 
71         } 
72 
73  
74 
75         public int Age 
76 
77         { 
78 
79             get; 
80 
81             set; 
82 
83         } 
84 
85     } 
86 
87 }