1+ using System ;
2+ using System . Collections . Generic ;
3+ using System . Threading ;
4+ using GenericMemoryCache ;
5+ using Microsoft . Extensions . Caching . Memory ;
6+
7+ namespace Sample
8+ {
9+ class Program
10+ {
11+ static void Main ( string [ ] args )
12+ {
13+ // non-generic MemoryCache instance
14+ IMemoryCache nonGeneric = new MemoryCache ( new MemoryCacheOptions ( ) ) ;
15+
16+ // GenericMemoryCache
17+ IMemoryCache < int , Book > booksCache = nonGeneric . ToGeneric < int , Book > ( ) ;
18+
19+ Book CreateValue ( ICacheEntry < int , Book > entry )
20+ {
21+ entry . SetAbsoluteExpiration ( TimeSpan . FromSeconds ( 2 ) ) ;
22+ Console . WriteLine ( $ "id = { entry . Key } created") ;
23+ return entry . Value ;
24+ }
25+
26+ // GetOrCreate
27+ Book asp1 = booksCache . GetOrCreate ( 1 , CreateValue ) ;
28+ // id = 1 created
29+
30+ Book scala1 = booksCache . GetOrCreate ( 2 , CreateValue ) ;
31+ // id = 2 created
32+
33+ // cached
34+ Book asp2 = booksCache . GetOrCreate ( 1 , CreateValue ) ;
35+ Console . WriteLine ( $ "asp1 == asp2(cached): { asp1 == asp2 } ") ; // true
36+
37+ // Remove
38+ booksCache . Remove ( 2 ) ;
39+
40+ // Create
41+ Book scala2 = booksCache . GetOrCreate ( 2 , CreateValue ) ;
42+ Console . WriteLine ( $ "scala1 == scala2(created): { scala1 == scala2 } ") ; // false
43+
44+ // Expire
45+ Thread . Sleep ( TimeSpan . FromSeconds ( 5 ) ) ;
46+
47+ // Create
48+ Book scala3 = booksCache . GetOrCreate ( 2 , CreateValue ) ;
49+ // id = 2 created
50+
51+ Console . WriteLine ( "end." ) ;
52+ Console . ReadLine ( ) ;
53+ }
54+ }
55+
56+ // てきとうなデータベースのかわり
57+ public static class Database
58+ {
59+ private static Dictionary < int , Book > BooksDic = new Dictionary < int , Book > ( )
60+ {
61+ {
62+ 1 , new Book ( )
63+ {
64+ Id = 1 ,
65+ Title = "Programming ASP.NET" ,
66+ Stock = 5
67+ }
68+ } ,
69+ {
70+ 2 , new Book ( )
71+ {
72+ Id = 2 ,
73+ Title = "Programming in Scala" ,
74+ Stock = 10
75+ }
76+ }
77+ } ;
78+
79+ public static Book SelectBook ( int id ) => BooksDic . TryGetValue ( id , out Book book ) ? book . DeepCopy ( ) : null ;
80+ }
81+
82+ public class Book
83+ {
84+ public int Id { get ; set ; }
85+ public string Title { get ; set ; }
86+ public int Stock { get ; set ; }
87+
88+ public Book DeepCopy ( )
89+ => new Book ( )
90+ {
91+ Id = this . Id ,
92+ Title = this . Title ,
93+ Stock = this . Stock
94+ } ;
95+ }
96+ }
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