The document discusses .NET 4.0's System.Runtime.Caching library. It begins with an agenda that includes discussing features, components, development flow, and demos. The main components covered are ObjectCache, which provides caching methods and properties, and ChangeMonitor, which monitors dependencies of cached items. Examples are provided of using CacheItemPolicy to set expiration policies and using different ChangeMonitor implementations like HostFileChangeMonitor. The document concludes with references to documentation, code samples, and a question and answer section.

1. .NET 4.0 - SYSTEM.RUNTIME.CACHING
Larry Nung

2. AGENDA
Feature
Component
Develop Flow
DEMO
Reference
Q & A
2

3. FEATURE

4. FEATURE
 可擴充
 可套用至所有 .NET Framework 應用程式
 內建記憶體快取的實現
 主要是在擴展性方面做了改進
 改變了原來只能利用內存進行緩存的侷限
 允許用戶在不改變代碼的情況下通過修改配置的方式，靈活的切換緩存
介質

5. COMPONENT

6. OBJECTCACHE
 記憶體快取框架中的主要類別
 提供存取物件快取所需方法和屬性
 支援加入、擷取與更新快取資料
 主要任務為建立管理快取元素、指定快取回收與到期資訊、觸發元件變更事件。
 快取框架中所提供的MemoryCache類別即為ObjectCache抽象類別的實作

7. OBJECTCACHE

8. OBJECTCACHE

9. OBJECTCACHE

10. OBJECTCACHE

11. CHANGEMONITOR
 為一抽象基底類別
 用以監控快取項目所依存之資料的狀態變更
 可監控快取介質的狀態並判斷快取是否過期需要更新，透過適當的設定
可讓資料在享有快取好處的同時也能保證資料不至於過時
 快取框架中的CacheEntryChangeMonitor、FileChangeMonitor、
HostFileChangeMonitor、SqlChangeMonitor等類別都是該抽象類別的
實作

12. CHANGEMONITOR

13. CHANGEMONITOR

14. CHANGEMONITOR

15. CACHEITEMPOLICY
 快取項目收回和期限的詳細資料

16. CACHEITEMPOLICY

17. CACHEITEMPOLICY

18. DEVELOP FLOW

19. DEVELOP FLOW
 Assembly
 System.Runtime.Caching.dll
 Namespace
 System.Runtime.Caching

20. DEVELOP FLOW
using System.Runtime.Caching;
...
private ObjectCache _cache;
private ObjectCache m_Cache
{
get {
if (_cache == null)
_cache = MemoryCache.Default;
return _cache;
}
}
...
const string CACHE_KEY = "Content";
var content = m_Cache[CACHE_KEY] as string;
if (content == null) {
m_Cache.Set(CACHE_KEY, GetContent(), GetPolicy());
}
Init
ObjectCache
Set Content &
CacheItemPolicy
to ObjectCache
Get content from
cache

21. DEMO
CacheItemPolicy
larrynung/CacheItemPolicyDemo

22. CACHEITEMPOLICY
…
public String GetContent() {
const string CACHE_KEY = "Content";
string content = m_Cache[CACHE_KEY] as string;
if (content == null) {
CacheItemPolicy policy = new CacheItemPolicy();
//policy.AbsoluteExpiration = DateTime.Now.AddMilliseconds(1500);
policy.SlidingExpiration = TimeSpan.FromMilliseconds(1500);
//policy.UpdateCallback = new CacheEntryUpdateCallback((args) => {
// Console.WriteLine("MyCachedItemUpdatedCallback...");
// Console.WriteLine(string.Format("Remove {0}...Because {1}",args.Key,args.RemovedReason.ToString()));
// Console.WriteLine(new string('=', 50)); //});
//policy.RemovedCallback = new CacheEntryRemovedCallback((args) => {
//Console.WriteLine("CacheEntryRemovedCallback...");
//Console.WriteLine(string.Format("Remove {0}...Because {1}", args.CacheItem.Key, args.RemovedReason.ToString()));
Console.WriteLine(new string('=', 50)); });
content = Guid.NewGuid().ToString();
Thread.Sleep(1000);
m_Cache.Set(CACHE_KEY, content, policy);
}
return content;
}
…

23. DEMO
HostFileChangeMonitor
larrynung/HostFileChangeMonitorDemo

24. HOSTFILECHANGEMONITOR
…
public String GetContent() {
const string CACHE_KEY = "Content";
string content = m_Cache[CACHE_KEY] as string;
if (content == null) {
CacheItemPolicy policy = new CacheItemPolicy();
policy.SlidingExpiration = TimeSpan.FromMilliseconds(1500);
var changeMonitor = new HostFileChangeMonitor(new List<string> { File });
policy.ChangeMonitors.Add(changeMonitor);
content = System.IO.File.ReadAllText(File);
Thread.Sleep(1000);
m_Cache.Set(CACHE_KEY, content, policy);
}
return content;
}
…

25. DEMO
Custom ChangeMonitor
larrynung/CustomChangeMonitorDemo

26. CUSTOM CHANGEMONITOR
using System.Runtime.Caching;
...
public class ClipboardChangeMonitor : ChangeMonitor {
...
private string m_ClipboardText {
get { return _clipboardText ?? string.Empty; }
set {
if (_clipboardText == value) return;
_clipboardText = value;
OnChanged(value);
}
}
public override string UniqueId {
get { return _uniqueID ?? (_uniqueID = Guid.NewGuid().ToString()); }
}
public ClipboardChangeMonitor() {
m_Timer.Interval = 1000;
m_Timer.Tick += m_Timer_Tick;
m_Timer.Start();
_clipboardText = Clipboard.GetText();
InitializationComplete();
}
...
void m_Timer_Tick(object sender, EventArgs e) {
m_ClipboardText = Clipboard.GetText();
}
}

27. REFERENCE
27

28. REFERENCE
 .NET 4.0 New Feature - System.Runtime.Caching - Level Up- 點部落
 http://www.dotblogs.com.tw/larrynung/archive/2010/11/26/19746.aspx
 How to customize .NET 4.0's
System.Runtime.Caching.ChangeMonitor - Level Up- 點部落
 http://www.dotblogs.com.tw/larrynung/archive/2013/06/12/105458.aspx
 How to: Cache Objects Simply using
System.Runtime.Caching.MemoryCache - CodeProject
 http://www.codeproject.com/Articles/756423/How-to-Cache-Objects-Simply-
using-System-Runtime-C

29. REFERENCE
 larrynung/CacheItemPolicyDemo
 https://github.com/larrynung/CacheItemPolicyDemo
 ObjectCache 類別 (System.Runtime.Caching)
 https://msdn.microsoft.com/zh-
tw/library/system.runtime.caching.objectcache(v=vs.110).aspx
 MemoryCache 類別 (System.Runtime.Caching)
 https://msdn.microsoft.com/zh-tw/library/dd780634(v=vs.110).aspx

30. REFERENCE
 CacheItemPolicy 類別 (System.Runtime.Caching)
 https://msdn.microsoft.com/zh-
tw/library/system.runtime.caching.cacheitempolicy(v=vs.110).aspx
 ChangeMonitor 類別 (System.Runtime.Caching)
 https://msdn.microsoft.com/zh-
tw/library/system.runtime.caching.changemonitor(v=vs.110).aspx

31. Q&A
31

32. QUESTION & ANSWER
32