CacheItemPolicy Class

Definition

public ref class CacheItemPolicy

public class CacheItemPolicy

type CacheItemPolicy = class

Public Class CacheItemPolicy

Inheritance

Object

CacheItemPolicy

Examples

The following example shows how to create an in-memory cache item that monitors the path for a text file. The cache creates a CacheItemPolicy object and sets the AbsoluteExpiration property to evict the cache after 60 seconds.

Protected Sub Button1_Click(ByVal sender As Object, _
 ByVal e As System.EventArgs) Handles Button1.Click
 Dim cache As ObjectCache = MemoryCache.Default
 Dim fileContents As String = TryCast(cache("filecontents"), _
 String)
 If fileContents Is Nothing Then
 Dim policy As New CacheItemPolicy()
 policy.AbsoluteExpiration = _
 DateTimeOffset.Now.AddSeconds(60.0)
 Dim filePaths As New List(Of String)()
 Dim cachedFilePath As String = Server.MapPath("~") & _
 "\cacheText.txt"
 filePaths.Add(cachedFilePath)
 policy.ChangeMonitors.Add(New _
 HostFileChangeMonitor(filePaths))

 ' Fetch the file contents.
 fileContents = File.ReadAllText(cachedFilePath)
 cache.Set("filecontents", fileContents, policy)
 End If
 Label1.Text = fileContents
End Sub

protected void Button1_Click(object sender, EventArgs e)
 {
 ObjectCache cache = MemoryCache.Default;
 string fileContents = cache["filecontents"] as string;
 if (fileContents == null)
 {
 CacheItemPolicy policy = new CacheItemPolicy();
 policy.AbsoluteExpiration =
 DateTimeOffset.Now.AddSeconds(60.0);

 List<string> filePaths = new List<string>();
 string cachedFilePath = Server.MapPath("~") +
 "\\cacheText.txt";
 filePaths.Add(cachedFilePath);

 policy.ChangeMonitors.Add(new
 HostFileChangeMonitor(filePaths));

 // Fetch the file contents.
 fileContents = File.ReadAllText(cachedFilePath);

 cache.Set("filecontents", fileContents, policy);

 }

 Label1.Text = fileContents;
 }

Remarks

A CacheItemPolicy instance contains information that can be associated with a cache entry. For example, when a cache entry is about to be removed from the cache, a CacheEntryUpdateArguments object is passed to a callback method. The UpdatedCacheItemPolicy property of the CacheEntryUpdateArguments object can pass a reference to a CacheItemPolicy instance that can include eviction and expiration details about the cache entry.

Some methods in the MemoryCache and ObjectCache classes accept a CacheItemPolicy instance to describe eviction or expiration policy.

Notes to Inheritors

The CacheItemPolicy type is unsealed so that custom cache developers can extend it.