CacheItem Class

Definition

public ref class CacheItem

public class CacheItem

type CacheItem = class

Public Class CacheItem

Inheritance

Object

CacheItem

Examples

The following example shows how to use the CacheItem class to store the contents of a file as a cache entry.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Runtime.Caching;
using System.IO;

public partial class _Default : System.Web.UI.Page
{

    protected void Button1_Click(object sender, EventArgs e)
    {
        ObjectCache cache = MemoryCache.Default;

        CacheItem fileContents = cache.GetCacheItem("filecontents");

        if (fileContents == null)
        {
            CacheItemPolicy policy = new CacheItemPolicy();

            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
            string fileData = File.ReadAllText(cachedFilePath);

            fileContents = new CacheItem("filecontents", fileData);

            cache.Set(fileContents, policy);
        }
        Label1.Text = (fileContents.Value as string);
    }
}

Imports System.Runtime.Caching
Imports System.IO

Partial Class _Default
    Inherits System.Web.UI.Page

    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 CacheItem = cache.GetCacheItem("filecontents")

        If fileContents Is Nothing Then
            Dim policy As New CacheItemPolicy()

            Dim filePaths As New List(Of String)()

            Dim CachedFilePaths As String = Server.MapPath("~") & "\cacheText.txt"

                filePaths.Add(CachedFilePaths)

            policy.ChangeMonitors.Add(New HostFileChangeMonitor(filePaths))

            ' Fetch the file contents 
            Dim fileData As String = File.ReadAllText(CachedFilePaths)

            fileContents = New CacheItem("filecontents", fileData)

            cache.Set(fileContents, policy)
        End If
        Label1.Text = TryCast(fileContents.Value, String)
    End Sub
End Class

Remarks

The CacheItem class provides a logical representation of a cache entry, which can include regions by using the RegionName property. In the default ASP.NET cache implementation, a cache entry is a key/value pair.

Entries in the cache are not CacheItem instances. Instead, the cache provider can store cache entries in any internal format that is convenient. However, the cache API requires cache providers to be able to convert cache entries into CacheItem instances (and vice versa).

Custom cache implementations can inherit from the CacheItem class provide additional information about cache entries.

Notes to Inheritors

The ObjectCache class has methods that support adding, fetching, and updating cache data, and all these methods have overloads that support the CacheItem class. Therefore, a custom cache implementation can create an extended CacheItem class and use that extended class together with the existing ObjectCache API for cache entries.

Constructors

Properties

Methods

Applies to

See also

• ObjectCache