CacheItemPolicy Class
Represents a set of eviction and expiration details for a specific cache entry.
Assembly: System.Runtime.Caching (in System.Runtime.Caching.dll)
The CacheItemPolicy type exposes the following members.
| Name | Description | |
|---|---|---|
![]() | AbsoluteExpiration | Gets or sets a value that indicates whether a cache entry should be evicted after a specified duration. |
![]() | ChangeMonitors | Gets a collection of ChangeMonitor objects that are associated with a cache entry. |
![]() | Priority | Gets or sets a priority setting that is used to determine whether to evict a cache entry. |
![]() | RemovedCallback | Gets or sets a reference to a CacheEntryRemovedCallback delegate that is called after an entry is removed from the cache. |
![]() | SlidingExpiration | Gets or sets a value that indicates whether a cache entry should be evicted if it has not been accessed in a given span of time. |
![]() | UpdateCallback | Gets or sets a reference to a CacheEntryUpdateCallback delegate that is called before a cache entry is removed from the cache. |
| Name | Description | |
|---|---|---|
![]() | Equals(Object) | Determines whether the specified Object is equal to the current Object. (Inherited from Object.) |
![]() | Finalize | Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.) |
![]() | GetHashCode | Serves as a hash function for a particular type. (Inherited from Object.) |
![]() | GetType | Gets the Type of the current instance. (Inherited from Object.) |
![]() | MemberwiseClone | Creates a shallow copy of the current Object. (Inherited from Object.) |
![]() | ToString | Returns a string that represents the current object. (Inherited from Object.) |
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 ImplementersThe CacheItemPolicy type is unsealed so that custom cache developers can extend it.
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.
[Visual Basic]
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
[C#]
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;
}
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
