Represents an object that monitors changes to files.
Assembly: System.Runtime.Caching (in System.Runtime.Caching.dll)
Thetype exposes the following members.
|FilePaths||Gets a collection that contains the paths of files that are monitored for changes.|
|HasChanged||Gets a value that indicates that the state that is monitored by the ChangeMonitor class has changed. (Inherited from ChangeMonitor.)|
|IsDisposed||Gets a value that indicates that the derived instance of a ChangeMonitor class is disposed. (Inherited from ChangeMonitor.)|
|LastModified||Gets a value that indicates the last time that a file that is being monitored was changed.|
|UniqueId||Gets a value that represents the ChangeMonitor class instance. (Inherited from ChangeMonitor.)|
|Dispose||Releases all resources that are used by the current instance of the ChangeMonitor class. (Inherited from ChangeMonitor.)|
|Dispose(Boolean)||Releases all managed and unmanaged resources and any references to the ChangeMonitor instance. This overload must be implemented by derived change-monitor classes. (Inherited from ChangeMonitor.)|
|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.)|
|InitializationComplete||Called from the constructor of derived classes to indicate that initialization is finished. (Inherited from ChangeMonitor.)|
|MemberwiseClone||Creates a shallow copy of the current Object. (Inherited from Object.)|
|NotifyOnChanged||Called by Cache implementers to register a callback and notify an ObjectCache instance through the OnChangedCallback delegate when a dependency has changed. (Inherited from ChangeMonitor.)|
|OnChanged||Called by derived classes to raise the event when a dependency changes. (Inherited from ChangeMonitor.)|
|ToString||Returns a string that represents the current object. (Inherited from Object.)|
The class is a base ChangeMonitor type for classes that monitor changes to files. To create a monitor for changes in the file system, you can inherit from this class.Notes to Inheritors
For information about the inheritance contract that must be followed, see the Notes for Inheritors section in the ChangeMonitor class overview.
The following example shows how to create a cache item that uses a HostFileChangeMonitor object to monitor the state of the source data (a file) on the file system. The HostFileChangeMonitor class inherits from the class. The cache entry is defined using a CacheItemPolicy object that provides eviction and expiration details for the cache entry.
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 String = TryCast(cache("filecontents"), _ String) If fileContents Is Nothing Then Dim policy As New CacheItemPolicy() policy.AbsoluteExpiration = _ DateTimeOffset.Now.AddSeconds(10.0) 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) & _ vbCrLf & DateTime.Now.ToString() cache.Set("filecontents", fileContents, policy) End If Label1.Text = fileContents End Sub End Class
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