ASP.NET Tutorial/Cache/CacheDependency

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Creating an RssCacheDependency class (C#)

   <source lang="csharp">

<%@ Page Language="C#" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" > <head id="Head1" runat="server"> 

   <title>Custom Cache Dependency Example</title>

</head> <body> 

   <form id="Form1" runat="server"> RSS URL:
      <asp:TextBox ID="TextBox1" Runat="server"/>
      <asp:Button ID="Button1" onclick="Button1_Click" Runat="server" 
       Text="Get RSS" />
       Cached:<asp:Label ID="Label2" Runat="server"></asp:Label>

       RSS:

       <asp:TextBox ID="TextBox2" Runat="server" TextMode="MultiLine"
        Width="800px" Height="300px"></asp:TextBox>
   </form>

</body> </html> <script runat="server"> 

   void Button1_Click(object sender, System.EventArgs e)
   {
       string RSSUrl = TextBox1.Text;
       Label2.Text = "Loaded From Cache";
       if (Cache[TextBox1.Text] == null)
       {
           Label2.Text = "Loaded Fresh";
           RssCacheDependency itDepends = new RssCacheDependency(RSSUrl, 600);
           Cache.Insert(RSSUrl, itDepends.Document, itDepends);
       }
       TextBox2.Text = ((System.Xml.XmlDocument)Cache[TextBox1.Text]).OuterXml;
   }

</script>

File: App_Code\RssCacheDependency.cs using System; using System.Web; using System.Threading; using System.Web.Caching; using System.Xml; public class RssCacheDependency : CacheDependency { 

   static Timer backgroundThread;
   int howOften = 900;
   XmlDocument RSS;
   string RSSUrl;
   public RssCacheDependency(string URL, int polling)
   {
       howOften = polling;
       RSSUrl = URL;
       RSS = RetrieveRSS(RSSUrl);
       if (backgroundThread == null)
       {
           backgroundThread = new Timer(
                  new TimerCallback(CheckDependencyCallback),
                  this, (howOften * 1000), (howOften * 1000));
       }
   }
   public XmlDocument RetrieveRSS(string URL)
   {
       XmlDocument retVal = new XmlDocument();
       retVal.Load(URL);
       return retVal;
   }
   public void CheckDependencyCallback(object sender)
   {
       RssCacheDependency CacheDepends = sender as RssCacheDependency;
       XmlDocument NewRSS = RetrieveRSS(RSSUrl);
       if (NewRSS.OuterXml != RSS.OuterXml)
       {
           CacheDepends.NotifyDependencyChanged(CacheDepends, EventArgs.Empty);
       }
   }
   override protected void DependencyDispose()
   {
       backgroundThread = null;
       base.DependencyDispose();
   }
   public XmlDocument Document
   {
       get
       {
           return RSS;
       }
   }

}</source>


Creating an RssCacheDependency class (VB)

   <source lang="csharp">

<%@ Page Language="VB" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" > <head id="Head1" runat="server"> 

   <title>Custom Cache Dependency Example</title>

</head> <body> 

   <form id="Form1" runat="server"> RSS URL:
      <asp:TextBox ID="TextBox1" Runat="server"/>
      <asp:Button ID="Button1" onclick="Button1_Click" Runat="server" 
       Text="Get RSS" />
       Cached:<asp:Label ID="Label2" Runat="server"></asp:Label>

       RSS:

       <asp:TextBox ID="TextBox2" Runat="server" TextMode="MultiLine"
        Width="800px" Height="300px"></asp:TextBox>
   </form>

</body> </html>

<script runat="server"> 

   Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs)
       Dim RSSUrl As String = TextBox1.Text
       Label2.Text = "Loaded From Cache"
       If Cache(TextBox1.Text) Is Nothing Then
           Label2.Text = "Loaded Fresh"
           Dim itDepends As New RssCacheDependency(RSSUrl, 600)
           Cache.Insert(RSSUrl, itDepends.Document, itDepends)
       End If
       TextBox2.Text = CType(Cache(TextBox1.Text), _ 
           System.Xml.XmlDocument).OuterXml
   End Sub

</script> File: App_Code\RssCacheDependency.vb Imports System Imports System.Web Imports System.Threading Imports System.Web.Caching Imports System.Xml Public Class RssCacheDependency 

   Inherits CacheDependency
   Shared backgroundThread As Timer
   Dim howOften As Integer = 900
   Dim RSS As XmlDocument
   Dim RSSUrl As String
   Public Sub New(ByVal URL As String, ByVal polling As Integer)
       howOften = polling
       RSSUrl = URL
       RSS = RetrieveRSS(RSSUrl)
       If backgroundThread Is Nothing Then
           backgroundThread = New Timer( _
               New TimerCallback(AddressOf CheckDependencyCallback), _
               Me, (howOften * 1000), (howOften * 1000))
       End If
   End Sub
   Function RetrieveRSS(ByVal URL As String) As XmlDocument
       Dim retVal As New XmlDocument
       retVal.Load(URL)
       Return retVal
   End Function
   Public Sub CheckDependencyCallback(ByVal Sender As Object)
       Dim CacheDepends As RssCacheDependency = _
           CType(Sender, RssCacheDependency)
       Dim NewRSS As XmlDocument = RetrieveRSS(RSSUrl)
       If Not NewRSS.OuterXml = RSS.OuterXml Then
           CacheDepends.NotifyDependencyChanged(CacheDepends, EventArgs.Empty)
       End If
   End Sub
   Protected Overrides Sub DependencyDispose()
       backgroundThread = Nothing
       MyBase.DependencyDispose()
   End Sub
   Public ReadOnly Property Document() As XmlDocument
       Get
           Return RSS
       End Get
   End Property

End Class</source>

Источник — «http://www.nfex.ru/index.php?title=ASP.NET_Tutorial/Cache/CacheDependency&oldid=2892»