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Object Caching Item Dependency

<%@ Page Language="C#" AutoEventWireup="true"  CodeFile="Default.aspx.cs"  Inherits="Default_aspx" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" > <head runat="server">     <title>Object Caching</title> </head> <body>     <form id="form1" runat="server">     <div>     <h1>Object Caching</h1>     <h2>Item Dependency</h2>      <asp:Label ID="lblMessage" runat="server" />      <br />      <asp:GridView ID="gv" runat="server" />      <br />      <asp:Button ID="btnClear" runat="server" Text="Clear Cache" OnClick="btnClear_Click" />      <asp:Button ID="btnPost" runat="server" Text="Post" />      <br />      <asp:Button ID="btnInit" runat="server" Text="Initialize Keys" OnClick="btnInit_Click" />      <asp:Button ID="btnKey0" runat="server" Text="Change Key 0" OnClick="btnKey0_Click" />     </div>     </form> </body> </html> File: Default.aspx.cs using System; using System.Data; using System.Configuration; using System.Web; using System.Web.Security; using System.Web.UI; using System.Web.UI.WebControls; using System.Web.UI.WebControls.WebParts; using System.Web.UI.HtmlControls; using System.Web.Caching;      //  necessary for CacheDependency using System.Xml;            //  necessary for Xml stuff public partial class Default_aspx : System.Web.UI.Page  {     protected void Page_Load(object sender, EventArgs e)     {      CreateGridView();    }    private void CreateGridView()    {      DataSet dsGrid;      dsGrid = (DataSet)Cache["GridViewDataSet"];      if (dsGrid == null)      {        dsGrid = GetDataSet();        string[] fileDependsArray = {Server.MapPath("Data.xml")};        string[] cacheDependsArray = {"Depend0", "Depend1", "Depend2"};        CacheDependency cacheDepends = new CacheDependency                       (fileDependsArray, cacheDependsArray);        Cache.Insert("GridViewDataSet", dsGrid, cacheDepends);        lblMessage.Text = "Data from XML file.";      }      else      {        lblMessage.Text = "Data from cache.";      }      gv.DataSource = dsGrid.Tables[0];      gv.DataBind();    }    private DataSet GetDataSet()    {      DataSet dsData = new DataSet();      XmlDataDocument doc = new XmlDataDocument();      doc.DataSet.ReadXml(Server.MapPath("Data.xml"));      dsData = doc.DataSet;      return dsData;    }   protected void btnClear_Click(object sender, EventArgs e)    {       Cache.Remove("GridViewDataSet");     CreateGridView();    }   protected void btnInit_Click(object sender, EventArgs e)   {     Cache["Depend0"] = "This is the first dependency.";     Cache["Depend1"] = "This is the 2nd dependency.";     Cache["Depend2"] = "This is the 3rd dependency.";   }   protected void btnKey0_Click(object sender, EventArgs e)   {     Cache["Depend0"] = "This is a changed first dependency.";   } }   File: NorthWind.xml <?xml version="1.0" encoding="UTF-16" ?> <ROOT>   <Customers CustomerID="A" CompanyName="A" ContactName="Dan" ContactTitle="Sales" Address="Str. 57" City="Berlin" PostalCode="11111" Country="Germany" Phone="030-0074321" Fax="030-0076545" />    <Customers CustomerID="B" CompanyName="B" ContactName="Ana" ContactTitle="Owner" Address="Road 22" City="New York" PostalCode="00000" Country="Mexico" Phone="(555) 555-4729" Fax="(5) 555-3745" />  </ROOT>