HttpResponse.AddCacheItemDependency Method
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Makes the validity of a cached response dependent on another item in the cache.
Namespace: System.Web
Assembly: System.Web (in System.Web.dll)
The following example is an ASP.NET user control that is output cached. The code for the control calls the AddCacheItemDependency method with the key of an item stored in the Cache object passed as its parameter. If the item does not exist in the cache, the control's response that was stored in the output cache is invalidated. This means that on the subsequent request, a new version of the control's response will be added to the output cache.
Next, the code checks whether an item associated with a bookData key is stored in the Cache object, and displays one of two lines of text dependent upon the result. Then, the code sets the DataSource property of a DataGrid control, which is named dgBooks, with a call to a custom DataHelper class's shared GetBookData method, and populates the DataGrid with the DataBind method.
<%@ Control Language="c#" %>
<%@ Outputcache duration="10" varybyparam="none" shared="True" %>
<%@ Import Namespace = "Samples.AspNet.CS" %>
<%@ Import Namespace = "System.Data" %>
<script runat="server">
private void Page_Load(object sender, System.EventArgs e)
{
// Make user control invalid if the
// cache item changes or expires.
Response.AddCacheItemDependency("bookData");
// Create a DataView object.
DataView source = (DataView)Cache["bookData"];
// Check if the view is stored in the cache
// and generate the right label text
// dependent upon what is returned.
if (source == null)
{
source = DataHelper.GetBookData();
lblCacheMsg.Text = "Data generated explicitly.";
}
else
{
lblCacheMsg.Text = "Data retrieved from application cache.";
}
dgBooks.DataSource = source;
dgBooks.DataBind();
lblOutputMessage.Text = DateTime.Now.ToString();
}
</script>
<table>
<tbody>
<tr>
<th>
Books</th>
<td>
</td>
</tr>
<tr>
<td>
<asp:DataGrid id="dgBooks" runat="server"></asp:DataGrid>
</td>
<td>
</td>
</tr>
<tr>
<td>
<asp:Label id="lblCacheMsg" runat="server"></asp:Label>
</td>
<td>
</td>
</tr>
<tr>
<td>
The control was created at:
</td>
<td>
<asp:Label id="lblOutputMessage" runat="server"></asp:Label>
</td>
</tr>
</tbody>
</table>
Windows 8 Release Preview, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 SP2, Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
