Unknown server tag 'asp:ListView'. sharepoint

Error
Unknown server tag 'asp:ListView'.

Troubleshoot issues with Microsoft SharePoint Foundation.

Correlation ID: 550b12f2-1d78-432c-94f0-0d4bffa54c0b

Date and Time: 7/7/2012 11:34:29 PM

修改web。config，加入下面controls中的内容

<pages>

 <controls>
        <add tagPrefix="asp" namespace="System.Web.UI" assembly="System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" />
        <add tagPrefix="asp" namespace="System.Web.UI.WebControls" assembly="System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>

      </controls>

</pages>