Unknown server tag 'asp:ListView' error with Sharepoint 2010 / .Net 3.5

Question

I'm developing a visual web part in Visual Studio 2010 for sharepoint and i have a listview control embedded.

I keep getting this error message in runtime even though I made sure it's namespaces are included and everything in the right place.

any ideas?

Answer 1

Made sure the build setting is 3.5 and not 3.5 Client Profile?

Answer 2

I read some threads talking about a bug in .net 3.5 and that we need to reinstall the SP1 to solve the problem, while I found this time-savy solution by simply adding a line to web.config:

inside the tag:

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

Good luck