Problem of ReportViewer 2010 on aspx page

I have installed ReportViewer and added reference so my web.config has these

    <add assembly="Microsoft.ReportViewer.Common, Version=10.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/>
        <add assembly="Microsoft.ReportViewer.WebForms, Version=10.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/>
        <add assembly="System.Web.DataVisualization, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>

I have already have these dll in

C:\Program Files\Microsoft Visual Studio 10.0\Common7\IDE\PublicAssemblies:-

Microsoft.ReportViewer.Common.dll
Microsoft.ReportViewer.WebForms.dll
System.Web.DataVisualization.dll

However when I drag and drop the reportviewer onto the page, in design view, it says

Error Creating Control: Failed to create designer 'Microsoft.Reporting.WebForms.ReportViewer.... etc'

What am I missing ? Thanks