Element 'Preview' is not a known element. as tagname

Question

Hi,

<uct:Preview ID="previewID" runat="server" pPath="" />


In the above line the TagName "Preview" has green underline with warning

"Element 'Preview' is not a known element. This can occur if there is a compilation error in the Web site, or the web.config file is missing".

I have deleted the ReflectedSchema folder, re-opened the VS and the issue is still there.

This is not a massive issue on it own however it is affecting me to modify the control attribute from the code file because the control ID is not recognised, as follows

previewID.Attribute["pPath"] = pIPath;

and i am getting "The name previewID does not exist in the current context".

Thanks for your help.