Base class includes the field 'X', but its type (System.Web.UI.ScriptManager) is not compatible with the type of control (System.Web.UI.ScriptManager)

Question

The full error is

The base class includes the field \'ScriptManager1\', but its type (System.Web.UI.ScriptManager) is not compatible with the type of

Answer 1

I managed to fix it by adding this to web.config:

I believe it forces the .net runtime to use the new versions of those assemblies.