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've run into this issue when upgrading a web application from .NET 2.0 to 3.5.

Check your web.config is correctly set for .NET 3.5. I added/changed the following: