HOW TOSolve the “CS0104: 'MenuItem' is an ambiguous reference between 'System.Web.UI.WebControls.MenuItem' and 'Telerik.WebControls.MenuItem' in VS2005” error message
Since Microsoft introduced a free menu component inside ASP.NET 2.0, it obviously conflicts with RadMenu’s MenuItem class. In view of the fact that Microsoft’s MenuItem class is built-in the framework backend it takes priority in the class resolution process. Hence when you define the RadMenu’s MenuItem class without a fully-qualified name, the compiler resolves the declaration in favor of the built-in menu component. In other words it tries to compile System.Web.UI.WebControls.MenuItem instead of Telerik.WebControls.MenuItem.
A possible workaround at the moment is to define RadMenu’s MenuItem class with its fully-qualified name - Telerik.WebControls.MenuItem.
A complete solution to the problem would be changing the name of our MenuItem class. We will consider this for the most recent menu release.