The following code works well in a VB.NET application:

Namespace My

    Partial Class MyApplication

        Inherits Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase

        Private Sub App_Startup(ByVal sender As Object, ByVal e As Microsoft.VisualBasic.ApplicationServices.StartupEventArgs) Handles Me.Startup
            Framework.App.Initialize()
            MessageBox.Show("Initialize")
        End Sub

    End Class

End Namespace

However, I need to put that code in a DLL, which is a custom framework. But, this is not accepted because I obtain the following message at design time:

Base class 'Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase' specified for class 'MyApplication' cannot be different from the base class 'Microsoft.VisualBasic.ApplicationServices.ApplicationBase' of one of its other partial types.

It is the same code. So, why this doesn't work in the DLL?