Namespace TestNs
    Public Class TestCls
        Inherits Windows.Forms.TextBox
 
    End Class
End Namespace
 
Public Class Form1
    Inherits System.Windows.Forms.Form
 
#Region " Vom Windows Form Designer generierter Code "
...
#End Region
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles MyBase.Load
 
    End Sub
End Class
 
Namespace TestNs2
    Public Class TestCls2
        Inherits Windows.Forms.TextBox
 
    End Class
End Namespace