Implement ICommandSource Sample in VB

The C# ICommandSource SDK Sample works.

But if I try to implement the ICommandSource Interface into ab VB Project
(Based in the C# sample) I can't make it running

If I add a ReadOnly Property I can't set it in XAML
and If I change it to Read/Writable the compiler is not happy:
"Class 'CommandItem' must implement 'ReadOnly Property Command() As
ICommand' for interface 'System.Windows.Input.ICommandSource'. Implementing
property must have matching 'ReadOnly' or 'WriteOnly' specifiers."

Who can give me a running VB-Sample?

Horst