In XAML, how do you use a namespace prefix in a property element syntax?

Hello,

I need to use a PasswordBox in MVVM, but since PasswordBox's Password property isn't a dependency property, and can't be bound to a property in the ViewModel, I went searching and found a nice attached property (by Pete O'Hanlon).  I was easily able to get it to work, by adding an attribute to the <PasswordBox> element:

<PasswordBox
	Lib:BoundPasswordBox.BoundPassword="{Binding Path=Password, UpdateSourceTrigger=PropertyChanged}"
	...

Next, I need to add validation, so I tried turning it into a property element instead, but I can't figure out the syntax for the namespace prefix (Lib:):

<PasswordBox
	... ><PasswordBox.Lib:BoundPasswordBox.BoundPassword><Binding
			Path="Password"
			UpdateSourceTrigger="PropertyChanged"><Binding.ValidationRules>
...

So, what's the syntax for an attached property with a namespace prefix in a property element?

Thanks

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