Adding a picker in XAML

I'd like to add a picker control that has the values 1,2,3,4,5.

I tried the following...

        <Picker SelectedIndex="{Binding NewCriterion.Importance}" >
            <Items>
                <x:String>"1"</x:String> 
                <x:String>"2"</x:String>
            </Items>
        </Picker> 

to no avail. The documentation is a bit sparse on how to do this in XAML. Help?