Hi SK,
First you need to create MapViewInteractionOptions() instance and set the navigation property as below:
// code based
var interactions = new MapViewInteractionOptions() ;
interactions.IsZoomEnabled = false;
MyMapView.InteractionOptions = interactions;
OR
If you would like to do through XAML, you could create the instance in XAML :
<esri:MapView x:Name="MyMapView">
<esri:MapView.InteractionOptions>
<esri:MapViewInteractionOptions IsZoomEnabled = false/>
</esri:MapView.InteractionOptions>
</esri:MapView>
Hope that helps.
Nagma