ValidationRule To Enforce Unique Name

class YourCollectionType : DependencyObject {

    [PROPERTY DEPENDENCY OF ObservableCollection<YourType> NAMED: BoundList]

}

YourCollectionType ListToCheck { get; set; }

<Binding.ValidationRules>
    <YourValidationRule>
       <YourValidationRule.ListToCheck>
          <YourCollectionType BoundList="{Binding Path=TheCollectionYouWantToCheck}" />
       </YourValidationRule.ListToCheck>
    </YourValidationRule>
</Binding.ValidationRules>