Assembly: PresentationFramework (in PresentationFramework.dll)
You can set validation rules on both the MultiBinding object and the individual Binding objects in the MultiBinding object. The binding engine evaluates the ValidationRules on the MultiBinding object when a value moves from the binding target property to the IMultiValueConverter object (multi-value converter). After that, when a value moves from the converter to the binding source property of an individual binding, the binding engine evaluates the ValidationRules on that Binding object.
Available since 3.0