Localization for Validation property

As per this thread https://world.episerver.com/forum/developer-forum/Developer-to-developer/Thread-Container/2015/8/localized-property-name-in-validation/ we can fetch localized validation property display name by casting it to PageData type. But we have this limitation set to BlockData, ContentData Block types. How can we update this line of code for specific block type within content area?

var propertyDefinitionId = ((PageData) validationContext.ObjectInstance).Property[propertyName].PropertyDefinitionID;