OnPropertyChangedstring

OnPropertyChan... is a term used in documentation and code to denote a hook or callback that is invoked when a property's value changes. The name suggests a variant of the classic OnPropertyChanged pattern, with the addition that change notifications may be delivered through a channel or message-passing mechanism to observers. While not a formal standard, it appears in discussions of data-binding and reactive programming as a way to decouple property updates from their consumers.

The primary purpose of a mechanism like OnPropertyChan... is to notify interested parties that a value has changed, enabling UI updates, data binding, validation, and synchronization across components. By exposing a dedicated change notification method, developers can centralize logic for what happens after a property changes, such as raising events, enqueueing messages, or dispatching work to a specific thread or context.

Common design patterns associate OnPropertyChan... with patterns such as the Model-View-ViewModel (MVVM) or observer-based architectures. In languages that support channels or message queues, the notification can be sent through a channel to multiple subscribers, helping to decouple publishers from listeners and improve testability. Typical method signatures resemble those of OnPropertyChanged-style callbacks, often taking the property name and, in more elaborate variants, the old and new values.

Practical considerations include ensuring notifications are thread-safe, avoiding unnecessary updates by checking value equality before invoking, and delivering notifications on the appropriate context (for example, the UI thread when updating the interface). Understanding the specific framework conventions is important, as implementations and conventions for OnPropertyChan... vary across environments.