When is the OnParametersChanged event triggered on a block?

The OnParametersChanged event is specifically designed to respond to changes in the parameters of a block. This event is triggered when the values of parameters passed from the parent screen or block are modified. This mechanism allows developers to adjust the block's internal logic or UI in reaction to the new parameter values, ensuring that the block reflects the updated data appropriately.

When a new value is assigned to a parameter in the parent, the OnParametersChanged event provides an opportunity to execute any necessary updates or adjustments in the block. This is fundamentally significant in building interactive applications that rely on real-time data flow between components.

The other options do not represent scenarios where OnParametersChanged would be triggered. For instance, simply creating a new block wouldn't invoke changes in parameter values, nor would the initial loading of a block lead to this event being fired. Additionally, refreshing a screen may not necessarily change the parameter values being passed, which is the specific trigger for this event. All of these points highlight the unique nature of the OnParametersChanged event in maintaining the integrity and responsiveness of component interactions in OutSystems applications.