In which situation is the On Parameters Changed Event triggered?

The On Parameters Changed Event is triggered specifically when the block's parent modifies the value of one or more input parameters of that block. This event is essential for handling scenarios where the input that a block has received is updated, allowing the block to react accordingly to changes and refresh its internal state or update its output based on the new input values.

In this context, changing the value at the parent level indicates that the block should re-evaluate how it operates based on the new data. This is crucial in environments like OutSystems, where dynamic data binding between elements is vital for user experience and functional responsiveness in applications.

The other contexts mentioned do not align with how the event is intended to function. For instance, if the value changes within an action of the block's client, it does not inherently reflect a change that is observable from the parent perspective, which is necessary for the On Parameters Changed Event to trigger. Similarly, the event isn't explicitly triggered by the parent unless a parameter change occurs, nor does it occur simply by executing a block’s action without actual changes to parameters. Therefore, the scenario where the parent changes the value of at least one input parameter is the precise condition under which this event is activated.