Raised when an action availability changes.
Assembly: Microsoft.Lync.Model (in Microsoft.Lync.Model.dll)
When you want to be advised that an action to be taken is on a single participant modality instead of the conversation modality, register for this event on Participant.Modalities[ModalityType]. For example, if the availability of a controller action changes on a conversation participant's ApplicationSharingModality, you get the event if you have registered for it on the modality at Participant.Modalities[ModalityType.ApplicationSharing]. Note: You must always register for this event on the conversation Modality in addition to event registration on any participant's modalty.