Occurs when the Appearance Controller collects the appearance rules and determines whether or not the specific IAppearanceRuleProperties object is empty.
The CustomGetIsRulePropertiesEmpty event's data class is DevExpress.ExpressApp.ConditionalAppearance.CustomGetIsRulePropertiesEmptyEventArgs.
By default, the IAppearance.FontStyle, IAppearance.FontColor, IAppearance.BackColor, IAppearance.Visibility and IAppearance.Enabled nullable properties of the IAppearanceRuleProperties object are checked for a value presence and a rule properties object is considered empty if there are no values found. Once a rule properties object is considered empty, it is excluded from the processing list and is not processed at all. The result is cached to avoid duplicated calculations. Handle the CustomGetIsRulePropertiesEmpty event in case you have introduced new properties and want to manually manage their values.