ArcGIS Pro 2.9 API Reference Guide
IMappableItemEx Interface
Members 

ArcGIS.Desktop.Mapping Namespace : IMappableItemEx Interface
Implemented by items that can be added to a map. Use this in conjuction with IMappableItem.
Syntax
public interface IMappableItemEx 
Public Interface IMappableItemEx 
Remarks
The methods in IMappableItemEx differ from those in IMappableItem by their return values. Use the IMappableItemEx methods to ensure that calling code is able to correctly detect the data added by the item if required.
Requirements

Target Platforms: Windows 11, Windows 10, Windows 8.1

See Also

Reference

IMappableItemEx Members
ArcGIS.Desktop.Mapping Namespace