ArcGIS Pro 2.6 API Reference Guide
OnAddToProject Method (IProjectItem)

ArcGIS.Desktop.Core Namespace > IProjectItem Interface : OnAddToProject Method
Callback whenever a project item has been added to a project
Syntax
void OnAddToProject()
Sub OnAddToProject() 
Remarks
Also called whenever a "remove project item" operation is undone
Requirements

Target Platforms: Windows 10, Windows 8.1, Windows 7

See Also

Reference

IProjectItem Interface
IProjectItem Members