ArcGIS Pro 3.0 API Reference Guide
ArcGIS.Core.Geometry Namespace / Envelope Class / Extent Property

Extent Property (Envelope)
Gets the minimum enclosing envelope of this instance. Returns null if this geometry has IsEmpty = true.
Syntax
public override Envelope Extent {get;}
Requirements

Target Platforms: Windows 11, Windows 10, Windows 8.1

ArcGIS Pro version: 2.0 or higher.
See Also