ArcGIS Pro 3.0 API Reference Guide
ArcGIS.Core.Geometry Namespace / ProjectionTransformation Class / InputSpatialReference Property

InputSpatialReference Property (ProjectionTransformation)
Gets the input spatial reference.
Syntax
public SpatialReference InputSpatialReference {get;}
Requirements

Target Platforms: Windows 11, Windows 10, Windows 8.1

ArcGIS Pro version: 2.0 or higher.
See Also