ArcGIS Pro 2.8 API Reference Guide
PlugIn Class
Members 

ArcGIS.Desktop.Framework.Contracts Namespace : PlugIn Class
Represents the base class for most framework commands including Button and Tool. This is an abstract class.
Syntax
Inheritance Hierarchy

System.Object
   ArcGIS.Desktop.Framework.Contracts.PropertyChangedBase
      ArcGIS.Desktop.Framework.Contracts.PlugIn
         ArcGIS.Desktop.Framework.Contracts.Button
         ArcGIS.Desktop.Framework.Contracts.ComboBox
         ArcGIS.Desktop.Framework.Contracts.CustomControl
         ArcGIS.Desktop.Framework.Contracts.DynamicMenu
         ArcGIS.Desktop.Framework.Contracts.EditBox
         ArcGIS.Desktop.Framework.Contracts.Gallery
         ArcGIS.Desktop.Framework.Contracts.PaneBase
         ArcGIS.Desktop.Framework.Contracts.Spinner

Requirements

Target Platforms: Windows 10, Windows 8.1

See Also

Reference

PlugIn Members
ArcGIS.Desktop.Framework.Contracts Namespace