ArcGIS Pro 2.7 API Reference Guide
Contents Class
Members  Example 

ArcGIS.Desktop.Core Namespace : Contents Class
IContentsProviders will return an instance of this class for their "contents". Contents are shown in the Contents Dock pane when the IContentsProvider is activated.
Object Model
Contents ClassOperationManager Class
Syntax
public class Contents 
Public Class Contents 
Remarks
Typically:
The ContentsView is your user control or "UI"
The ContentsViewModel is the UI view model and should be your pane (it is usually also the IContentsProvider)
The OperationManager is the operation manager you want to contain Undo/Redo operations when your content is active. For example: see the code snipped below. Your pane has been activated and is being asked to provide its Contents via IContentsProvider.Contents
Example
internal class MyCustomPaneViewModel : ViewStatePane, IContentsProvider, IContentsControl {
    ...
    private Contents _contents;
    
    public Contents Contents  {
       get {
      if (_contents == null) {
        
        //Instantiate your UI (probably a custom user control)
        FrameworkElement contentsControl = new MyCustomPaneContentsUserControl();
        contentsControl.DataContext = this;//set the View model to the data context (standard MVVM)
 
        //Make the ArcGIS.Desktop.Core.Contents control which is used
        //by the contents dockpane to show your pane's content
        _contents = new Contents();
        _contents.ContentsView = contentsControl;//Your UI
        _contents.ContentsViewModel = this;//used for IContentsControl, IContentsPaneClipboardOps and INotifyPropertyChanged
        _contents.OperationManager = this.OperationManager;//Your operations manager
     }
     return _contents;
   }
}
Inheritance Hierarchy

System.Object
   ArcGIS.Desktop.Core.Contents

Requirements

Target Platforms: Windows 10, Windows 8.1

See Also

Reference

Contents Members
ArcGIS.Desktop.Core Namespace