ArcGIS Pro 2.8 API Reference Guide
FindLayoutPanes Method
Example 

ArcGIS.Desktop.Core Namespace > LayoutFrameworkExtender Class : FindLayoutPanes Method
Does not need to be specified.
Layout
Find the layout panes that reference a specific layout.
Syntax
Public Shared Function FindLayoutPanes( _
   ByVal paneCollection As PaneCollection, _
   Optional ByVal layout As Layout _
) As IEnumerable(Of ILayoutPane)

Parameters

paneCollection
Does not need to be specified.
layout
Layout

Return Value

Example
//Find and close all layout panes associated with a specific layout.

LayoutProjectItem findLytItem = Project.Current.GetItems<LayoutProjectItem>().FirstOrDefault(item => item.Name.Equals("Layout"));
Layout findLyt = await QueuedTask.Run(() => findLytItem.GetLayout());  //Perform on the worker thread

var panes = ProApp.Panes.FindLayoutPanes(findLyt);
foreach (Pane pane in panes)
{
  ProApp.Panes.CloseLayoutPanes(findLyt.URI);  //Close the pane
}
Requirements

Target Platforms: Windows 10, Windows 8.1

See Also

Reference

LayoutFrameworkExtender Class
LayoutFrameworkExtender Members