How do you add a 'public partial class ThisWorkbook' to a VSTO application in C#? - vsto

Question

I am trying to add an ActionPane to an Excel VSTO Add-in. I need to access the ThisWorkbook.ActionsPane collection to add my action panes.
The Microsoft documentation at:
https://learn.microsoft.com/en-us/visualstudio/vsto/how-to-add-an-actions-pane-to-word-documents-or-excel-workbooks?view=vs-2019
says:
To show the actions pane, add the user control to the Controls
property of the ThisDocument.ActionsPane field (Word) or
ThisWorkbook.ActionsPane field (Excel).
Add the following code to the ThisDocument or ThisWorkbook class as a
class-level declaration (do not add this code to a method).
This implies that I need to add a ThisWorkbook class to the VSTO solution. My questions are:
What base class contains the ActionsPlane collection?
How would I add a class derived from this base class to my VSTO?
Some on-line examples of a ThisWorkbook class contain regions that are designer generated.
My workload includes every VSTO item available. There are no Excel items at all under 'Add New Item' or 'Add New User Control' in Visual Studio 2019. Beyond the Ribbon Bar, there are no designers for VSTO.
The only way that I see to do this is to add a ThisWorkbook class manually.
Am I correct in saying that any designers that may have existed in previous versions of Visual Studio, no longer exist in Visual Studio 2019?

Answer 1

You need to differentiate document-level and application-level add-ins.
An actions pane is a customizable Document Actions task pane that is attached to a specific Microsoft Office Word document or Microsoft Office Excel workbook. The actions pane is hosted inside the Office task pane along with other built-in task panes, such as the XML Source task pane in Excel or the Styles and Formatting task pane in Word. You can use Windows Forms controls or WPF controls to design the actions pane user interface.
Read more about Actions panes in the How to: Add an Actions Pane to Word Documents or Excel Workbooks article if you are developing a document-level add-in.
If you are developing an application-level add-in you may be interested in using Custom task panes. Task panes are user interface panels that are typically docked to one side of a window in a Microsoft Office application. Custom task panes give you a way to create your own task pane and provide users with a familiar interface to access your solution's features. For example, the interface can contain controls that run code to modify documents or display data from a data source. See Walkthrough: Automate an application from a custom task pane to get started quickly.