Top-level windows forms control cannot be exposed as an activex control
Activex control in windows form.
How to create activex control in visual studio 2019
How to: Add ActiveX Controls to Windows Forms
While the Windows Forms Designer in Visual Studio is optimized to host Windows Forms controls, you can also put ActiveX controls on Windows Forms.
Caution
There are performance limitations for Windows Forms when ActiveX controls are added to them.
Before you add ActiveX controls to your form, you must add them to the Toolbox.
For more information, see COM Components, Customize Toolbox Dialog Box.
Add an ActiveX control to your Windows Form
To add an ActiveX control to your Windows Form, double-click the control on the Toolbox.
Visual Studio adds all references to the control in your project.
For more information about things to keep in mind when using ActiveX controls on Windows Forms, see Considerations When Hosting an ActiveX Control on a Windows Form.
Note
The Windows Forms ActiveX Control Importer (AxImp.exe) creates event arguments of a different type than expected upon importation of ActiveX dynamic link libraries.
The arguments created by AxImp.exe are similar to the following: , when is expected. Be aware that this