Create instance of user control to another user control via

Question

Goal:
After clicking on the Kassa button from the user control usercontrol_menu, the user control usercontrol_kassa shall be displayed in the mainwindows.

Problem:
I have difficult to find a correct source code to implement it. The closest source code is located below.

A suggestion is to retrieve the instance of main window and then create a new instance of usercontrol_kassa inside of usercontrol_menu's button Kassa.

 

I also believe that you need to use frame control (http://www.mindstick.com/Articles/f3ab29d9-8e26-4b01-a0b8-5b41521f9bfc/?Frame%20control%20in%20WPF) but I don't know how to use it in this context.

Information:
- usercontrol_menu is menu with three buttons.
- The main windows will contain totally two user control (usercontrol_menu and usercontrol_kassa).
- After you have click the Kassa button you should enable to create a new instance of usercontrol_kassa and it should be displayed inside of mainwindows.
- main Windows, usercontrol_menu and usercontrol_kassa has¨their own project in VS 2013.