What resource would you recommend for learning how to develop wpf custom controls?

Question

.NET

I want to learn how to develop custom controls for WPF.
Advise information resources or literature, it is possible in English,
about the creation of such controls.
Okay, if you create simple ones. This I can.
But my goal is to create controls like multicombobox, pivotdatagrid.
As I understand it, to create such controls, you need to inherit from multiselector, but I don’t know how to
work with it normally.
I'm most interested in how the datagrid works so that I can create additional functionality for it.
Advise information resources on this topic.