Do you have more info?
I am not too familiar with WPF; but I would guess that, just in the case of WinForms, you'll have to determine the corresponding Teststack.White control; and consider "wrapping" it - depending on the degree of customization of said control.
Which utility, if any, are you using to identify the control types? I use Inspect.exe
"C:\Program Files (x86)\Windows Kits\10\bin\10.0.16299.0\x64\inspect.exe"