来自RichTextBox的c# WPF行和列号。

I'm porting an application from WinForms to WPF and I've hit a snag while trying to get the line and column number for where the selection is in the text box. I was able to do it quite simply in WinForms but WPF has a completely different way of implementing a RichTextBox so I have no idea how to go about it.I'm porting an application from WinForms to WPF