Print WPF Visuals with MVVM pattern

Question

My ViewModel has a PrintCommand executing a Method called PrintCalendar(). But the Calendar aka datagrid is in the View, so how do I get my datagrid into the ViewModel?

Getting my hands dirty and do all that stuff in code-behind? oh no...

PrintDialog printDlg = new PrintDialog();
printDlg.PrintVisual(datagrid, "Grid Printing.");