Drawing Line on Canvas

All:

OK - I know this seems like a ridiculously simply question, but I
cannot find an answer. In the "old days" of Windows programming (the
old days include .NET 2.0 Forms), one could somehow obtain a graphics
context, e.g., CreateGraphics() and draw on a form, etc.

How do you do the same thing in WPF (Windows Presentation Foundation)?
I am simply trying to draw (render) a line on a Canvas - that's it.

There does seem to be an equivalent of CreateGraphics() or GetDC() or
GetDrawingContext() - or anything one would naturally assume to be
present in an API of this type.

Examples?

Thank you,
jpuopolo