Line of effect for Dispel Magic?

[Magus Coeruleus]

Do you need a line of effect for Dispel Magic? Let's say you want to target an area for dispelling that lies behind a glass wall. You can clearly see the area you want to dispel, but there is that wall between you. Can you do it?

 

[Doorf]

Normaly you can't cat spell through anything that blocks like of effect.
So no you can't dispel,counter spell behind wall of force, glass, stone etc. You can't even dispel anything behind dispeling screen.