How to determine if Box2D fixture or shape is solid?

I think it is very simple to do but somehow I cannot find the way to do it. I want to draw selected fixtures and I don't really know if they should be filled or not - there is nothing like Fixture.IsSolid or Shape.IsSolid.

I actually do it in Farseer, but it is only Box2D for C# actually.

EDIT: I've checked Farseer examples for this and it seems they just assume all are solids. They certainly do not have to be..

Solution

I don't know much about Farseer, but in Box2D polygons and circle shapes will always be solid, while chain and edge shapes are not solid.