Bodies in Farseer have no "shape" of their own. The Body defines the position, velocity, mass, etc (basically a point-mass). Fixtures give that body a "shape" that can collide with things.
You can get the AABB (axis-aligned bounding-box) of a Fixture with
Fixture.Shape.ComputeAABB(...). Don't use
Fixture.GetAABB, which is a "loose" AABB used by Farseer for collision detection.
(Note that the
LoopShape can have multiple child shapes, see
Fixture.Shape.ChildCount. For other shapes just use
childIndex = 0.)
Depending on your needs, you might want to get the AABB of the transformed Fixture. For example, to get the AABB in world space, use the transform from
Body.GetTransform(...). Otherwise use:
Transform t = new Transform();
Note that a Body can have multiple Fixtures (
Body.FixtureList). If this is the case, you will want to combine the AABBs of each Fixture using
If you want to guarantee that the resulting width and height are equal to something you set-up at object-creation time, you may want to just use the
Body.UserData field to store that information.