check for curve type C#?

Any wizards out there able to help me with this?  It may very well be a stupid question but my brain isn't working so well at the moment.

I'm trying to write some code that checks which type of curve is coming into a component.  (arc, linecurve, nurbscurve, etc)

Here's what I have:

public Grasshopper.Kernel.Data.GH_Structure<Grasshopper.Kernel.Types.GH_Curve> _curveTree;

//loop through branches

for (int i = 0; i < _curveTree.Branches.Count; i++)

            {

                //The path

                Grasshopper.Kernel.Data.GH_Path path = _curveTree.Paths[i];

                //loop through list

                for (int j = 0; j < _curveTree.Branches[i].Count; j++)

                {

                    GH_Curve gCurve = _curveTree[path][j];

                 //check for curve type here - HOW?

                }

            }

Any help appreciated, thanks!