Curve parameter as an Input

dear all,

I'm new in GH.

I'm developing a plug in and I need to use a Curve as an input in one of the nodes. Its necessary to be any type of curve. polyline, line, bspline, etc.

as a register input parameter I have this, think is ok.

pManager.AddCurveParameter("bla bla", "bla", "bla of bla bla", GH_ParamAccess.item);

in the Solve Instance()

I tried this:

Curve crv = new Curve(); //but I have an error: is inaccessible due to its protection

level.

So how can I manage all the curve types as, for example, the node Curve does?

any clue will be appreciated.

thanks in advance.

c