User Data lost during conversion

Hi,

I develop a new component library with C# and get a mess with user data mechanism.

My issue is the following :

* a component A generates a list of polylines as output and user data are associated to each segment of the polyline like this:

solveinstance() method of A :

----------------------------

for (int i = ....) // a loop 

{

r = new Polyline(...); // polyline initiated

r.SegmentAt(0).ToNurbsCurve().SetUserString("power", 1.0)

outputList.add(r)

}

DA.SetDataList(outputList)

When using this output in my other component B as an input, I hoped retrieving my user data (here "power" set to 1.0). But no !

I am actually doing in the solveInstance() method of B a cast from Curve to Polyline to avoid a "Invalid Cast Curve>>Polyline" issue in Grasshopper :

List<Curve> input = new List<Curve>();
DA.GetDataList<Curve>(0, input);
List<Polyline> output = new List<Polyline>(input.Count);
Polyline ply;
foreach (Curve c in input)
{
c.TryGetPolyline(out ply);
output.Add(ply);
Rhino.RhinoApp.WriteLine(ply.SegmentAt(0).ToNurbsCurve().GetUserString("power"));
}

But the WriteLine should display at Rhino prompt the value "1.0" no ? nothing is displayed, as if it was lost during the conversion.

Anybody could help ? Where am I wrong ?