Why the curves are not shown in rhino

Hi guys,

Here is my codes snippet:

    protected override void RegisterOutputParams(GH_Component.GH_OutputParamManager pManager)
        pManager.AddCurveParameter("Unfolded Contours", "Cs", "Sheet Metal Model unfolded contours", GH_ParamAccess.list);
        pManager.AddTextParameter("Bending Direction", "BDs", "Bending Directions", GH_ParamAccess.list);

    protected override void SolveInstance(IGH_DataAccess DA)
        var curves = new Rhino.Runtime.InteropWrappers.SimpleArrayCurvePointer();
		... c++ function generate the curve 99 curves. ...
        Curve[] contours = curves.ToNonConstArray();
        bool chk = contours[0].IsValid;   // the curve is valid, it is a curve line. 
        bool st = DA.SetDataList(0, contours);

the return value st is “true”.

But no curves are displayed in rhino, could anyone please tell me which direction I should go? I ask chatgpt, its solution doesn’t work either.

thank you.