public void MoveSubElement(Form form)
{
    if (form.ProfileCount > 0)
    {
        int profileIndex = 0;   // get first profile
        ReferenceArray ra = form.get_CurveLoopReferencesOnProfile(profileIndex, 0);
        foreach (Reference r in ra)
        {
            ReferenceArray ra2 = form.GetControlPoints(r);
            foreach (Reference r2 in ra2)
            {
                Point vertex = document.GetElement(r2).GetGeometryObjectFromReference(r2) as Point;

                XYZ offset = new XYZ(0, 15, 0);
                form.MoveSubElement(r2, offset);
                break;  // just move the first point
            }
        }
    }
}

Public Sub MoveSubElement(form As Form)
    If form.ProfileCount > 0 Then
        Dim profileIndex As Integer = 0
        ' get first profile
        Dim ra As ReferenceArray = form.CurveLoopReferencesOnProfile(profileIndex, 0)
        For Each r As Reference In ra
            Dim ra2 As ReferenceArray = form.GetControlPoints(r)
            For Each r2 As Reference In ra2
                Dim vertex As Point = TryCast(document.GetElement(r2).GetGeometryObjectFromReference(r2), Point)

                Dim offset As New XYZ(0, 15, 0)
                form.MoveSubElement(r2, offset)
                    ' just move the first point
                Exit For
            Next
        Next
    End If
End Sub