LwPolyline is always closed, Polyline2d.Vertices cannot set Bulge, and Dxf opening in CAD Error

I tried to create some polylines into a dxf file with the given file path. Because IsClosed defined with IPolyline was readonly, I used LwPolylineFlags to set the LwPolyline closed. However, after trying three options of them, none of them is opened polyline. Please, have a look at the first function. Secondly, I created a polyline2D with setting Bulge at one of its vertices. The arc cannot be set up with it. Both bugs, I've checked in debugs mode, were correct, while in the AutoCAD they didn't match my setting. Besides, whenever I opened the dxf file. AutoCAD always opened the file twice and showed it was readonly. Was it correct? //Program 1 public static void DrawLwPolylineTest(string input) { CadDocument doc = new CadDocument();

        List<LwPolyline.Vertex> vertices = new List<LwPolyline.Vertex>() {
            new LwPolyline.Vertex(new XY(0,0)),
        new LwPolyline.Vertex(new XY(1,0)),
        new LwPolyline.Vertex(new XY(2,1)),
        new LwPolyline.Vertex(new XY(3,1)),
        new LwPolyline.Vertex(new XY(4,4))
        };

        var LwPline = new LwPolyline();

        for (int i = 0; i < vertices.Count; i++)
            LwPline.Vertices.Add(vertices[i]);
        LwPline.Flags = LwPolylineFlags.Default;

        LwPline.Vertices[2].Bulge = -0.5;
        doc.Entities.Add(LwPline);
        using (var writer = new DxfWriter(input, doc, true))
        {
            writer.OnNotification += NotificationHelper.LogConsoleNotification;
            writer.Write();
        }
    }

//Program 2 public static void DrawPolylineTest(string input) { CadDocument doc = new CadDocument(); List vector2d = new List(){ new Vertex2D(){Location = new XYZ(0,0,0)}, new Vertex2D(){Location = new XYZ(1,0,0)}, new Vertex2D(){Location = new XYZ(2,1,0)}, new Vertex2D(){Location = new XYZ(3,1,0)}, new Vertex2D(){Location = new XYZ(4,4,0)} };

        var Pline = new Polyline2D();
        Pline.Vertices.AddRange(vector2d);
        Pline.Flags = PolylineFlags.ClosedPolylineOrClosedPolygonMeshInM;
        Pline.Vertices.ElementAt(3).Bulge = 1;

        doc.Entities.Add(Pline);
        using (var writer = new DxfWriter(input, doc, true))
        {
            writer.OnNotification += NotificationHelper.LogConsoleNotification;
            writer.Write();
        }

    }

DomCR / ACadSharp

LwPolyline is always closed, Polyline2d.Vertices cannot set Bulge, and Dxf opening in CAD Error #174