/// <summary>
        /// 绘制风扇
        /// </summary>
        /// <param name="dxf"></param>
        /// <param name="startPoint">风扇起点，如果为横置，由左向右；如果为竖置，由下到上</param>
        /// <param name="endPoint">风扇终点，如果为横置，由左向右；如果为竖置，由下到上</param>
        /// <param name="pointerLocation">箭头位置，默认=0为无，=1代表箭头在中间，=2代表箭头在底部</param>
        public static void Draw(DxfDocument dxf, Vector3f startPoint, Vector3f endPoint,int pointerLocation=0)
        {
            Layer layer = new Layer("line");
            Line line = new Line(startPoint, endPoint);
            line.Layer = layer;
            dxf.AddEntity(line);

            //如果为横置
            if (startPoint.Y == endPoint.Y)
            {
                float segment = (endPoint.X - startPoint.X) / 4;
                Slash.Draw(dxf, new Location(startPoint.X + segment, startPoint.Y, startPoint.Z));
                Slash.Draw(dxf, new Location(startPoint.X + 2 * segment, startPoint.Y, startPoint.Z));
                Slash.Draw(dxf, new Location(startPoint.X + 3 * segment, startPoint.Y, startPoint.Z));
            }
            //如果为竖置
            else if (startPoint.X == endPoint.X)
            {
                float segment = (endPoint.Y - startPoint.Y) / 5;
                Slash.Draw(dxf, new Location(startPoint.X, startPoint.Y + segment, startPoint.Z));
                Slash.Draw(dxf, new Location(startPoint.X, startPoint.Y + 2 * segment, startPoint.Z));
                Slash.Draw(dxf, new Location(startPoint.X, startPoint.Y + 3 * segment, startPoint.Z));
                Slash.Draw(dxf, new Location(startPoint.X, startPoint.Y + 4 * segment, startPoint.Z));
                if (pointerLocation == 1)
                {
                    LinePointer.Draw(dxf,new Location(startPoint.X,(startPoint.Y+endPoint.Y)/2,startPoint.Z));
                }
                else if(pointerLocation==2)
                {
                    LinePointer.Draw(dxf, new Location(startPoint.X, startPoint.Y, startPoint.Z));
                }
            }
        }

 /// <summary>
 /// Initializes a new instance of the <c>PolyfaceMeshFace</c> class.
 /// </summary>
 /// <remarks>
 /// By default the face is made up of three vertexes.
 /// </remarks>
 public PolyfaceMeshFace()
     : base(DxfObjectCode.Vertex)
 {
     this.flags = VertexTypeFlags.PolyfaceMeshVertex;
     this.vertexIndexes = new int[3];
     this.layer = Layer.Default;
     this.color = AciColor.ByLayer;
     this.lineType = LineType.ByLayer;
 }

 /// <summary>
 /// Intitializes a new instance of the <c>Attribute</c> class.
 /// </summary>
 /// <param name="definition"><see cref="AttributeDefinition">Attribute definition</see>.</param>
 /// <param name="value">Attribute value.</param>
 public Attribute(AttributeDefinition definition, object value)
     : base(DxfObjectCode.Attribute)
 {
     this.definition = definition;
     this.value = value;
     this.color = definition.Color;
     this.layer = definition.Layer;
     this.lineType = definition.LineType;
 }

 /// <summary>
 /// Initializes a new instance of the <c><Polyline3dVertex/c> class.
 /// </summary>
 public Polyline3dVertex()
     : base(DxfObjectCode.Vertex)
 {
     this.flags = VertexTypeFlags.Polyline3dVertex;
     this.location = Vector3d.Zero;
     this.layer = Layer.Default;
     this.color = AciColor.ByLayer;
     this.lineType = LineType.ByLayer;
 }

 /// <summary>
 /// Initializes a new instance of the <c>PolylineVertex</c> class.
 /// </summary>
 /// <param name="location">Polyface mesh vertex <see cref="Vector3d">location</see>.</param>
 public PolyfaceMeshVertex(Vector3d location)
     : base(DxfObjectCode.Vertex)
 {
     this.flags = VertexTypeFlags.PolyfaceMeshVertex | VertexTypeFlags.Polygon3dMesh;
     this.location = location;
     this.layer = Layer.Default;
     this.color = AciColor.ByLayer;
     this.lineType = LineType.ByLayer;
 }

 /// <summary>
 /// Initializes a new instance of the <c>PolyfaceMesh</c> class.
 /// </summary>
 public PolyfaceMesh()
     : base(DxfObjectCode.Polyline)
 {
     this.flags = PolylineTypeFlags.PolyfaceMesh;
     this.faces = new List<PolyfaceMeshFace>();
     this.layer = Layer.Default;
     this.color = AciColor.ByLayer;
     this.lineType = LineType.ByLayer;
     this.endSequence = new EndSequence();
 }

 /// <summary>
 /// Initializes a new instance of the <c>Polyline3d</c> class.
 /// </summary>
 /// <param name="vertexes">3d polyline <see cref="Polyline3dVertex">vertex</see> list.</param>
 public Polyline3d(List<Polyline3dVertex> vertexes)
     : base(DxfObjectCode.Polyline)
 {
     this.flags = PolylineTypeFlags.Polyline3D;
     this.vertexes = vertexes;
     this.layer = Layer.Default;
     this.color = AciColor.ByLayer;
     this.lineType = LineType.ByLayer;
     this.endSequence = new EndSequence();
 }

        public static void Draw(DxfDocument dxf, Location location)
        {
            Vector3f v1 = new Vector3f(location.X - 2.0f, location.Y - 4.0f, location.Z);
            Vector3f v2 = new Vector3f(location.X + 2.0f, location.Y + 4.0f, location.Z);
            Layer layer = new Layer("line");

            Line line12 = new Line(v1, v2);
            line12.Layer = layer;
            dxf.AddEntity(line12);
        }

 /// <summary>
 /// Initializes a new instance of the <c>Point</c> class.
 /// </summary>
 public Point()
     : base(DxfObjectCode.Point)
 {
     this.location = Vector3d.Zero;
     this.thickness = 0.0f;
     this.layer = Layer.Default;
     this.color = AciColor.ByLayer;
     this.lineType = LineType.ByLayer;
     this.normal = Vector3d.UnitZ;
 }

        /// <summary>
        /// 风向绘制
        /// </summary>
        /// <param name="dxf"></param>
        /// <param name="location"></param>
        /// <param name="isRight"></param>
        public static void Draw(DxfDocument dxf, Location location, bool isRight)
        {
            float factor = 0.5f;
            Vector3f v1 = new Vector3f();
            Vector3f v2 = new Vector3f();
            Vector3f v3 = new Vector3f();
            Vector3f v4 = new Vector3f();
            Vector3f v5 = new Vector3f();
            Vector3f v6 = new Vector3f();
            Vector3f v7 = new Vector3f();
            if (isRight)
            {
                v1 = new Vector3f(10*factor + location.X, location.Y, location.Z);
                v2 = new Vector3f(location.X, location.Y + 10 * factor, location.Z);
                v3 = new Vector3f(location.X + 10 * factor, location.Y + 10 * factor, location.Z);
                v4 = new Vector3f(location.X + 20 * factor, location.Y + 15 * factor, location.Z);
                v5 = new Vector3f(location.X, location.Y + 20 * factor, location.Z);
                v6 = new Vector3f(location.X + 10 * factor, location.Y + 20 * factor, location.Z);
                v7 = new Vector3f(location.X + 10 * factor, location.Y + 30 * factor, location.Z);
            }
            else
            {
                v1 = new Vector3f(10 * factor + location.X, location.Y, location.Z);
                v2 = new Vector3f(location.X + 20 * factor, location.Y + 10 * factor, location.Z);
                v3 = new Vector3f(location.X + 10 * factor, location.Y + 10 * factor, location.Z);
                v4 = new Vector3f(location.X, location.Y + 15 * factor, location.Z);
                v5 = new Vector3f(location.X + 20 * factor, location.Y + 20 * factor, location.Z);
                v6 = new Vector3f(location.X + 10 * factor, location.Y + 20 * factor, location.Z);
                v7 = new Vector3f(location.X + 10 * factor, location.Y + 30 * factor, location.Z);
            }
            Layer layer = new Layer("line");
            Line line23 = new Line(v2, v3);
            line23.Layer = layer;
            dxf.AddEntity(line23);

            Line line56 = new Line(v5, v6);
            line56.Layer = layer;
            dxf.AddEntity(line56);

            Line line14 = new Line(v1, v4);
            line14.Layer = layer;
            dxf.AddEntity(line14);

            Line line74 = new Line(v7, v4);
            line74.Layer = layer;
            dxf.AddEntity(line74);

            Line line25 = new Line(v2, v5);
            line25.Layer = layer;
            dxf.AddEntity(line25);

            Line line71 = new Line(v7, v1);
            line71.Layer = layer;
            dxf.AddEntity(line71);
        }

 protected virtual Layer OnLayerChangeEvent(Layer oldLayer, Layer newLayer)
 {
     LayerChangeEventHandler ae = this.LayerChange;
     if (ae != null)
     {
         TableObjectChangeEventArgs<Layer> eventArgs = new TableObjectChangeEventArgs<Layer>(oldLayer, newLayer);
         ae(this, eventArgs);
         return eventArgs.NewValue;
     }
     return newLayer;
 }

 /// <summary>
 /// Initializes a new instance of the <c>Circle</c> class.
 /// </summary>
 public Circle()
     : base(DxfObjectCode.Circle)
 {
     this.center = Vector3d.Zero;
     this.radius = 1.0;
     this.thickness = 0.0f;
     this.layer = Layer.Default;
     this.color = AciColor.ByLayer;
     this.lineType = LineType.ByLayer;
     this.normal = Vector3d.UnitZ;
 }

 /// <summary>
 /// Initializes a new instance of the <c>Line</c> class.
 /// </summary>
 public Line()
     : base(DxfObjectCode.Line)
 {
     this.startPoint = Vector3d.Zero;
     this.endPoint = Vector3d.Zero;
     this.thickness = 0.0f;
     this.layer = Layer.Default;
     this.color = AciColor.ByLayer;
     this.lineType = LineType.ByLayer;
     this.normal = Vector3d.UnitZ;
 }

 /// <summary>
 /// Initializes a new instance of the <c>PolylineVertex</c> class.
 /// </summary>
 /// <param name="location">Polyline <see cref="Vector2d">vertex</see> coordinates.</param>
 public PolylineVertex(Vector2d location)
     : base(DxfObjectCode.Vertex)
 {
     this.flags = VertexTypeFlags.PolylineVertex;
     this.location = location;
     this.layer = Layer.Default;
     this.color = AciColor.ByLayer;
     this.lineType = LineType.ByLayer;
     this.bulge = 0.0f;
     this.beginThickness = 0.0f;
     this.endThickness = 0.0f;
 }

 /// <summary>
 /// Initializes a new instance of the <c>Arc</c> class.
 /// </summary>
 /// <param name="center">Arc <see cref="netDxf.Vector3d">center</see> in object coordinates.</param>
 /// <param name="radius">Arc radius.</param>
 /// <param name="startAngle">Arc start angle in degrees.</param>
 /// <param name="endAngle">Arc end angle in degrees.</param>
 /// <remarks>The center Z coordinate represents the elevation of the arc along the normal.</remarks>
 public Arc(Vector3d center, double radius, double startAngle, double endAngle)
     : base(DxfObjectCode.Arc)
 {
     this.center = center;
     this.radius = radius;
     this.startAngle = startAngle;
     this.endAngle = endAngle;
     this.thickness = 0.0f;
     this.layer = Layer.Default;
     this.color = AciColor.ByLayer;
     this.lineType = LineType.ByLayer;
     this.normal = Vector3d.UnitZ;
 }

 /// <summary>
 /// Initializes a new instance of the <c>Solid</c> class.
 /// </summary>
 /// <param name="firstVertex">Solid <see cref="Vector3d">first vertex</see>.</param>
 /// <param name="secondVertex">Solid <see cref="Vector3d">second vertex</see>.</param>
 /// <param name="thirdVertex">Solid <see cref="Vector3d">third vertex</see>.</param>
 /// <param name="fourthVertex">Solid <see cref="Vector3d">fourth vertex</see>.</param>
 public Solid(Vector3d firstVertex, Vector3d secondVertex, Vector3d thirdVertex, Vector3d fourthVertex)
     : base(DxfObjectCode.Solid)
 {
     this.firstVertex = firstVertex;
     this.secondVertex = secondVertex;
     this.thirdVertex = thirdVertex;
     this.fourthVertex = fourthVertex;
     this.thickness = 0.0f;
     this.normal = Vector3d.UnitZ;
     this.layer = Layer.Default;
     this.color = AciColor.ByLayer;
     this.lineType = LineType.ByLayer;
 }

 /// <summary>
 /// Initializes a new instance of the <c>NurbsCurve</c> class.
 /// </summary>
 public NurbsCurve()
 {
     this.controlPoints = new List<NurbsVertex>();
     this.normal = Vector3d.UnitZ;
     this.layer = Layer.Default;
     this.color = AciColor.ByLayer;
     this.lineType = LineType.ByLayer;
     this.order = 0;
     this.curvePoints = 30;
     this.elevation = 0.0;
     this.thickness = 0.0f;
     this.normal = Vector3d.UnitZ;
 }

 /// <summary>
 /// Initializes a new instance of the <c>Polyline</c> class.
 /// </summary>
 /// <param name="vertexes">Polyline <see cref="LightWeightPolylineVertex">vertex</see> list in object coordinates.</param>
 /// <param name="isClosed">Sets if the polyline is closed</param>
 public LightWeightPolyline(List<LightWeightPolylineVertex> vertexes, bool isClosed)
     : base(DxfObjectCode.LightWeightPolyline)
 {
     this.vertexes = vertexes;
     this.isClosed = isClosed;
     this.layer = Layer.Default;
     this.color = AciColor.ByLayer;
     this.lineType = LineType.ByLayer;
     this.normal = Vector3d.UnitZ;
     this.elevation = 0.0;
     this.thickness = 0.0f;
     this.flags = isClosed ? PolylineTypeFlags.ClosedPolylineOrClosedPolygonMeshInM : PolylineTypeFlags.OpenPolyline;
 }

        /// <summary>
        /// Initializes a new instance of the <c>Block</c> class.
        /// </summary>
        /// <param name="name">Block name.</param>
        public Block(string name)
            : base(DxfObjectCode.Block)
        {
            if (string.IsNullOrEmpty(name))
                throw (new ArgumentNullException("name"));

            this.name = name;
            this.basePoint = Vector3d.Zero;
            this.layer = Layer.Default;
            this.attributes = new Dictionary<string, AttributeDefinition>();
            this.entities = new List<IEntityObject>();
            this.record=new BlockRecord(name);
            this.end = new BlockEnd(this.layer);
        }

 /// <summary>
 /// Initializes a new instance of the <c>Text</c> class.
 /// </summary>
 public Text()
     : base(DxfObjectCode.Text)
 {
     this.value = string.Empty;
     this.basePoint = Vector3d.Zero;
     this.alignment = TextAlignment.BaselineLeft;
     this.layer = Layer.Default;
     this.color = AciColor.ByLayer;
     this.lineType = LineType.ByLayer;
     this.normal = Vector3d.UnitZ;
     this.style = TextStyle.Default;
     this.rotation = 0.0f;
     this.height = 0.0f;
     this.widthFactor = 1.0f;
     this.obliqueAngle = 0.0f;
 }