2021-07-17C＃/CAD二次开发创建圆（5）

Circle c1 = new Circle();
c1.Center = new Point3d(50, 50, 0);
c1.Radius = 50;

Circle c2 = new Circle(new Point3d(100, 100, 0), new Vector3d(0, 0, 1), 50);

创建圆的类Circle有如上两种方法：
先通过Circle创建一个对象，然后再给他的圆心、半径赋值
或者直接创建时赋值。

绘制圆和圆弧一样，封装到AddEnityTool.ca代码如下

        /// <summary>
        /// 绘制圆
        /// </summary>
        /// <param name="db">图形数据库</param>
        /// <param name="center">圆心</param>
        /// <param name="radius">半径</param>
        /// <returns></returns>
        public static ObjectId AddCircleModelSpace(Database db, Point3d center, double radius)
        {
    
            return AddEnityTool.AddEnityToModelSpace(db, new Circle(center, new Vector3d(0, 0, 1), radius));
        }
        /// <summary>
        /// 两点绘制圆
        /// </summary>
        /// <param name="db">图形数据库</param>
        /// <param name="point1">第一个点</param>
        /// <param name="point2">第二个点</param>
        /// <returns>ObjectId</returns>
        public static ObjectId AddCircleModelSpace(Database db, Point3d point1, Point3d point2) 
        {
    
            //获取中心点
            Point3d center = BaseTool.GetCenterPointBetweenTwoPoint(point1, point2);
            //获取半径
            double radius = BaseTool.GetDistanceBetweenTwoPoint(point1, center);
            return AddEnityTool.AddCircleModelSpace(db, center, radius);
        }
        /// <summary>
        /// 三点绘制圆
        /// </summary>
        /// <param name="db">图形数据库</param>
        /// <param name="point1">第一个点</param>
        /// <param name="point2">第二个点</param>
        /// <param name="point3">第三个点</param>
        /// <returns>ObjectId</returns>
        public static ObjectId AddCircleModelSpace(Database db, Point3d point1, Point3d point2, Point3d point3)
        {
    
            //先判断三点是否在同一直线上
            if (BaseTool.IsOnOneLine(point1, point2, point3))
            {
    
                return ObjectId.Null;
            }
            //声明几何类的CircularArc3d对象
            CircularArc3d cArc = new CircularArc3d(point1, point2, point3);
            return AddEnityTool.AddCircleModelSpace(db, cArc.Center, cArc.Radius);
        }
    }
}