[Transaction(TransactionMode.Automatic)]
[Regeneration(RegenerationOption.Manual)]
[Journaling(JournalingMode.NoCommandData)]
//根据选中的两个风管，创建弯头
public class CreateElbow : IExternalCommand
{
    public Result Execute(ExternalCommandData commandData, ref string messages, ElementSet elements)
    {
        UIApplication uiApp = commandData.Application;
        Document doc = uiApp.ActiveUIDocument.Document;
        Selection sel = uiApp.ActiveUIDocument.Selection;

//选取两个风管
        Duct duct1 = sel.PickObject(ObjectType.Element, "请选择第1个风管").Element as Duct;
        Duct duct2 = sel.PickObject(ObjectType.Element, "请选择第2个风管").Element as Duct;

//先得到两条直线和两个连接器
        IList<XYZ> list1 = new List<XYZ>();
        IList<Connector> conn1 = new List<Connector>();
        ConnectorSetIterator csi1 = duct1.ConnectorManager.Connectors.ForwardIterator();
        while (csi1.MoveNext())
        {
            Connector conn = csi1.Current as Connector;
            list1.Add(conn.Origin);
            conn1.Add(conn);
        }

IList<XYZ> list2 = new List<XYZ>();
        IList<Connector> conn2 = new List<Connector>();
        ConnectorSetIterator csi2 = duct2.ConnectorManager.Connectors.ForwardIterator();
        while (csi2.MoveNext())
        {
            Connector conn = csi2.Current as Connector;
            list2.Add(conn.Origin);
            conn2.Add(conn);
        }

//再得到交点
        Curve curve1 = Line.get_Bound(list1.ElementAt(0), list1.ElementAt(1)) as Curve;
        Curve curve2 = Line.get_Bound(list2.ElementAt(0), list2.ElementAt(1)) as Curve;
        curve1.MakeUnbound();
        curve2.MakeUnbound();

IntersectionResultArray intersectionR = new IntersectionResultArray();//交点集合
        SetComparisonResult comparisonR;//Comparison比较
        comparisonR = curve1.Intersect(curve2, out intersectionR);//直线交点

XYZ intersectionResult = null;//交点坐标
        if (SetComparisonResult.Disjoint != comparisonR)//Disjoint不交
        {
            if (!intersectionR.IsEmpty)
            {
                intersectionResult = intersectionR.get_Item(0).XYZPoint;
            }
        }

/*
        //判断直线上哪个点离交点近
        XYZ near1 = list1.ElementAt(0);
        if(intersectionResult.DistanceTo(list1.ElementAt(0))>intersectionResult.DistanceTo(list1.ElementAt(1)))
        {
            near1 = list1.ElementAt(1);
        }

XYZ near2 = list2.ElementAt(0);
        if (intersectionResult.DistanceTo(list2.ElementAt(0)) > intersectionResult.DistanceTo(list2.ElementAt(1)))
        {
            near2 = list2.ElementAt(1);
        }

//找到对应的连接器
        Connector connector1 = null;
        foreach (Connector iConnector in conn1)
        {
            if (iConnector.Origin.IsAlmostEqualTo(near1))
            {
                connector1 = iConnector;
            }
        }

Connector connector2 = null;
        foreach (Connector iConnector in conn2)
        {
            if (iConnector.Origin.IsAlmostEqualTo(near2))
            {
                connector2 = iConnector;
            }
        }
        */
        //改进,直接设置连接器。
        Connector connector1 = conn1.ElementAt(0);
        if (intersectionResult.DistanceTo(list1.ElementAt(0)) > intersectionResult.DistanceTo(list1.ElementAt(1)))
        {
            connector1 = conn1.ElementAt(1);
        }

Connector connector2 = conn2.ElementAt(0);
        if (intersectionResult.DistanceTo(list2.ElementAt(0)) > intersectionResult.DistanceTo(list2.ElementAt(1)))
        {
            connector2 = conn2.ElementAt(1);
        }

//创建弯头
        if (null != connector1 && null != connector2)
        {
            doc.Create.NewElbowFitting(connector1, connector2);
        }

return Result.Succeeded;
    }
}