使用revit api画垂直于风管的风管示例

/// <summary>
/// 选择风管与风管外一点，画与风管垂直的风管。
/// </summary>
[transaction(transactionmode.manual)]
[regeneration(regenerationoption.manual)]
public class cmd : iexternalcommand
{
    public result execute(externalcommanddata cmddata, ref string msg, elementset elements)
    {
        uidocument uidoc = cmddata.application.activeuidocument;
        uiapplication uiapp = cmddata.application;
        document doc = uidoc.document;
        selection selection = uidoc.selection;

        transaction ts = new transaction(doc, "//www.jb51.net");
        ts.start();
        //得到一种风管类型
        ducttype ducttype = null;
        filteredelementcollector collector = new filteredelementcollector(doc);
        collector.ofclass(typeof(ducttype));
        foreach (element el in collector.toelements())
        {
            ducttype = el as ducttype;
            break;
        }
        //
        reference refduct = selection.pickobject(objecttype.element, "选择一根风管：");
        duct duct = doc.getelement(refduct) as duct;
        xyz xyz = selection.pickpoint();//选择一点
        locationcurve lcurve = duct.location as locationcurve;
        intersectionresult interresult = lcurve.curve.project(xyz);//点在直线上的投影
        if (interresult != null)
        {
            doc.create.newduct(xyz, interresult.xyzpoint, ducttype);
        }
        ts.commit();
        return result.succeeded;
    }
}