CreateNewSweptBlend.cs

public Result Execute(ExternalCommandData commandData, ref string message, ElementSet elements)
        {
            Autodesk.Revit.Creation.Application app = commandData.Application.Application.Create;
            Document doc = commandData.Application.ActiveUIDocument.Document;
            using (Transaction tran = new Transaction(doc, "Test"))
            {
                tran.Start();
                //ElementId id = doc.GetElement(new ElementId(1)).Id;
                CreateNewSweptBlend(commandData.Application.ActiveUIDocument.Document);
                tran.Commit();

                return Result.Succeeded;
            }
        }

        public void CreateNewSweptBlend( Document doc )
        {
            var app = doc.Application;

            Autodesk.Revit.Creation.Application creapp 
                = app.Create;
 
            CurveArrArray curvess0 
                = creapp.NewCurveArrArray();
 
            CurveArray curves0 = new CurveArray();
 
            XYZ p00 = creapp.NewXYZ( 0, 7.5, 0 );
            XYZ p01 = creapp.NewXYZ( 0, 15, 0 );
 
            // changing Z to 1 in the following line fails:
 
            XYZ p02 = creapp.NewXYZ( -1, 10, 0 );
 
            curves0.Append( Line.CreateBound( p00, p01 ) );
            curves0.Append(  Line.CreateBound( p01, p02 ) );
            curves0.Append(  Line.CreateBound( p02, p00 ) );
            curvess0.Append( curves0 );
 
            CurveArrArray curvess1 = creapp.NewCurveArrArray();
            CurveArray curves1 = new CurveArray();
 
            XYZ p10 = creapp.NewXYZ( 7.5, 0, 0 );
            XYZ p11 = creapp.NewXYZ( 15, 0, 0 );
 
            // changing the Z value in the following line fails:
 
            XYZ p12 = creapp.NewXYZ( 10, -1, 0 );
 
            curves1.Append(  Line.CreateBound( p10, p11 ) );
            curves1.Append(  Line.CreateBound( p11, p12 ) );
            curves1.Append(  Line.CreateBound( p12, p10 ) );
            curvess1.Append( curves1 );
 
            SweepProfile sweepProfile0 
                = creapp.NewCurveLoopsProfile( curvess0 );
 
            SweepProfile sweepProfile1 
                = creapp.NewCurveLoopsProfile( curvess1 );
 
            XYZ pnt10 = new XYZ( 5, 0, 0 );
            XYZ pnt11 = new XYZ( 0, 20, 0 );
            Curve curve =  Line.CreateBound( pnt10, pnt11 );
 
            XYZ normal = XYZ.BasisZ;

            Plane plane = Plane.CreateByNormalAndOrigin(normal, new XYZ(0, 0, 0));
            SketchPlane splane = SketchPlane.Create(doc,plane);
 
            try
            {
                SweptBlend sweptBlend = doc.FamilyCreate.NewSweptBlend( 
                    true, curve, splane, sweepProfile0, sweepProfile1 );
            }
            catch( Exception ex )
            {
                MessageBox.Show(ex.ToString());
            }
        }