Creating railing inside a loop: Element Table in Revit's database

[MiguelGT17]

Greetings to everyone,

I'm collecting the boundary lines for every room then Im looking to generate railings base on those lines but I'm facing the following error:

                foreach (Room room in rooms)
                {
                      ...getting boundary lines and group then to theBottomLinesLoop

                        if (theBottomLinesLoop.Any()) {
                        	
                        	//foreach line check if lines continue
                        	//CurveLoop cvL = CurveLoop.Create(new List<Curve>{theBottomLinesLoop[0]});
                        	//Railing rail = Railing.Create(doc,cvL,railType.Id,level.Id);
                        	
                        	foreach (Line line in theBottomLinesLoop) {
                        		CurveLoop cvL = CurveLoop.Create(new List<Curve>{line});
                        		Railing rail = Railing.Create(doc,cvL,railType.Id,level.Id);
                        	}
                        }

If I comment the Railing.Create(doc,...) line, no errors are thrown However I cant place the railings lol,

I'm confused about this matter, any possible explanation to this issue?

Best regards,

Miguel G.

[mhannonQ65N2 · Accepted solution]

I suspect your rooms variable is a FilteredElementCollector or a lazily evaluated IEnumerable<Room> that is fed from a FilteredElementCollector. This means that with each iteration of your loop over rooms, the FilteredElementsCollector processes more elements until it finds the next matching element or is done. When you make changes to the document while the FilteredElementCollector is iterating, it causes this error. To fix it, just call ToElements() on your FilteredElementCollector or call ToArray() at the end of your LINQ method chain for rooms so it finished iterating before you make any changes to the document.

[MiguelGT17]

What such a great community we have here! thank you @mhannonQ65N2 for your prompt reply! that was the issue, initially my collector was declared as:

//before
IEnumerable<Element> rooms = new FilteredElementCollector(doc).OfClass(typeof(SpatialElement)).Where<Element>(e => e is Room);


//after
List<Element> rooms = new FilteredElementCollector(doc).OfClass(typeof(SpatialElement)).Where<Element>(e => e is Room).ToList();