C# converting tree of lists to GH_DataTree<Line>

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Permalink Reply by David Rutten on July 11, 2016 at 11:30am

Hi Abdulmalik,

I'm a bit confused. When you say a "tree of : system.collections.generic.list1[rhino.geometry.line]", what does that mean?

• GH_Structure<List<Line>>
• DataTree<List<Line>>
• List<Line>
• ...?

Permalink Reply by Abdulmalik Abdulmawla on July 11, 2016 at 3:16pm

Thanks David for your quick reply..

well i have a c# library that generate a DataTree<List<Line>> and it comes out as shown in the panel

I have tried to access it as System.Object, but i am missing something in the parsing process probably !

I am just trying to extract this long tree to lists into lines

Permalink Reply by Abdulmalik Abdulmawla on July 11, 2016 at 3:45pm

i was wondering how can i differ between

GH_Structure<List<Line>> and DataTree<List<Line>>

i am having second thoughts on the tree type, i am afraid it might be GH_Structure !!

Permalink Reply by Abdulmalik Abdulmawla on July 11, 2016 at 5:28pm

ok , i solved it with a very strange line ..

A = x;

but x is an Item Access of  System.object 

Permalink Reply by David Rutten on July 12, 2016 at 5:44am

Grasshopper knows what a Rhino.Geometry.Line is, but it does not understand what it is supposed to do with a List<Line>. It'll store it in a data tree, but beyond that it cannot handle the concept.

The Script components however do have a very coarse understanding of collection classes, when you output a type which implements IEnumerable<T> and which is not already a 'known' type* it will try to unpack that collection and put the entire collection into a data tree ranch. This is probably why A = x; worked for you because it allows the script component to inspect and unpack the lists.

DataTree and GH_Structure are annoyingly similar yet non-overlapping classes. GH_Structure is used by Grasshopper itself to store data, DataTree is a version that was made specifically for the use inside script components. This part of the SDK is a mess but there's nothing we can do about it at this point.

If you want to convert a DataTree<List<Line>> into a Data<Line>, you have to decide whether you want each list to end up being a unique branch, or whether you're happy to just merge all the lines in all the lists that already share a branch. The code will look a little bit different in each case.

* Known types include Polyline which is an IEnumerable<Point3d>, string which is an IEnumerable<char> and so on, we assume these types need to remain intact.

Permalink Reply by Abdulmalik Abdulmawla on July 13, 2016 at 3:04am

Thanks David,

This is still very strange to automatically unpack data without any reference stating that this is possible :) , it is good to know , but it was a surprise to try such a silly line and get results !!

Anyway if i will convert DataTree<List<Line>> into a Data<Line>, i would always keep each list as a branch, but this would not be much of an issue now since i was having trouble converting "system.collections.generic.list1[rhino.geometry.line]" into  List<Line> in the first place

Many thanks,

Malik