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c#ifcbimxbim

Get system with elements from a model

How do I get the elements in a HVAC system? I can access the list of the systems in a model with the following code:

var systems = model.Instances.OfType<IfcSystem>();

This returns a list of all the systems in the model. How to access the elements in a system?

Solution

  • So this is a matter of understanding the IFC data model by looking at the standards - in particular the Group Assignment data model: https://standards.buildingsmart.org/IFC/RELEASE/IFC4_1/FINAL/HTML/link/group-assignment.htm

    In IFC, an IfcSystem subclasses IfcGroup. To get the members of a Group you need to access the IfcRelAssignsToGroup relationship provided via IsGroupedBy, from where you can get the RelatedObjects collection containing the actual elements.

    So in xbim you'd end up with something like:

    var hvacSystem = model.Instances.OfType<IfcSystem>().First(s => s.GlobalId="<Your Hvac Identifier>");

var hvacElements = hvacSystem.IsGroupedBy?.RelatedObjects.OfType<IIfcProduct>();