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在 xbim 示例https://docs.xbim.net/examples/basic-model-operations.html的基本操作中，它显示了如何检索特定 IfcElement 的单值属性。基于此，我试图获取材料数据。

我写了以下内容：

var id = "3NBPkknun6EuV9fpeE6rFh";

var theWall = model.Instances.FirstOrDefault<IIfcElement>(d => d.GlobalId == id);

var materials = theWall.HasAssociations
                        .Where(r => r.RelatingMaterial is IIfcMaterialProfileSet)
                        .SelectMany(r=> ((IIfcMaterialProfileSet)r.RelatingMaterial).MaterialProfiles)
                        .OfType<IIfcMaterialProfile>();

它给了我这个错误：

“IIfcRelAssociates”不包含“RelatingMaterial”的定义，并且找不到接受“IIfcRelAssociates”类型的第一个参数的可访问扩展方法“RelatingMaterial”（您是否缺少 using 指令或程序集引用？）

我知道我必须使用 IfcRelAssociatesMaterial，但我不知道如何使用。如何检索材料信息？

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1 回答 1

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IIfcObjectDefinition's HasAssociations returns a set of IIfcRelAssociates but you want just the derived type IIfcRelAssociatesMaterial which has the RelatingMaterial property. See https://standards.buildingsmart.org/IFC/RELEASE/IFC4/ADD2/HTML/schema/ifcproductextension/lexical/ifcrelassociatesmaterial.htm

So, it's just a matter of adding .OfType<IIfcRelAssociatesMaterial> to constrain the query to Material associations. i.e.

var materials = theWall.HasAssociations.OfType<IIfcRelAssociatesMaterial>() 
// rest of the query
于 2020-06-16T18:08:21.970 回答