Material reference

Hi reviteers,

There are 7 types ofExternalFileReferenceTypes.

I am using this code to retrieve references in a revit project:

ICollection<ElementId> externalReferences = transData.GetAllExternalFileReferenceIds();

I can retrieve:

ExternalFileReferenceType.AssemblyCodeTable

ExternalFileReferenceType.CADLink

ExternalFileReferenceType.RevitLink

ExternalFileReferenceType.KeynoteTable

but there is also a

ExternalFileReferenceType.Material

But the code above never gets materials ??

What is this setting for ? Is it supposed to retrieve the rendermaterials ? And if so, why doesn't the code above retrieve them ??

Is the a way to get a list of missing materials and fix the links ?