[CONNECT C++] ReadAndLoadDgnAttachments() takes much time if reference file cannot be found

Hi,

I have a model which references to many other files, but these files are all missing. (see the picture below)

It surpreised me that ReadAndLoadDgnAttachments() takes almost 15 seconds.

bool loadCaches=true;
bool loadUndisplayed=true;
bool loadRasterRefs=true;

DgnAttachmentLoadOptions refLoadOption (loadCaches, loadUndisplayed, loadRasterRefs);
model.ReadAndLoadDgnAttachments (refLoadOption);

I also tried to create a model which referenced to many unfound files, but the performance issue for the ReadAndLoadDgnAttachments() cannot be reproduced.

So my question is

(1) Which factors will affect the performance of ReadAndLoadDgnAttachments()?

(2) Is there any methods to judge the referenced file is missing or not before calling ReadAndLoadDgnAttachments()?

Thanks,

Richard