Gets the ids of all elements which refer to external resources. 
   Namespace:   Autodesk.Revit.DB  
  Assembly:   RevitAPI  (in RevitAPI.dll) Version: 2015.0.0.0 (2015.0.0.0) 
  Since:  2015 
Syntax
| C# | 
|---|
|  | 
| Visual Basic | 
|---|
|  | 
| Visual C++ | 
|---|
|  | 
Parameters
- document
-  Type:  Autodesk.Revit.DB Document  
 The Revit Document containing the external resource references.
Return Value
The ids of all elements which refer to external resources.Remarks
 This function will not return the ids of nested Revit links; it only returns top-level references. 
 Exceptions
| Exception | Condition | 
|---|---|
| Autodesk.Revit.Exceptions ArgumentNullException | A non-optional argument was NULL |