Checks if the fabrication item files are already in use and should not be unloaded. 
   Namespace:   Autodesk.Revit.DB  
  Assembly:   RevitAPI  (in RevitAPI.dll) Version: 22.0.0.0 (22.1.0.0) 
  Since:  2019 
Syntax
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Parameters
- itemFiles
-  Type:  System.Collections.Generic IList   FabricationItemFile  
 The fabrication item files to unload.
Return Value
Returns true if the fabrication item files can be unloaded, false otherwise.Exceptions
| Exception | Condition | 
|---|---|
| Autodesk.Revit.Exceptions ArgumentNullException | A non-optional argument was null |