Sets a custom duplicate type names handler. If this value is not set, the default handler is used. By default, Revit displays a modal dialog with options to either copy new types only, or cancel the operation. 
   Namespace:   Autodesk.Revit.DB  
  Assembly:   RevitAPI  (in RevitAPI.dll) Version: 2015.0.0.0 (2015.0.0.0) 
  Since:  2014 
Syntax
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Parameters
- handler
-  Type:  Autodesk.Revit.DB IDuplicateTypeNamesHandler  
 The duplicate type names handler.
Exceptions
| Exception | Condition | 
|---|---|
| Autodesk.Revit.Exceptions ArgumentNullException | A non-optional argument was NULL |