Discards all changes made to the model during the sub-transaction. 
   Namespace:   Autodesk.Revit.DB  
  Assembly:   RevitAPI  (in RevitAPI.dll) Version: 2015.0.0.0 (2015.0.0.0) 
  Since:  2011 
Syntax
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Return Value
If finished successfully, this method returns TransactionStatus.RolledBack.Remarks
The parent transaction (or a parent sub-transaction, if any) can still be committed, but the changes rolled back by this method will not be part of the committed transaction.
RollBack can be called only when all inner sub-transaction, if any, are finished, i.e. they were either committed or rolled back. If there is still a sub-transaction open, an attempt to roll this outer sub-transaction back will cause an exception.
Exceptions
| Exception | Condition | 
|---|---|
| Autodesk.Revit.Exceptions InvalidOperationException | A sub-transaction can only be active inside an open Transaction. -or- The sub-transaction's current status is not TransactionStatus.Started, therefore it may not be committed or rolled back. |