Do not call Destroy to free a TSOAPAttachment object. Instead, use the Free method, which checks for a nil reference before calling Destroy. 

On server applications, there is typically no need to explicitly free a TSOAPAttachment instance (for example, one created as a return value or output parameter). By default, when a TSOAPAttachment descendant is created in a method that was called remotely using an invokable interface, it is added to a data context (the value of the DataContext property). As long as the remotable object belongs to the data context, the data context handles freeing the object. Similarly, TSOAPAttachment instances that are passed in as a parameter belong to the data context. 

On client applications, TSOAPAttachment instances created and passed to an invokable interface or returned as a parameter or result of an invokable interface must be freed by the calling application. 

DataContext 

Free