Properties.Cancel is obsolete in SharePoint 2013
The properties.Cancel is now obsolete. Instead use properties.Status. This has several options.
SPEventReceiverStatus..CancelNoError
SPEventReceiverStatus.CancelWithError
SPEventReceiverStatus..CancelWithRedirectUrl
SPEventReceiverStatus.Continue
This is an improvement from the old way which was a boolean so you just had 2 options. Now you have 4. 