In this post i want to mention and differentiate between 2 types of changes on any WCF service.
when you are developing a wcf servive,the changes might occur,and before any change you have to test and examine does this change will affect the service clients ?
The changes you have done on a WCF Service,it will affect the client anyway,but the type of the change it might break the client which yield to the client will not work OR it might yield to the client can continues working in a healthy way.
NON Breaking Changes:
Implicit or Explict security checks,change on the logic of the function,add extra binding configuration...etc
Change Method paramaters , Add new paramaeters,change return types,delete methods.
Any Change which will break the client,you have to inform the client owner with the change you have done,to keep the client working.
Hope this helps.