How to implement Auditing system in C# in webservice?

I created a webservice for my application. In that webservice i'm accessing SQL server for Datas. Now the feature, i've to implement is, i have to check some table at some time and based the value i need to notify customer. I can achieve this by implementing new controller(i already have controller for views). Now my question is, will this break any standard structure? Is there pattern i should follow for including this type of feature to application? Stackoverflow must have multiple service for their rewarding system and notification system. They also did like this? if there is any better approach please let me know.