Duplicate check on email addresses during new contact creation or editing a existing contact in C4C

Hi All,

We want to achieve duplicate check on email addresses of new contact creation or on editing an existing contact in C4C. Requirement is to not allow contact saving if the email address already exists in the system. can you please help and guide which business object must be used here if anyone has achieved this requirement earlier. Also, a few lines of code would be helpful to start as I am very new to C4C.