Tewr's comment is right on the spot as this is a scenario suited for EWS (Exchange Web Services).
If you're using MVC 5 to develop this application, it may be the most helpful to use EWS Managed API to access the Exchange server as it allows you to all of it in C#.
Managed API - http://msdn.microsoft.com/en-us/library/office/jj220499(v=exchg.80).aspx
Working with contacts - http://msdn.microsoft.com/en-us/library/office/ee693004(v=exchg.80).aspx