API could be in any form - be it a dll lib, wcf or rest so I am pasting a resource for each. 1. Restful API with WCF - https://msdn.microsoft.com/en-us/library

API could be in any form - be it a dll lib, wcf or rest so I am pasting a resource for each. 1. Restful API with WCF - https://msdn.microsoft.com/en-us/library/dd203052.aspx https://msdn.microsoft.com/en-us/library/dd203052.aspx 2. Restful API using WebAPI - https://github.com/Microsoft/api-guidelines/blob/master/Guidelines.md https://github.com/Microsoft/api-guidelines/blob/master/Guid... 3. API via dll - https://www.amazon.com/Framework-Design-Guidelines-Conventions-Libraries/dp/0321545613/ref=sr_1_1?s=books&ie=UTF8&qid=1470852593&sr=1-1&keywords=framework+design+guidelines https://www.amazon.com/Framework-Design-Guidelines-Conventio...