In this article, we will implement a CRUD Operation in Web API using one-many relationship tables. Web API: Web API is a framework for building HTTP services that can be accessed from any client like browser, mobile devices, and desktop apps. In Simple terminology API(Application Programming Interface) means an interface module that contains a programing function that can be requested via HTTP calls either to fetch or update data for their respective clients. Some of the key characteristics of API: Support HTTP verbs like 'GET', 'POST', 'PUT', 'DELETE', etc. Support default responses like 'XML' and 'JSON'. Also can define custom responses. Supports self-hosting or individual hosting, so that all different kinds of apps can consume it. Authentication and Authorization are easy to implement. SQL Script For One-Many Relationship Tables: For this demo, we are going to create sample tables like 'Customer' & 'CustomerAddresses&