Web API is a framework that helps you to create and develop HTTP based RESTFUL services to be consumed by a 3rd party system. This feature can be useful to reach a broad range of clients including different platforms such as mobile applications, software, or web-based application.
You can develop your own Web API in Kentico Projects.
The instruction on how to do that already describe in Kentico documentation here:
K8.1 - https://docs.xperience.io/k81/developing-websites/using-asp-net-web-api-with-kentico
K8.2 - https://docs.xperience.io/k82/developing-websites/using-asp-net-web-api-with-kentico
K9 - https://docs.xperience.io/k9/developing-websites/using-asp-net-web-api-with-kentico
K10 - https://docs.xperience.io/k10/developing-websites/using-asp-net-web-api-with-kentico
K11 - https://docs.xperience.io/k11/developing-websites/using-asp-net-web-api-with-kentico
K12 - https://docs.xperience.io/k12sp/integrating-3rd-party-systems/using-asp-net-web-api-with-kentico
K13 - https://docs.xperience.io/integrating-3rd-party-systems/using-asp-net-web-api-with-xperience
Some of you have an issue when following the step by step described in the documentation above even they follow one by one on the guide. For my case, After following the steps, I'm receiving an error like the image below.
The issue is because the Web API projects using latest version from what CMS Kentico already installed.
To solve this issue, you need to open the NuGet package for your solution and update Kentico Library to use the latest version OR you might need to downgrade the library package used for your Web API to the lower version(recommended).
The recommended solution is because to avoid any issue for other Kentico modules that already working well with the old version Library.