This chapter will help you understand how to extend the behavior of Dynamics 365 CE using custom code. We will learn about the extendibility architecture of Dynamics 365 CE and the layers where we can extend Dynamics 365 CE. We will discuss how we can write client-side code for entity forms and fields. We will also discuss options for retrieving entity data using Web API code. Later, we will discuss details about plugin development, such as writing plugin assembly, registering plugin assembly, and debugging plugin code to implement our custom logic using server-side code. Debugging plugins will help you troubleshoot any issues with plugin development. 

The main topics that we are going to discuss in this chapter are as follows: 

• Extendibility architecture
• Implementing client-side logic
• Implementing server-side logic
• Implementing custom logic using plugins
• Debugging plugin code