What are the three Register directive attributes used to add custom controls to a Web form?

 

TagPrefix: The TagPrefix defines a unique namespace for an user control. If multiple user controls are present on the page having same name, then they can be differentiated with them by using this directive. It determines the group that the user control belongs to.

Namespace: It is nothing but the project name and namespace within the custom control assembly that contains the controls to register. The .NET applications use the project name as an implicit namespace for controls present in the application.

Assembly: This defines the name of the created assembly (.dll) that contains the custom controls. The control assembly is referenced by the Web application and it maintains a copy in the web applications 'Bin' directory.