Diffrences Between Custom Control and User Control:
Custom Control
- You can create a Custom control when it is going to be used across different applications.
- Custom controls don't a visual interface.
- Custom controls however can be added to your tool box and used in different applications without re-compiling.
- It's a .dll
User Control
- If the control you are going to create is only for a particular website then User Control is the best option.
- User controls have a visual interface.
- User control will not appear in tool box and it will not have design support and loaded at runtime.
- It's a .ascx