When to use custom control?

• When you have a rapid and fixed content in your UI, use UserControl.
• When you want to separate some basic functionality of your main view to some smaller pieces with reusability, use UserControl.
• When you want to use your control in different projects and each project may want to change the look, use CustomControl.
• When you want to implement some additional functionality for a control, create a CustomControl derived from the base control.
• When you want to apply themes to your controls, use CustomControl.
• When you want to add toolbox support for your control, so that your user will be able to do drag and drop to the designer, use CustomControl.