WPF: CustomControls vs UserControls

Question

In WPF, what is the differences between CustomControls and UserControls? When should I use each?

Answer 1

UserControl (Composition):

• Composes multiple existing controls into a reusable "group"
• Consists of a XAML and a code behind file
• Cannot be styled/templated
• Derives from UserControl

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CustomControl (Extending an existing control)

• Extends an existing control with additional features
• Consists of a code file and a default style in Themes/Generic.xaml
• Can be styled/templated
• The best approach to build a control library

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Source: The differences between CustomControls and UserControls