Pro WPF in C# 2010: Windows Presentation Foundation in .NET 4

18.1. Understanding Custom Elements in WPF

Although you can code a custom element in any WPF project, you'll usually want to place custom elements in a dedicated class library (DLL) assembly. That way, you can share your work with multiple WPF applications.

To make sure you have the right assembly references and namespace imports, you should choose the Custom Control Library (WPF) project type when you create your application in Visual Studio. Inside your class library, you can create as many or as few controls as you like.

As with all class library development, it's often a good practice to place both your class library and the application that ...