When should I use WPF instead of Windows Forms?

WPF is clearly more suitable for applications with rich media, but some people have said that Windows Forms is the best choice for business applications with traditional
user interfaces. I think this belief is based on beta versions of WPF in which many standard controls didn't exist (such as TreeView, ListView, and OpenFileDialog) and a
visual designer didn't exist, making traditional Windows application development in WPF harder than in Windows Forms.

Although Windows Forms still has useful controls that WPF lacks (such as DataGridView and PropertyGrid) and at the time of writing has a larger set of third-party controls in the marketplace, WPF has compelling features even for traditional user interfaces

So unless running on Windows 98 is important (which is still supported by Windows Forms 2.0 but not by WPF), I would recommend WPF over Windows Forms for a broad
range of applications—especially after Visual Studio "Orcas" is released. But Windows Forms isn't going away anytime soon; there just won't be major enhancements
made to it after version 2.0 was released in 2005. Microsoft is clearly investing in WPF—not Windows Forms—as the future presentation platform.