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SDK XAML Browser
The SDK XAML Browser from Microsoft lets you select a layout container or control in the navigation panel, then shows you the XAML and a rendering of the control in isolation in the main panel.
Type Explorer
XamlT—short for XAML Type Explorer—provides a unique interface to examining class diagrams specifically for WPF classes.
Gradient Editor
This Gradient Editor lets you define a color gradient graphically with an arbitrary number of bands and returns a XAML code fragment for you to paste into your application.
Read more: simple-talk