Having been away from WPF for a long time, it was a pleasant surprise for me to find this when building a small tool a few days ago:
XAML Hot Reload is a feature that causes changes in XAML to immediately be reflected in an application running in debug mode. It applies to WPF and UWP applications, and is currently in preview for Xamarin Forms apps.
Update 7th November 2019: thanks to the Twitter user who pointed out that this feature has been around for three years under the name “XAML Edit and Continue” for WPF and UWP apps. It recently got rebranded and extended to Xamarin Forms.
Basically, if I go and change the XAML for the above window (making it even uglier than it already is) while the application is still running, the changes are applied instantly as soon as I save the file:
This kind of live-reload has existed in the web development space for a while thanks to technologies such as Browsersync. However, it is nice to see it finally arrive in the much-neglected realm of desktop application development, for those still stuck in it.