Awesome
AvaloniaRider 
Install
Stable Release
Either search for Avalonia on the Plugins settings page or visit the Plugin Marketplace.
Development Release
To install a development release (automatically published for every push into a development branch), first add the custom plugin repository into your IDE (see the documentation on how to do that).
Custom plugin repository address:
https://plugins.jetbrains.com/plugins/dev/14839
Then, install the plugin as usual via the IDE plugin settings screen.
How to Use
Previewer
Make sure your Avalonia project is built, open an XAML file, and you'll see an XAML preview in Rider.
It's possible to interact with the previewer using the mouse, and zoom with Ctrl+Scroll Wheel.
There's a separate button to debug the previewer process for the current file, but it's hidden by default. To enable that feature, go to the Avalonia settings page in Rider and enable the Developer mode checkbox.
File templates
Right-click a directory or an Avalonia-enabled project and choose among the available file templates:
- Avalonia User Control
- Avalonia Templated control
- Avalonia Window
- Avalonia Resource Dictionary
- Avalonia Styles
Live templates
Type in an editor to use Live templates:
directProperty,styledProperty,attachedAvaloniaProperty.