Rider has Unity support built in, and the very first time you open a Unity solution it will automatically configure Unity to use Rider as the default editor for C# scripts and shader files. Once done, double-clicking a C# script or shader asset will open the solution in Rider.
The source code is shown very nicely in the editor, and on the left hand side there's the project view where you can see all of the files and folders in your project. This is very nice because it's not showing you the solution files but it's showing you a view very similar to the project view in Unity itself.
You can see all of your assets and expand to any of these folders and see our what files are available in there.