Exploring magic commands

Throughout this book, we’ve seen a number of magic commands, such as #r, #!connect, and #import. In this section, we’ll discuss a few other magic commands and talk about how they are implemented at a high level. Put simply, magic commands are special methods triggered by unusual syntax, referred to as directives.

When a kernel in .NET Interactive encounters a registered directive, it follows the following approximate sequence:

1. The directive is marked as ignored and not treated as code by the language kernel. In other words, the C# kernel won’t attempt to compile a #r magic command.
2. Any relevant parameters are identified and extracted from the command. For example, the #r "nuget:Microsoft.ML" command extracts the NuGet string as a parameter and errors if it is not specified.
3. .NET Interactive creates an instance of a relevant KernelCommand object and sets properties as needed. We’ll talk more about this...