title: How / Why can visual studio give suggestions / hints while making a Regex string?
body: <p>First, a little context as to what I mean. I've recently started learning some basics of Regex and wanted to try it in .NET. In Visual Studio 2019, while working in C#, I can make a <code>Regex</code> object. I was astonished and amazed when I saw that Visual Studio is actually giving me hints as to the syntax of the &quot;Regex language&quot; (so to speak), which it will also color appropriately. Here is a picture of what I mean:</p>
  <p><a href="https://i.stack.imgur.com/GA3YE.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/GA3YE.png" alt="regex hints" /></a></p>
  <p>With that in mind, my questions is: Does this happen just because it is built-in to Visual Studio, to show this when editing this particular argument of Regex? Or, if not, how and where exactly is it stated how it should give hints for the string? Is it some sort of advanced <code>&lt;Summary&gt;</code> like tagging?</p>
  <p>Can I, for example, implement something like that for my classes so that custom hints are given out when making strings in my classes' methods?</p>