Console.WriteLine was around before interpolated strings was a feature in C# since ,NET version 1.1 if I recall correctly. Interpolated strings was introduced somewhere in the C# 4.0 to 6.0 versions (I'm going off of memory). Using the trace service's Trace method, you can absolutely bypass this syntax and just use interpolated strings instead, as most people are doing.
However, because you asked, here's a breakdown of the TraceWriter.Trace/Console.WriteLine/String.Format syntax which appears to all use String.Format underneath the hood. Links to String.Format documentation which will go through the various possibilities: https://docs.microsoft.com/en-us/dotnet/api/system.string.format?view=net-5.0
Take a statement like this:
var cloudCondition = "Sunny";
var message = String.Format("The skies today will be {0}.", cloudCondition);
The first parameter is a string template, informing Format about the general structure of what to output. The {0} syntax within the template informs String.Format to use the parameter to this method in the 0 position (0 based arrays). The first parameter following the string template is the 0 position param (cloudCondition). When format sees the {0}, it will replace it with the value of cloudCondition.
You can reuse the params within the template. There's a great example under the "Insert a string" in the link above, so I'll spare the words here.
Honestly, use the interpolated strings instead of trying to learn this syntax unless you need special formatting capabilities only offered by the String.Format method.
Links:
Console.WriteLine: https://docs.microsoft.com/en-us/dotnet/api/system.console.writeline?view=net-5.0
String.Format: https://docs.microsoft.com/en-us/dotnet/api/system.string.format?view=net-5.0
I hope this helps!
