Enhancements for .NET Core 2 examples

[SheepReaper]

additional explanations in the examples, simplified some code, tidied up, and replaced .ReadLine() with .ReadKey() (Since we want to exit with ANY key).

thanks for all the awesome @304NotModified and @snakefoot

[codecov]

Codecov Report

Merging #243 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #243   +/-   ##
=======================================
  Coverage   71.42%   71.42%           
=======================================
  Files           8        8           
  Lines         448      448           
  Branches      112      112           
=======================================
  Hits          320      320           
  Misses         85       85           
  Partials       43       43

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[304NotModified]

Thanks!