Functional F# that slowly appears in C#

For some reason, we often do not use this functionality. Maybe we haven’t got used to it yet. And sometimes we use it, having no idea that this is the functionality from F#. Before reviewing it, let’s quickly run through the most interesting features that appeared in different versions of the language. Note that each time a new version of the language comes out with a new version of Visual Studio. For someone, this may be obvious, but even for developers who have worked with C# for several years, this may turn out to be a piece of news (not everyone takes notice of it).