In theory, if the feature provided by the library is very important (apparently it is important enough for C# implementors to build it in the language), you can

In theory, if the feature provided by the library is very important (apparently it is important enough for C# implementors to build it in the language), you can expect that the library will eventually becomes standard or quasi-standard. For any language, its programmer is expected to learn not only the language features but also standard libraries, so eventually the difference of "knowing" part will be leveled out. In practice, there are two factors that work in opposite directions, and which factor you're looking at changes pros and cons of language feature vs. library discussion. * Time difference - for language features you have to wait until implementors implement them. For libraries you can start immediately. That gives you time advantage, sometimes for as much as years. * Pressure difference - to make it standard language features there are lots of pressures to make it right, and effort is taken accordingly. Similar amount of effort is needed to make a library feature into standard position. But for those who wrote that library feature in the first place, usually their need is fulfilled easily, so there may not be enough incentives for them to push the feature into standard. I feel the time advantage the 'library' approach gives me is crucial, so I prefer flexible languages (specifically I use Scheme). But in this side I do see the effect of the latter---there are tons of libraries, each of which is "good enough" for a specific circumstance but a bit short to be truly general, reliable solution.