Usually where I see C# slow down is not because of the language, but because of over engineered "enterprisey" solutions that Java has a bad rep for e.g. having things like a FactoryProviderFactory type idioms.
A lot of the projects I work on, for instance, heavily utilize dependency injection for no gain. There's only one implementation, theres no test mocks. Its just overengineered and obsfuscated for no reason.
Coming from a predominantly C++ background, we eschew virtual wherever possible, favoring compile time polymorphism to runtime whenever possible, because we're cognizant of the overhead of the indirect dispact and likely loss of optimized opportunities to inline trivial calls.
For sure, one can write C# or Java that can keep up, or even outperform C++ in some circumstances, but youre not going to do it with "enterprise" patterns hiding behind interfaces and factories and dependency injection.
COM/UWP is not only for GUIs, it is the full area of modern Windows APIs.
Then there are ORM like the ill fated POET.
Yeah just like not everyone is writing code that "eschew virtual wherever possible, favoring compile time polymorphism to runtime whenever possible", specially on large corporations with mixed language teams.
Beyond C++ conference talks, I am yet to see stuff like SFINAE and tag dispatching in the C++ code I occasionally deal with. Grated those are libraries that get called from Java/.NET projects.
I have written a fair amount of C++ template metaprogramming and policy based libraries. One library I wrote, in particular, was a templated generic matching engine primarily used in the self-clearing of trades. Through template policies, it could be configured to do one-to-one, on-to-many, many-to-many matching based upon template args, for example. I also did a bit of SFINAE in writing a home-grown ORM lib. I haven't really written any libs using tag dispatching, but I've certainly used my fair share (looking at you, Boost MultiIndex).
You don't usually see these sorts of types wrapped for Java or .Net, and if they are, you usually have some sort of proxy in between to hide the templates.
A lot of the projects I work on, for instance, heavily utilize dependency injection for no gain. There's only one implementation, theres no test mocks. Its just overengineered and obsfuscated for no reason.
Coming from a predominantly C++ background, we eschew virtual wherever possible, favoring compile time polymorphism to runtime whenever possible, because we're cognizant of the overhead of the indirect dispact and likely loss of optimized opportunities to inline trivial calls.
For sure, one can write C# or Java that can keep up, or even outperform C++ in some circumstances, but youre not going to do it with "enterprise" patterns hiding behind interfaces and factories and dependency injection.