After working in c# for a year, the only conclusion I can come to is
You can always start to learn it.
But you will discover that it is not very rewarding to program in C, because
it take ages before you have something that actually works. And it is even
harder to keep up with the new technology to extend that C program. Very
time consuming.
And I do not talk about the ever strugle with the header files, search
paths, link errors, and a zillion of errors in your output screen because
you forgot a ';' and all the errors try to point you in the wrong direction.
But in my opinion, you should at least have tried C/C++. And you can indeed
program parts of the program that needs the higest performance. And you
should also try assembly language. This helps a lot to understand why some
functions are faster than other, and you can create even faster code in C if
you know how the processor works. Especialy in 2D loops, and why the 'true'
part of the if-then-els should contain the most used code than the else
part.