Constexpr like keyword in C#

in C++, I can have a function (e.g. Fibonacci) like below:

constexpr int Fibonacci(int n) {
//cout << "Executed Fib" << endl;
switch (n) {
case 0: return 0;
case 1: return 1;
default:
return Fibonacci(n - 1) + Fibonacci(n - 2);
}

}

and I can check in the main to ensure the function is correct by doing something like:

int main()
{
static_assert(Fibonacci(5) == 7, "Bad Program");
///...
}

That means I do not have to wait till run time to evaluate if the Fibonacci function will work. It is like a simple test at a compile-time. I am asking if I can do thing kind of thing in C#.

Thanks. I updated the question.