Is there any significant difference between using if/else and switch-case in C#?

Question

What is the benefit/downside to using a switch statement vs. an if/else in C#. I can\'t imagine there being that big of a difference, other than m

Answer 1

Not just C#, but all C-based languages, I think: because a switch is limited to constants, it's possible to generate very efficient code using a "jump table". The C case is really a good old FORTRAN computed GOTO, but the C# case is still tests against a constant.

It is not the case that the optimizer will be able to make the same code. Consider, eg,

if(a == 3){ //...
} else if (a == 5 || a == 7){ //...
} else {//...
}

Because those are compound booleans, the generated code has to compute a value, and shortcircuit. Now consider the equivalent

switch(a){
   case 3: // ...
    break;
   case 5:
   case 7: //...
    break;
   default: //...
}

This can be compiled into

BTABL: *
B3:   addr of 3 code
B5:
B7:   addr of 5,7 code
      load 0,1 ino reg X based on value
      jump indirect through BTABL+x

because you are implicitly telling the compiler that it doesn't need to compute the OR and equality tests.