Which is faster if-else or Switch case ?

[D KARTHICK]

Which is faster if-else or Switch case ?

 

[xwb]

Depends on what you are doing - sometimes, it can be solved by simple arithmetic, which is faster than both. What exactly are you trying to do?

For example, if a number is 5, make it 2, if it is 2, make it 5. It could be coded as

' if statement - assuming it will only ever be 2 or 5
if x = 5 then
    x = 2
else
    x = 5
end if

' arithmetic - assuming it will only ever be 2 or 5
x = 7 - x

 

[jbenson001]

Technically, a Switch / Case statement is faster because in an IF Statment, each IF / ElseIF is evaluated. In a Switch/Case, once the condition is met, the Switch/Case is exited.
Personally, I find Switch/Case to look cleaner and more readable as well. If it is just a small check as in xwb's example, then I would just use a standard IF or to shorten it I would use an InLine IF. The syntax differs between VB and C#

 

[xwb]

It really depends on the internal implementation of the switch statement.

If the cases are sequential, very often, the implementation is the equivalent of a computed goto. For example

    switch (x)
    {
    case 8: ...; break;
    case 5: ...; break;
    case 7: ...; break;
    case 6: ...; break;
    }

The compiler would arrange them as 5, 6, 7,8, subtract 5 from x and use a computed goto.

If the cases are not sequential, they could be sorted into a lookup table followed by a computed goto. Alternatively, it could be implemented as an if-elseif-else statement. If it is the latter then there is no difference between the switch and the if-elseif-else other than possibly elegance of the code.

 

[jbenson001]

An IF statement will always evaluate each condition. A switch will fall through once the condition is met. True, depending on the conditions, they could be equal in performance, but the switch will win out in most cases.