“else if()” versus multiple “if()”s in C#

Question

How do these practically differ?

// Approach one
if (x == 1)
    DoSomething();
else if (x == 2)
    DoSomethingElse();

// Approach two
if (x == 1)
    DoSo         


        

Answer 1

When you use else statement, only one of the branches will be run (i.e. the first, which meets the if condition). All other if conditions won't even be estimated:

// approach one
int x = 1;
if (x == 1)
    DoSomething(); //only this will be run, even if `DoSomething` changes `x` to 2
else if (x == 2)
    DoSomethingElse();

While when you don't use it each of them may be run (depending on each of the conditions), i.e. each of them is estimated one by one:

// approach two
int x = 1;
if (x == 1)
    DoSomething();//this is run, as `x` == 1
if (x == 2)
    DoSomethingElse();//if `DoSomething` changes `x` to 2, this is run as well

So, IL may differ.