Best way to format if statement with multiple conditions

I prefer Option A

bool a, b, c;

if( a && b && c )
{
   //This is neat & readable
}

If you do have particularly long variables/method conditions you can just line break them

if( VeryLongConditionMethod(a) &&
    VeryLongConditionMethod(b) &&
    VeryLongConditionMethod(c))
{
   //This is still readable
}

If they're even more complicated, then I'd consider doing the condition methods separately outside the if statement

bool aa = FirstVeryLongConditionMethod(a) && SecondVeryLongConditionMethod(a);
bool bb = FirstVeryLongConditionMethod(b) && SecondVeryLongConditionMethod(b);
bool cc = FirstVeryLongConditionMethod(c) && SecondVeryLongConditionMethod(c);

if( aa && bb && cc)
{
   //This is again neat & readable
   //although you probably need to sanity check your method names ;)
}

IMHO The only reason for option 'B' would be if you have separate else functions to run for each condition.

e.g.

if( a )
{
    if( b )
    {
    }
    else
    {
        //Do Something Else B
    }
}
else
{
   //Do Something Else A
}

Other answers explain why the first option is normally the best. But if you have multiple conditions, consider creating a separate function (or property) doing the condition checks in option 1. This makes the code much easier to read, at least when you use good method names.

if(MyChecksAreOk()) { Code to execute }

...

private bool MyChecksAreOk()
{ 
    return ConditionOne && ConditionTwo && ConditionThree;
}

It the conditions only rely on local scope variables, you could make the new function static and pass in everything you need. If there is a mix, pass in the local stuff.

The first example is more "easy to read".

Actually, in my opinion you should only use the second one whenever you have to add some "else logic", but for a simple Conditional, use the first flavor. If you are worried about the long of the condition you always can use the next syntax:

if(ConditionOneThatIsTooLongAndProbablyWillUseAlmostOneLine
                 && ConditionTwoThatIsLongAsWell
                 && ConditionThreeThatAlsoIsLong) { 
     //Code to execute 
}

Good Luck!

The question was asked and has, so far, been answered as though the decision should be made purely on "syntactic" grounds.

I would say that the right answer of how you lay-out a number of conditions within an if, ought to depend on "semantics" too. So conditions should be broken up and grouped according to what things go together "conceptually".

If two tests are really two sides of the same coin eg. if (x>0) && (x<=100) then put them together on the same line. If another condition is conceptually far more distant eg. user.hasPermission(Admin()) then put it on it's own line

Eg.

if user.hasPermission(Admin()) {
   if (x >= 0) && (x < 100) {
      // do something
   }
}

The second one is a classic example of the Arrow Anti-pattern So I'd avoid it...

If your conditions are too long extract them into methods/properties.

The first one is easier, because, if you read it left to right you get: "If something AND somethingelse AND somethingelse THEN" , which is an easy to understand sentence. The second example reads "If something THEN if somethingelse THEN if something else THEN", which is clumsy.

Also, consider if you wanted to use some ORs in your clause - how would you do that in the second style?

In Perl you could do this:

{
  ( VeryLongCondition_1 ) or last;
  ( VeryLongCondition_2 ) or last;
  ( VeryLongCondition_3 ) or last;
  ( VeryLongCondition_4 ) or last;
  ( VeryLongCondition_5 ) or last;
  ( VeryLongCondition_6 ) or last;

  # Guarded code goes here
}

If any of the conditions fail it will just continue on, after the block. If you are defining any variables that you want to keep around after the block, you will need to define them before the block.

I've been facing this dilemma for a long time and I still can't find a proper solution. In my opinion only good way is to first try to get rid of conditions before so you're not suddenly comparing 5 of them.

If there's no alternative then like others have suggested - break it down into separete ones and shorten the names or group them and e.g. if all must be true then use something like "if no false in array of x then run".

If all fails @Eoin Campbell gave pretty good ideas.