C# If statment execution order

[NvrBst]

In C# if(exp1 && exp2 && exp3)

Does it evalutate left to right (exp1 -> exp2 -> exp3)? or right to
left (exp3 -> exp2 -> exp1)? Or would it execute all of them even if
exp1 turned out to be false?

Thanks

 

[Michael C]

In C# if(exp1 && exp2 && exp3)

Does it evalutate left to right (exp1 -> exp2 -> exp3)? or right to
left (exp3 -> exp2 -> exp1)? Or would it execute all of them even if
exp1 turned out to be false?

Left to right.

 

[Jon Skeet [C# MVP]]

In C# if(exp1 && exp2 && exp3)

Does it evalutate left to right (exp1 -> exp2 -> exp3)? or right to
left (exp3 -> exp2 -> exp1)? Or would it execute all of them even if
exp1 turned out to be false?

It will evaluate exp1, then only if that's true will it evalute exp2,
then only if that's true will it evaluate exp3.

In other words, it does the intuitively "right" thing.

Jon

 

[Maate]

AND moreover it stops evaluating if an expression is false opposed to
the & operator, e.g.:

String nul = null;
String test = "test";
if (nul != null && test.Length > nul.Length)
Response.Write("test");

will NOT result in an exception, while this will:

String nul = null;
String test = "test";
if (nul != null & test.Length > nul.Length)
Response.Write("test");

because the latter will try to evaluate the expression test.Length >
nul.Length, where nul = null.

Morten

 

[Michael S]

In C# if(exp1 && exp2 && exp3)

Does it evalutate left to right (exp1 -> exp2 -> exp3)? or right to
left (exp3 -> exp2 -> exp1)? Or would it execute all of them even if
exp1 turned out to be false?

Thanks

When I was forced into a VB.NET project I was laughing myself to tears when
I learned about the AndAlso and OrElse keywords.

But to be fair, guess they had add those keywords do make it easier to port
VB6 code without breaking logic.

- Michael S

 

[Michael C]

String nul = null;
String test = "test";
if (nul != null & test.Length > nul.Length)
Response.Write("test");

I really hope you don't call variables nul in production code.

Michael

 

[Michael C]

When I was forced into a VB.NET project I was laughing myself to tears
when I learned about the AndAlso and OrElse keywords.

But to be fair, guess they had add those keywords do make it easier to
port VB6 code without breaking logic.

They really can't win, they change things people complain, if they leave
them the same (and add new keyword for the changes) then people complain.

 

[=?ISO-8859-1?Q?Arne_Vajh=F8j?=]

I really hope you don't call variables nul in production code.

There are great potential for obfuscating code.

if(nul == null || Null == null || nulL == null || Null == nul || nulL ==
Null)



Arne

 

[=?ISO-8859-1?Q?Arne_Vajh=F8j?=]

When I was forced into a VB.NET project I was laughing myself to tears when
I learned about the AndAlso and OrElse keywords.

The short circuit is very practical.

The situation where the second test can not be executed if
the first test does not succeed is very common.

if(x != null && x.something())

But from a puristic point of view, then the alternative
tend to enforce more clear code.

if(a && b.changesomeglobalstate())

Arne

 

[Jon Skeet [C# MVP]]

The short circuit is very practical.

The situation where the second test can not be executed if
the first test does not succeed is very common.

if(x != null && x.something())

But from a puristic point of view, then the alternative
tend to enforce more clear code.

if(a && b.changesomeglobalstate())

I'd rather have practical than pure any day

However, you can always use the non-short-circuiting "&" operator
instead:

if (a & b.ChangeSomeGlobalState())
....

 

[Michael C]

There are great potential for obfuscating code.

if(nul == null || Null == null || nulL == null || Null == nul || nulL ==
Null)

After writing such code you will be truly irreplacable.

Michael

 

[=?ISO-8859-1?Q?G=F6ran_Andersson?=]

After writing such code you will be truly irreplacable.

Michael

const True = false;
const fa1se = !True;

also helps.