Logical AND (&&) in an If Statement

[Charles Law]

This is a very basic question, but I can' turn up a statement on the
subject:

In C#, if I have

If (x == 1 && y == 2)
{
....
}

Suppose x is not equal to 1, does the logical test for y == 2 still get
executed?

TIA

Charles

[Leo Seccia]

Hello Charles,

With && if the frist part is false the second part is not evaluated AKA
"short circuit evaluation".
With a single & the second part is evaluated unconditionally.

http://msdn.microsoft.com/en-us/libr...dk(VS.71).aspx

Regards,
Leo
"Charles Law" <bl***@nowhere.comwrote in message
news:%2****************@TK2MSFTNGP02.phx.gbl...

This is a very basic question, but I can' turn up a statement on the
subject:

In C#, if I have

If (x == 1 && y == 2)
{
...
}

Suppose x is not equal to 1, does the logical test for y == 2 still get
executed?

TIA

Charles

[Marc Gravell]

No; the && and || operators are short-circuited:

* if the first operand in a && is false, then false is returned
without looking at the second operand
* if the first operand in a || is true, then true is returned without
looking at the second operand

Marc

[zacks]

On May 7, 7:55*am, "Charles Law" <[e-mail]:

This is a very basic question, but I can' turn up a statement on the
subject:

In C#, if I have

If (x == 1 && y == 2)
{
...

}

Suppose x is not equal to 1, does the logical test for y == 2 still get
executed?

TIA

Charles

If you have any VB.NET experiance, the && and || operators are
equivalent to the VB.NET AndAlso and OrElse operators.

[Charles Law]

Thanks Leo and Marc for the replies.

What was concerning me was that in the following:

const int expectedlength = 10;

byte[] myarray;

// assign to myarray
...

If (myarray.GetLength(0) == expectedlength && myarray[expectedlength -
1] == 0x1)
{
...
}

If the array was not the expected length then the subsequent test could
cause an IndexOutOfRange exception.

Charles
"Marc Gravell" <ma**********@gmail.comwrote in message
news:13**********************************@m36g2000 hse.googlegroups.com...

No; the && and || operators are short-circuited:

* if the first operand in a && is false, then false is returned
without looking at the second operand
* if the first operand in a || is true, then true is returned without
looking at the second operand

Marc

[Jon Skeet [C# MVP]]

On May 7, 2:26 pm, "Charles Law" <[e-mail]:

Thanks Leo and Marc for the replies.

What was concerning me was that in the following:

const int expectedlength = 10;

byte[] myarray;

// assign to myarray
...

If (myarray.GetLength(0) == expectedlength && myarray[expectedlength -
1] == 0x1)
{
...
}

If the array was not the expected length then the subsequent test could
cause an IndexOutOfRange exception.

No, that should be fine. I'd use the Length property instead of
GetLength(0) though, just for the sake of readability.

Jon

[Charles Law]

Hi Jon

Thanks for the confirmation; and noted about the Length suggestion.

Cheers

Charles
"Jon Skeet [C# MVP]" <sk***@pobox.comwrote in message
news:27**********************************@l64g2000 hse.googlegroups.com...

On May 7, 2:26 pm, "Charles Law" <[e-mail]:

>Thanks Leo and Marc for the replies.

What was concerning me was that in the following:

const int expectedlength = 10;

byte[] myarray;

// assign to myarray
...

If (myarray.GetLength(0) == expectedlength &&
myarray[expectedlength -
1] == 0x1)
{
...
}

If the array was not the expected length then the subsequent test could
cause an IndexOutOfRange exception.

No, that should be fine. I'd use the Length property instead of
GetLength(0) though, just for the sake of readability.

Jon

[Charles Law]

Hi Zacks

If you have any VB.NET experiance, the && and || operators are
equivalent to the VB.NET AndAlso and OrElse operators.

I have, as I generally use VB.NET, so that makes sense to me.

Thanks.

Charles
<za***@construction-imaging.comwrote in message
news:2a**********************************@a23g2000 hsc.googlegroups.com...
On May 7, 7:55 am, "Charles Law" <[e-mail]:

This is a very basic question, but I can' turn up a statement on the
subject:

In C#, if I have

If (x == 1 && y == 2)
{
...

}

Suppose x is not equal to 1, does the logical test for y == 2 still get
executed?

TIA

Charles

If you have any VB.NET experiance, the && and || operators are
equivalent to the VB.NET AndAlso and OrElse operators.