Nested inline if statement

Question

In VB .Net it is possible to use inline If statements, like this

if a Then ret = "A" Else ret = "Not A"

I know it is also possible to nest these statements. I know this might not be good practice as readability drops down...

If a Then If b Then ret = "A & B" Else ret = "A & Not B" Else ret = "Not A"

which will be evaluated like this :

If a Then
    If b Then
        ret = "A & B"
    Else
        ret = "A & Not B"
    End If
Else
    ret = "Not A"
End If

Now if I remove the last Else statement, I get this :

If a Then If b Then ret = "A & B" Else ret = "A & Not B"

which is :

If a Then
    If b Then
        ret = "A & B"
    Else
        ret = "A & Not B"
    End If
End If

So I guess the compiler finds the Else and matches it to the last openend If in the line, which makes sense. My question is : Is it possible to change the evaluation order ? By that I mean is it possible that the Else is matched with the first if ?

So it would look like this :

If a Then
    If b Then
        ret = "A & B"
    End If
Else
    ret = "Not A"
End If

But inlined (something like this, parenthesis added to understand what I mean) :

If a Then ( If b Then ret = "A & B" ) Else ret = "Not A"

I tried with parenthesis or adding a End If but it provokes syntax errors, and I couldn't find documentation for this.

I'm not stuck anywhere and I know this might not be a good prorgamming practice, but I just wanted to know (out of curiosity) if it was possible.

I know also I could switch the statements (i.e. test b before a), but let's say I can't (a is a List and must be tested for Nothing before b which would be the Count for example).

If you are confusing the compiler, imagine yourself trying to make sense of that 6 months down the road — Ňɏssa Pøngjǣrdenlarp
– Ňɏssa Pøngjǣrdenlarp, Commented Nov 10, 2016 at 15:04

the_lotus · Accepted Answer · 2016-11-10 14:57:52Z

6

You could do it like this

ret = If(a, If(b, "A & B", "A & Not B"), "Not A")

Personally, I never understood the need to put everything in one line.

answered Nov 10, 2016 at 14:57

the_lotus

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7 Comments

Martin Verjans Over a year ago

Problem with this is that both statements get evaluated (From here).

Ňɏssa Pøngjǣrdenlarp Over a year ago

That link says the opposite @MartinVerjans. Short circuiting means only the part that applies is evaluated. the inner If will only execute when a is true otherwise it "jumps" to the false part

Ňɏssa Pøngjǣrdenlarp Over a year ago

The If operator is different than the If statement though @MartinVerjans

the_lotus Over a year ago

@MartinVerjans IIF behave differently than IF.

Martin Verjans Over a year ago

Is there any imports to do or reference to add ? Using VS 2012 Express and .Net 3.5, the compiler doesn't recognize it...

|

baudsp · Accepted Answer · 2016-11-10 15:58:54Z

2

You may find that this is what you need:

If a And B Then

   ret = "A & B"

Else

   ret = "Not A"

End If

Or as a single line:

If A And B Then Ret = "A & B" Else RET = "Not A"

edited Nov 10, 2016 at 15:58

baudsp

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answered Nov 10, 2016 at 15:00

InTheDark

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Comments

wookiee · Accepted Answer · 2016-11-10 14:55:11Z

0

I just created a simple console application with your final nested if statement and it worked fine

Sub Main()
    Dim a = False
    Dim b = True
    If a Then
        If b Then
            Console.WriteLine("A & B")
        End If
    Else
        Console.WriteLine("A & Not B")
    End If
    Console.ReadLine()
End Sub

answered Nov 10, 2016 at 14:55

wookiee

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1 Comment

Martin Verjans Over a year ago

I know this would work, I am asking if it's possible to do that in an inline statement.

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