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C# to VB.net conversion for "?" conditionals

P: n/a
I need to convert some C# ?Conditionals over to vb.net (most likely in
vb.net using If..Then statements), but the C#2VBNETconverter by
KamalPatel isn't converting them:

string PurchaseType = (Convert.ToString(drwData["DailyItem"]) ==
"True") ? "ID" : "PID";

XmlNodeList Selections = xdcData.GetElementsByTagName((X == 0) ?
"Highlight" : "Selection");

TIA
NetSports

Jan 26 '06 #1
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11 Replies


P: n/a
Take a look at other converters. Free SharpDevelop from
http://www.icsharpcode.net/OpenSource/SD/ can do this. There is also
online version at
http://www.developerfusion.co.uk/uti...sharptovb.aspx.
It seems it handles these statements correctly.

--
Peter Macej
Helixoft - http://www.vbdocman.com
VBdocman - Automatic generator of technical documentation for VB, VB
..NET and ASP .NET code
Jan 26 '06 #2

P: n/a
Hi,

VB has similar function called IIF

<From MSDN>
Public Function IIf( _
ByVal Expression As Boolean, _
ByVal TruePart As Object, _
ByVal FalsePart As Object _
)

Keep in mind that this is a FUNCTION as oposed to C# ?:, which is operator.
What does it mean? This means that TruePart and FalsePart are passed as
parameter to the function and if they are emthods' return values sides are
going to be executed regardless of the value of the Expression. This might
lead to hard-to-discover semantic errors if calculations of the true-part
and/or false-part have side effects.
--
HTH
Stoitcho Goutsev (100)

".Net Sports" <ba********@cox.net> wrote in message
news:11*********************@g43g2000cwa.googlegro ups.com...
I need to convert some C# ?Conditionals over to vb.net (most likely in
vb.net using If..Then statements), but the C#2VBNETconverter by
KamalPatel isn't converting them:

string PurchaseType = (Convert.ToString(drwData["DailyItem"]) ==
"True") ? "ID" : "PID";

XmlNodeList Selections = xdcData.GetElementsByTagName((X == 0) ?
"Highlight" : "Selection");

TIA
NetSports

Jan 26 '06 #3

P: n/a
(You get what you pay for with free converters)

Our Instant VB demo edition gives:

Dim PurchaseType As String
If (Convert.ToString(drwData("DailyItem")) = "True") Then
PurchaseType = "ID"
Else
PurchaseType = "PID"
End If

Dim Selections As XmlNodeList
If (X = 0) Then
Selections = xdcData.GetElementsByTagName("Highlight")
Else
Selections = xdcData.GetElementsByTagName("Selection")
End If

--
David Anton
www.tangiblesoftwaresolutions.com
Instant C#: VB to C# converter
Instant VB: C# to VB converter
Instant C++: C# to C++ converter & VB to C++ converter
Instant J#: VB to J# converter

".Net Sports" wrote:
I need to convert some C# ?Conditionals over to vb.net (most likely in
vb.net using If..Then statements), but the C#2VBNETconverter by
KamalPatel isn't converting them:

string PurchaseType = (Convert.ToString(drwData["DailyItem"]) ==
"True") ? "ID" : "PID";

XmlNodeList Selections = xdcData.GetElementsByTagName((X == 0) ?
"Highlight" : "Selection");

TIA
NetSports

Jan 27 '06 #4

P: n/a
Note that replacing "?" with IIf (which is what the free converters do) is
not correct.
The correct conversion is if/else.
--
David Anton
www.tangiblesoftwaresolutions.com
Instant C#: VB to C# converter
Instant VB: C# to VB converter
Instant C++: C# to C++ converter & VB to C++ converter
Instant J#: VB to J# converter

"Peter Macej" wrote:
Take a look at other converters. Free SharpDevelop from
http://www.icsharpcode.net/OpenSource/SD/ can do this. There is also
online version at
http://www.developerfusion.co.uk/uti...sharptovb.aspx.
It seems it handles these statements correctly.

--
Peter Macej
Helixoft - http://www.vbdocman.com
VBdocman - Automatic generator of technical documentation for VB, VB
..NET and ASP .NET code

Jan 27 '06 #5

P: n/a
".Net Sports" <ba********@cox.net> wrote in message
news:11*********************@g43g2000cwa.googlegro ups.com...
I need to convert some C# ?Conditionals over to vb.net

string PurchaseType = (Convert.ToString(drwData["DailyItem"]) ==
"True") ? "ID" : "PID";


The direct equivalent of the "?" operator is Visual Basic's IIf function:

Dim PurchaseType As String _
= DirectCast( IIf( drwData.Item("DailyItem").Equals( "True" ) _
, "ID" _
, "PID" _
), String )

(line breaks for clarity(?) only)

HTH,
Phill W.
Jan 27 '06 #6

P: n/a
Yes... but no...

As David observed - the *correct* replacement is If / Else / End If

The difference is that IIf always evaluates both sides, where-as ? and the
If / Else / End If construct only evaluate the side appropriate based on the
logical test.

So yes, IIf looks very similar, but it doesn't work the same, and you could
end up running more methods than you want; bad if the two sides are
expensive functions (for example).

You get similar problems with short-circuiting boolean expressions - hence
VB.Net introducing the AndAlso / OrElse operators (not present in VB6).

Aside: to quote Michael S a while ago:
I think we should have the OrElse keyword in C#. But only as an empty
keyword to threaten the compiler:

myList.Add(myString) OrElse;

Or maybe it could be used to eat exceptions. Hey, that would be quite
handy sometimes.
One of my favourite quotes; another from my top 10 (also from Michael S):
Visual Basic Sucks So Hard It Bends Light.


Marc
Jan 27 '06 #7

P: n/a
> One of my favourite quotes; another from my top 10 (also from Michael S):

Visual Basic Sucks So Hard It Bends Light.

Marc


Never heard that before. Even though I don't like VB, after a comment
like that I feel sorry for it.

Scott
Jan 27 '06 #8

P: n/a
To be fair, the full post went into quite some justification; look in the
archives if you want to see them.

I didn't want to start (yet another) VB dissin' session, so I'll stop here
;-p

Marc
Jan 27 '06 #9

P: n/a
Phil,
If your on VS 2005, check out my generic IIf (link previously posted), you
can simplify your statement to:

| Dim PurchaseType As String _
| = IIf( drwData.Item("DailyItem").Equals( "True" ) _
| , "ID" _
| , "PID" _
| )

The above line is with Option Strict On! My generic IIf uses generics & type
inference to "create" a "IIf(boolean, String, String) As String" as needed
and call it, no ugly DirectCast needed, no boxing of value types. Totally
Option Strict On friendly!
Of course there may be side effects...

Consider the following:

' note we are explicitly setting the seed values in each case to
' ensure we get the same sequence of pseudo random numbers back.

Dim falseCounter As New Random(1)
Dim trueCounter As New Random(2)
Debug.WriteLine(IIf(True, trueCounter.Next(), falseCounter.Next()),
"true")
Debug.WriteLine(IIf(False, trueCounter.Next(), falseCounter.Next()),
"false")

In VB it displays:

true: 1655911537
false: 237820880

While in alleged direct equivalent in C#:

Random falseCounter = new Random(1);
Random trueCounter = new Random(2);
Debug.WriteLine(true ? trueCounter.Next() : falseCounter.Next(),
"true");
Debug.WriteLine(false ? trueCounter.Next() :
falseCounter.Next(), "false");

Displays:

true: 1655911537
false: 534011718
Notice that the second line doesn't match, this is because VB called the
falseCounter.Next function twice (once on each line), while C# only called
it once (only on the second line).

If instead of IIf we use the code that Sean gave:

Dim value As Integer
If True Then
value = trueCounter.Next()
Else
value = falseCounter.Next()
End If
Debug.WriteLine(value, "true")
If False Then
value = trueCounter.Next()
Else
value = falseCounter.Next()
End If
Debug.WriteLine(value, "false")

We then get the same results as C#:

true: 1655911537
false: 534011718

Consider what happens if instead of calling Random.Next() you are calling a
GetNextSequenceNumber function, that simply increments a counter & return
it,

id = IIf(sequenceAlreadyExists, theExistingSequence,
GetNextSequenceNumber())

For example you are creating records from some input source and if the
record doesn't have an ID you call GetNextSequenceNumber to assign a new
one. The above line in VB will cause gaps in the sequence number, as is
called for every "line" in the input source. Consider what happens if the
GetNextSequenceNumber() function is fairly expensive (performance, memory
pressure, network, other) to execute.

As I stated, in the case of constants like the OP & your example, using IIf
doesn't hurt, however I strongly recommend any one using IIf to understand
what it is actually doing!

--
Hope this helps
Jay [MVP - Outlook]
..NET Application Architect, Enthusiast, & Evangelist
T.S. Bradley - http://www.tsbradley.net
"Phill W." <p-***********@o-p-e-n.a-c.u-k> wrote in message
news:dr**********@yarrow.open.ac.uk...
| ".Net Sports" <ba********@cox.net> wrote in message
| news:11*********************@g43g2000cwa.googlegro ups.com...
| >I need to convert some C# ?Conditionals over to vb.net
| >
| > string PurchaseType = (Convert.ToString(drwData["DailyItem"]) ==
| > "True") ? "ID" : "PID";
|
| The direct equivalent of the "?" operator is Visual Basic's IIf function:
|
| Dim PurchaseType As String _
| = DirectCast( IIf( drwData.Item("DailyItem").Equals( "True" ) _
| , "ID" _
| , "PID" _
| ), String )
|
| (line breaks for clarity(?) only)
|
| HTH,
| Phill W.
|
|
Jan 27 '06 #10

P: n/a
All of you are making a huge deal of this. The auto converter is wrong IF
there are any function calls in the <true> or <false> sections of
<conditional> ? <true> : <false>

VB correct equivalent is

IF <conditional> Then
<true>
ELSE
<false>
END IF

Don't bother with IIF() function - it will screw you because is supposedly
evaluates both the true and false sections before deciding what to do.
IF/ELSE does not. IF/ELSE correctly evaluates only the needed section of
code.


".Net Sports" <ba********@cox.net> wrote in message
news:11*********************@g43g2000cwa.googlegro ups.com...
I need to convert some C# ?Conditionals over to vb.net (most likely in
vb.net using If..Then statements), but the C#2VBNETconverter by
KamalPatel isn't converting them:

string PurchaseType = (Convert.ToString(drwData["DailyItem"]) ==
"True") ? "ID" : "PID";

XmlNodeList Selections = xdcData.GetElementsByTagName((X == 0) ?
"Highlight" : "Selection");

TIA
NetSports

Jan 29 '06 #11

P: n/a
Don't minimize the issue -- function calls are not the only constructs with
side effects.

"ZenRhapsody" <no****@hotmail.com> wrote in message
news:%2****************@TK2MSFTNGP11.phx.gbl...
All of you are making a huge deal of this. The auto converter is wrong IF
there are any function calls in the <true> or <false> sections of
<conditional> ? <true> : <false>

VB correct equivalent is

IF <conditional> Then
<true>
ELSE
<false>
END IF

Don't bother with IIF() function - it will screw you because is supposedly
evaluates both the true and false sections before deciding what to do.
IF/ELSE does not. IF/ELSE correctly evaluates only the needed section of
code.


".Net Sports" <ba********@cox.net> wrote in message
news:11*********************@g43g2000cwa.googlegro ups.com...
I need to convert some C# ?Conditionals over to vb.net (most likely in
vb.net using If..Then statements), but the C#2VBNETconverter by
KamalPatel isn't converting them:

string PurchaseType = (Convert.ToString(drwData["DailyItem"]) ==
"True") ? "ID" : "PID";

XmlNodeList Selections = xdcData.GetElementsByTagName((X == 0) ?
"Highlight" : "Selection");

TIA
NetSports


Feb 3 '06 #12

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