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

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/utilities/convertcsharptovb.aspx.
It seems it handles these statements correctly.

Note that replacing "?" with IIf (which is what the free converters do) is
not correct.
The correct conversion is if/else.
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..Net Sports wrote:
It has been a very long time since I've done any VB programming so
please check my work.  But that should convert to something like this.

dim PurchaseType As String
dim Selections As XmlNodeList

If drwData["DailyItem"].ToString() = "True" Then
   PurchaseType = "ID"
Else
   PurchaseType = "PID"
End If



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

Hope that helps,

I would recommend Sean's solution as well.

if you really want to single-line it, you can always use the iif function:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vblr7/html/vafctiif.asp

Karl

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"Karl Seguin [MVP]" <karl REMOVE @ REMOVE openmymind REMOVEMETOO . ANDME
net> schrieb:
ACK, but note that all parameters are evaluated in the 'IIf' function.

Karl,
For VS 2005 code I would recommend my generic IIf over the VB.IIf as the
generic IIf is type safe.

http://www.tsbradley.net/Cookbook/Generics/genericIIf.aspx

As Herfried points out, my generic IIf & VB.IIf are both functions all
parameters are evaluated, meaning there may be subtle side effects, if you
are simply passing constants for the truePart & falsePart parameters, then
the fact IIf is a function wouldn't matter... If the parameters are function
calls then this may matter...


http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vblr7/html/vafctiif.asp
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Karl,

Why to obfuscate it to prevent maintenance?

I go for the solution from Sean

Cor

So would I, and that's why I'm recommending it, but I did want to make all
options known.

Thanks to both Herfried and Jay for pointing out the implications of IIF,
which I wasn't aware of and should certainly be taken into account.

Karl

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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.


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(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

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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.

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:

One of my favourite quotes; another from my top 10 (also from Michael S):

Marc

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

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!

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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.




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Don't minimize the issue -- function calls are not the only constructs with
side effects.

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