Empty string comparisons

[Neville Lang]

Hi all,

I am having a memory blank at the moment. I have been writing in C# for a
number of years and now need to do something in VB.NET, so forgive me such a
primitive question.

In C#, I test whether a string has a value or not by the following syntax:

if (thisString.Tri m() == "")
{
// if true
something()
}
else
{
// if false
somethingelse()
}

Now, in VB.NET an equivalent does not seem to work:

If thisString.Trim () = "" Then
' if true
something()
Else
' if false
somethingelse()
End If

I cannot get past a False return for the VB comparison. What is the best
method for testing whether a string is empty or null?


Regards,
Neville Lang

[Pritcham]

Re: Empty string comparisons

Hi Neville

Don't know whether this is 'best' or not but it certainly works:

If testStr Is Nothing or Len(Trim(testSt r)) = 0 Then
' 0 length or null string
Else
' string is initialised and not empty
End if

Cheers
Martin

Neville Lang wrote:

Hi all,
>
I am having a memory blank at the moment. I have been writing in C# for a
number of years and now need to do something in VB.NET, so forgive me such a
primitive question.
>
In C#, I test whether a string has a value or not by the following syntax:
>
if (thisString.Tri m() == "")
{
// if true
something()
}
else
{
// if false
somethingelse()
}
>
Now, in VB.NET an equivalent does not seem to work:
>
If thisString.Trim () = "" Then
' if true
something()
Else
' if false
somethingelse()
End If
>
I cannot get past a False return for the VB comparison. What is the best
method for testing whether a string is empty or null?
>
>
Regards,
Neville Lang

[tommaso.gastaldi@uniroma1.it]

Re: Empty string comparisons


Neville Lang ha scritto:

Now, in VB.NET an equivalent does not seem to work:
>
If thisString.Trim () = "" Then
' if true
something()
Else
' if false
somethingelse()
End If

I usually use:

Dim s As String = ""
If s.Trim = String.Empty Then
MsgBox("is empty")
Else
MsgBox("is not empty")
End If

but your version also looks fine to me (unless I am missing to see
something)...


Tommaso

>
I cannot get past a False return for the VB comparison. What is the best
method for testing whether a string is empty or null?
>
>
Regards,
Neville Lang

[David Anton]

RE: Empty string comparisons

Your problem probably lies elsewhere - the VB code you posted is the exact
equivalent to the C# code.
--
David Anton

https://www.tangiblesoftwaresolutions.com

Instant C#: VB to C# converter
Instant VB: C# to VB converter
Instant C++: C#/VB to C++ converter
Instant Python: VB to Python converter


"Neville Lang" wrote:

Hi all,
>
I am having a memory blank at the moment. I have been writing in C# for a
number of years and now need to do something in VB.NET, so forgive me such a
primitive question.
>
In C#, I test whether a string has a value or not by the following syntax:
>
if (thisString.Tri m() == "")
{
// if true
something()
}
else
{
// if false
somethingelse()
}
>
Now, in VB.NET an equivalent does not seem to work:
>
If thisString.Trim () = "" Then
' if true
something()
Else
' if false
somethingelse()
End If
>
I cannot get past a False return for the VB comparison. What is the best
method for testing whether a string is empty or null?
>
>
Regards,
Neville Lang
>
>
>

[Oenone]

Re: Empty string comparisons

Pritcham wrote:

Hi Neville
>
Don't know whether this is 'best' or not but it certainly works:
>
If testStr Is Nothing or Len(Trim(testSt r)) = 0 Then
' 0 length or null string
Else
' string is initialised and not empty
End if

Just in case you're not aware, the Len() and Trim() functions understand
strings that are Nothing and treat them as empty strings (unlike
testStr.Length( ) or testStr.Trim(), which would obviously throw a
NullReferenceEx ception), so you can actually shorten this to:

\\\
If Len(Trim(testSt r)) = 0 Then
' 0 length or null string
Else
' string is initialised and not empty
End if
///

--

(O)enone

[Claes Bergefall]

Re: Empty string comparisons

The code you have should work just fine. There are other ways to do it as
well though:

1. Use the VB.NET "feature" that null and empty string are considered equal
when using the = operator, i.e the following statement:
If thisString = "" Then
returns true if thisString is either empty *or* null (beware, this does not
work in C#)
2. Use the new String.IsNullOr Empty method (requires .NET 2.0)

/claes

"Neville Lang" <neville@MAPS_O Nnjlsoftware.co mwrote in message
news:ucODy9$9GH A.3348@TK2MSFTN GP03.phx.gbl...

Hi all,
>
I am having a memory blank at the moment. I have been writing in C# for a
number of years and now need to do something in VB.NET, so forgive me such
a primitive question.
>
In C#, I test whether a string has a value or not by the following syntax:
>
if (thisString.Tri m() == "")
{
// if true
something()
}
else
{
// if false
somethingelse()
}
>
Now, in VB.NET an equivalent does not seem to work:
>
If thisString.Trim () = "" Then
' if true
something()
Else
' if false
somethingelse()
End If
>
I cannot get past a False return for the VB comparison. What is the best
method for testing whether a string is empty or null?
>
>
Regards,
Neville Lang
>
>

[David Anton]

Re: Empty string comparisons

Regarding your first point, VB is even stranger than that:
A string set to Nothng (or uninitialized) is regarded as equal to an empty
string, but an empty string is *not* regarded as equal to Nothing. C# is
consistent in this respect: a null string is a null string and an empty
string is an empty string.
--
David Anton

https://www.tangiblesoftwaresolutions.com

Instant C#: VB to C# converter
Instant VB: C# to VB converter
Instant C++: C#/VB to C++ converter
Instant Python: VB to Python converter


"Claes Bergefall" wrote:

The code you have should work just fine. There are other ways to do it as
well though:
>
1. Use the VB.NET "feature" that null and empty string are considered equal
when using the = operator, i.e the following statement:
If thisString = "" Then
returns true if thisString is either empty *or* null (beware, this does not
work in C#)
2. Use the new String.IsNullOr Empty method (requires .NET 2.0)
>
/claes
>
"Neville Lang" <neville@MAPS_O Nnjlsoftware.co mwrote in message
news:ucODy9$9GH A.3348@TK2MSFTN GP03.phx.gbl...

Hi all,

I am having a memory blank at the moment. I have been writing in C# for a
number of years and now need to do something in VB.NET, so forgive me such
a primitive question.

In C#, I test whether a string has a value or not by the following syntax:

if (thisString.Tri m() == "")
{
// if true
something()
}
else
{
// if false
somethingelse()
}

Now, in VB.NET an equivalent does not seem to work:

If thisString.Trim () = "" Then
' if true
something()
Else
' if false
somethingelse()
End If

I cannot get past a False return for the VB comparison. What is the best
method for testing whether a string is empty or null?


Regards,
Neville Lang

>
>
>

[Claes Bergefall]

Re: Empty string comparisons

Actually it does (at least in 2.0). All of the following evaluate to True:

Dim s1 As String = ""
Dim s2 As String = Nothing
Dim b1 As Boolean = (s1 = Nothing)
Dim b2 As Boolean = (s2 = Nothing)
Dim b3 As Boolean = (s1 = "")
Dim b4 As Boolean = (s2 = "")

You have to use String.Equals to distinguish between Nothing and an empty
string. Personally I find the VB.NET behaviour annoying and would prefer
that it worked the same as in C#

/claes

"David Anton" <DavidAnton@dis cussions.micros oft.comwrote in message
news:63186DF2-8DE7-4EA4-9927-D6A755AD4596@mi crosoft.com...

Regarding your first point, VB is even stranger than that:
A string set to Nothng (or uninitialized) is regarded as equal to an empty
string, but an empty string is *not* regarded as equal to Nothing. C# is
consistent in this respect: a null string is a null string and an empty
string is an empty string.
--
David Anton

https://www.tangiblesoftwaresolutions.com

Instant C#: VB to C# converter
Instant VB: C# to VB converter
Instant C++: C#/VB to C++ converter
Instant Python: VB to Python converter
>
>
"Claes Bergefall" wrote:
>

>The code you have should work just fine. There are other ways to do it as
>well though:
>>
>1. Use the VB.NET "feature" that null and empty string are considered
>equal
>when using the = operator, i.e the following statement:
>If thisString = "" Then
>returns true if thisString is either empty *or* null (beware, this does
>not
>work in C#)
>2. Use the new String.IsNullOr Empty method (requires .NET 2.0)
>>
> /claes
>>
>"Neville Lang" <neville@MAPS_O Nnjlsoftware.co mwrote in message
>news:ucODy9$9G HA.3348@TK2MSFT NGP03.phx.gbl.. .

Hi all,
>
I am having a memory blank at the moment. I have been writing in C# for
a
number of years and now need to do something in VB.NET, so forgive me
such
a primitive question.
>
In C#, I test whether a string has a value or not by the following
syntax:
>
if (thisString.Tri m() == "")
{
// if true
something()
}
else
{
// if false
somethingelse()
}
>
Now, in VB.NET an equivalent does not seem to work:
>
If thisString.Trim () = "" Then
' if true
something()
Else
' if false
somethingelse()
End If
>
I cannot get past a False return for the VB comparison. What is the
best
method for testing whether a string is empty or null?
>
>
Regards,
Neville Lang
>
>

>>
>>
>>

[Jay B. Harlow]

Re: Empty string comparisons

Claes,

You have to use String.Equals to distinguish between Nothing and an empty
string.

Close! ;-)

I would recommend using "Is" to distinguish between Nothing and an empty
string.

Dim b5 As Boolean = (s1 Is Nothing)
Dim b6 As Boolean = (s2 Is Nothing)

One might consider these two, however they won't always return true:

Dim b7 As Boolean = (s1 Is "")
Dim b8 As Boolean = (s2 Is "")

Depending on how s1 & s2 got to be an empty string will change what the last
two return.

For example:

s2 = " ".Trim()

Will cause (s2 Is "") to fail, as " ".Trim() returns a new string,
where as "" returns an interned string...

Remember that = does value equality ("" & Nothing) are considered to have
the same value.

Where as Is does reference equality ("", " ".Trim() & Nothing) are
distinct object references.

Personally I find the VB.NET behavior annoying and would prefer that it
worked the same as in C#

Most of the time I agree, there are times though where I prefer the C#
behavior.

--
Hope this helps
Jay B. Harlow
..NET Application Architect, Enthusiast, & Evangelist
T.S. Bradley - http://www.tsbradley.net


"Claes Bergefall" <louplou@nospam .nospamwrote in message
news:%23f6zIUQ% 23GHA.3644@TK2M SFTNGP02.phx.gb l...

Actually it does (at least in 2.0). All of the following evaluate to True:
>
Dim s1 As String = ""
Dim s2 As String = Nothing
Dim b1 As Boolean = (s1 = Nothing)
Dim b2 As Boolean = (s2 = Nothing)
Dim b3 As Boolean = (s1 = "")
Dim b4 As Boolean = (s2 = "")
>
You have to use String.Equals to distinguish between Nothing and an empty
string. Personally I find the VB.NET behaviour annoying and would prefer
that it worked the same as in C#
>
/claes
>
"David Anton" <DavidAnton@dis cussions.micros oft.comwrote in message
news:63186DF2-8DE7-4EA4-9927-D6A755AD4596@mi crosoft.com...

>Regarding your first point, VB is even stranger than that:
>A string set to Nothng (or uninitialized) is regarded as equal to an
>empty
>string, but an empty string is *not* regarded as equal to Nothing. C# is
>consistent in this respect: a null string is a null string and an empty
>string is an empty string.
>--
>David Anton
>www.tangiblesoftwaresolutions.com
>Instant C#: VB to C# converter
>Instant VB: C# to VB converter
>Instant C++: C#/VB to C++ converter
>Instant Python: VB to Python converter
>>
>>
>"Claes Bergefall" wrote:
>>

>>The code you have should work just fine. There are other ways to do it
>>as
>>well though:
>>>
>>1. Use the VB.NET "feature" that null and empty string are considered
>>equal
>>when using the = operator, i.e the following statement:
>>If thisString = "" Then
>>returns true if thisString is either empty *or* null (beware, this does
>>not
>>work in C#)
>>2. Use the new String.IsNullOr Empty method (requires .NET 2.0)
>>>
>> /claes
>>>
>>"Neville Lang" <neville@MAPS_O Nnjlsoftware.co mwrote in message
>>news:ucODy9$9 GHA.3348@TK2MSF TNGP03.phx.gbl. ..
>Hi all,
>>
>I am having a memory blank at the moment. I have been writing in C#
>for a
>number of years and now need to do something in VB.NET, so forgive me
>such
>a primitive question.
>>
>In C#, I test whether a string has a value or not by the following
>syntax:
>>
>if (thisString.Tri m() == "")
>{
> // if true
> something()
>}
>else
>{
> // if false
> somethingelse()
>}
>>
>Now, in VB.NET an equivalent does not seem to work:
>>
>If thisString.Trim () = "" Then
> ' if true
> something()
>Else
> ' if false
> somethingelse()
>End If
>>
>I cannot get past a False return for the VB comparison. What is the
>best
>method for testing whether a string is empty or null?
>>
>>
>Regards,
>Neville Lang
>>
>>
>>>
>>>
>>>

>
>

[David Anton]

Re: Empty string comparisons

Yes, but try:
Dim s1 As String = ""
Dim b1 As Boolean = (s1 Is Nothing)

b1 evaluates to false. Isn't VB fun?!
--
David Anton

https://www.tangiblesoftwaresolutions.com

Instant C#: VB to C# converter
Instant VB: C# to VB converter
Instant C++: C#/VB to C++ converter
Instant Python: VB to Python converter


"Claes Bergefall" wrote:

Actually it does (at least in 2.0). All of the following evaluate to True:
>
Dim s1 As String = ""
Dim s2 As String = Nothing
Dim b1 As Boolean = (s1 = Nothing)
Dim b2 As Boolean = (s2 = Nothing)
Dim b3 As Boolean = (s1 = "")
Dim b4 As Boolean = (s2 = "")
>
You have to use String.Equals to distinguish between Nothing and an empty
string. Personally I find the VB.NET behaviour annoying and would prefer
that it worked the same as in C#
>
/claes
>
"David Anton" <DavidAnton@dis cussions.micros oft.comwrote in message
news:63186DF2-8DE7-4EA4-9927-D6A755AD4596@mi crosoft.com...

Regarding your first point, VB is even stranger than that:
A string set to Nothng (or uninitialized) is regarded as equal to an empty
string, but an empty string is *not* regarded as equal to Nothing. C# is
consistent in this respect: a null string is a null string and an empty
string is an empty string.
--
David Anton

https://www.tangiblesoftwaresolutions.com

Instant C#: VB to C# converter
Instant VB: C# to VB converter
Instant C++: C#/VB to C++ converter
Instant Python: VB to Python converter


"Claes Bergefall" wrote:

The code you have should work just fine. There are other ways to do it as
well though:
>
1. Use the VB.NET "feature" that null and empty string are considered
equal
when using the = operator, i.e the following statement:
If thisString = "" Then
returns true if thisString is either empty *or* null (beware, this does
not
work in C#)
2. Use the new String.IsNullOr Empty method (requires .NET 2.0)
>
/claes
>
"Neville Lang" <neville@MAPS_O Nnjlsoftware.co mwrote in message
news:ucODy9$9GH A.3348@TK2MSFTN GP03.phx.gbl...
Hi all,

I am having a memory blank at the moment. I have been writing in C# for
a
number of years and now need to do something in VB.NET, so forgive me
such
a primitive question.

In C#, I test whether a string has a value or not by the following
syntax:

if (thisString.Tri m() == "")
{
// if true
something()
}
else
{
// if false
somethingelse()
}

Now, in VB.NET an equivalent does not seem to work:

If thisString.Trim () = "" Then
' if true
something()
Else
' if false
somethingelse()
End If

I cannot get past a False return for the VB comparison. What is the
best
method for testing whether a string is empty or null?


Regards,
Neville Lang


>
>
>

>
>
>

[Jay B. Harlow]

Re: Empty string comparisons

>Personally I find the VB.NET behavior annoying and would prefer that it

>worked the same as in C#

Most of the time I agree, there are times though where I prefer the C#
behavior.

Huh? (cringle nose).

That didn't come out right. :-) I meant most of the item I agree; Most of
the time I prefer the C# behavior. However there are times I like the VB
behavior...

--
Hope this helps
Jay B. Harlow
..NET Application Architect, Enthusiast, & Evangelist
T.S. Bradley - http://www.tsbradley.net


"Jay B. Harlow" <Jay_Harlow_MVP @tsbradley.netw rote in message
news:27A229FC-862A-47A5-8527-A2FDAD88773B@mi crosoft.com...

Claes,

>You have to use String.Equals to distinguish between Nothing and an empty
>string.

Close! ;-)
>
I would recommend using "Is" to distinguish between Nothing and an empty
string.
>

>Dim b5 As Boolean = (s1 Is Nothing)
>Dim b6 As Boolean = (s2 Is Nothing)

>
One might consider these two, however they won't always return true:
>

>Dim b7 As Boolean = (s1 Is "")
>Dim b8 As Boolean = (s2 Is "")

>
Depending on how s1 & s2 got to be an empty string will change what the
last two return.
>
For example:
>
s2 = " ".Trim()
>
Will cause (s2 Is "") to fail, as " ".Trim() returns a new string,
where as "" returns an interned string...
>
Remember that = does value equality ("" & Nothing) are considered to have
the same value.
>
Where as Is does reference equality ("", " ".Trim() & Nothing) are
distinct object references.
>

>Personally I find the VB.NET behavior annoying and would prefer that it
>worked the same as in C#

Most of the time I agree, there are times though where I prefer the C#
behavior.
>
--
Hope this helps
Jay B. Harlow
.NET Application Architect, Enthusiast, & Evangelist
T.S. Bradley - http://www.tsbradley.net
>
>
"Claes Bergefall" <louplou@nospam .nospamwrote in message
news:%23f6zIUQ% 23GHA.3644@TK2M SFTNGP02.phx.gb l...

>Actually it does (at least in 2.0). All of the following evaluate to
>True:
>>
>Dim s1 As String = ""
>Dim s2 As String = Nothing
>Dim b1 As Boolean = (s1 = Nothing)
>Dim b2 As Boolean = (s2 = Nothing)
>Dim b3 As Boolean = (s1 = "")
>Dim b4 As Boolean = (s2 = "")
>>
>You have to use String.Equals to distinguish between Nothing and an empty
>string. Personally I find the VB.NET behaviour annoying and would prefer
>that it worked the same as in C#
>>
> /claes
>>
>"David Anton" <DavidAnton@dis cussions.micros oft.comwrote in message
>news:63186DF 2-8DE7-4EA4-9927-D6A755AD4596@mi crosoft.com...

>>Regarding your first point, VB is even stranger than that:
>>A string set to Nothng (or uninitialized) is regarded as equal to an
>>empty
>>string, but an empty string is *not* regarded as equal to Nothing. C#
>>is
>>consistent in this respect: a null string is a null string and an empty
>>string is an empty string.
>>--
>>David Anton
>>www.tangiblesoftwaresolutions.com
>>Instant C#: VB to C# converter
>>Instant VB: C# to VB converter
>>Instant C++: C#/VB to C++ converter
>>Instant Python: VB to Python converter
>>>
>>>
>>"Claes Bergefall" wrote:
>>>
>>>The code you have should work just fine. There are other ways to do it
>>>as
>>>well though:
>>>>
>>>1. Use the VB.NET "feature" that null and empty string are considered
>>>equal
>>>when using the = operator, i.e the following statement:
>>>If thisString = "" Then
>>>returns true if thisString is either empty *or* null (beware, this does
>>>not
>>>work in C#)
>>>2. Use the new String.IsNullOr Empty method (requires .NET 2.0)
>>>>
>>> /claes
>>>>
>>>"Neville Lang" <neville@MAPS_O Nnjlsoftware.co mwrote in message
>>>news:ucODy9$ 9GHA.3348@TK2MS FTNGP03.phx.gbl ...
>>Hi all,
>>>
>>I am having a memory blank at the moment. I have been writing in C#
>>for a
>>number of years and now need to do something in VB.NET, so forgive me
>>such
>>a primitive question.
>>>
>>In C#, I test whether a string has a value or not by the following
>>syntax:
>>>
>>if (thisString.Tri m() == "")
>>{
>> // if true
>> something()
>>}
>>else
>>{
>> // if false
>> somethingelse()
>>}
>>>
>>Now, in VB.NET an equivalent does not seem to work:
>>>
>>If thisString.Trim () = "" Then
>> ' if true
>> something()
>>Else
>> ' if false
>> somethingelse()
>>End If
>>>
>>I cannot get past a False return for the VB comparison. What is the
>>best
>>method for testing whether a string is empty or null?
>>>
>>>
>>Regards,
>>Neville Lang
>>>
>>>
>>>>
>>>>
>>>>

>>
>>

>

[Neville Lang]

Re: Empty string comparisons

HI all,

Thank you for your replies, they were helpful. From what I thought was a
fairly basic question, the responses did yield some interesting things in VB
v C#.

Regards,
Neville Lang



"Neville Lang" <neville@MAPS_O Nnjlsoftware.co mwrote in message
news:ucODy9$9GH A.3348@TK2MSFTN GP03.phx.gbl...

Hi all,
>
I am having a memory blank at the moment. I have been writing in C# for a
number of years and now need to do something in VB.NET, so forgive me such
a primitive question.
>
In C#, I test whether a string has a value or not by the following syntax:
>
if (thisString.Tri m() == "")
{
// if true
something()
}
else
{
// if false
somethingelse()
}
>
Now, in VB.NET an equivalent does not seem to work:
>
If thisString.Trim () = "" Then
' if true
something()
Else
' if false
somethingelse()
End If
>
I cannot get past a False return for the VB comparison. What is the best
method for testing whether a string is empty or null?
>
>
Regards,
Neville Lang
>
>

[Neville Lang]

Re: Empty string comparisons

David,

To be fair on this question, there were some extra things that I did not
post in my example that would probably have affected the outcome. So, you
may be right in suspecting it might have been elsewhere. Here is the
complete picture:

Dim someError(259) As Byte
Dim thisString As String
Dim ret As Integer
....
....
' This function call is one located in a C++ DLL
' The someError argument had Marshaling setup as follows
' <MarshalAs(Unma nagedType.LPArr ay, SizeConst:=260) ByVal someError As
Byte()
ret = externalFunctio n(a, b, c, someError)
thisString = Encoding.ASCII. GetString((some Error)

' Now the string comparison. It was found that the
' string's return value was "" but its length was 260, and so all
' combinations of string comparison yielded a False in VB and
' that is why I asked my question.

It is from my Compact Framework experience in C# that I got into the habit
of setting up Byte arrays for returning error strings from external
functions in C++ DLLs, due to P/Invoke Marshaling restrictions in the
Compact Framework. And that is what I have continued here too.

After reading the various responses here, I feel I am now a bit more
knowledgeable on string comparisons.

Regards,
Neville Lang




"David Anton" <DavidAnton@dis cussions.micros oft.comwrote in message
news:59A9EAC7-EE03-42AF-8D43-EE26682AC303@mi crosoft.com...

Your problem probably lies elsewhere - the VB code you posted is the exact
equivalent to the C# code.
--
David Anton

https://www.tangiblesoftwaresolutions.com

Instant C#: VB to C# converter
Instant VB: C# to VB converter
Instant C++: C#/VB to C++ converter
Instant Python: VB to Python converter
>
>
"Neville Lang" wrote:
>

>Hi all,
>>
>I am having a memory blank at the moment. I have been writing in C# for a
>number of years and now need to do something in VB.NET, so forgive me
>such a
>primitive question.
>>
>In C#, I test whether a string has a value or not by the following
>syntax:
>>
>if (thisString.Tri m() == "")
>{
> // if true
> something()
>}
>else
>{
> // if false
> somethingelse()
>}
>>
>Now, in VB.NET an equivalent does not seem to work:
>>
>If thisString.Trim () = "" Then
> ' if true
> something()
>Else
> ' if false
> somethingelse()
>End If
>>
>I cannot get past a False return for the VB comparison. What is the best
>method for testing whether a string is empty or null?
>>
>>
>Regards,
>Neville Lang
>>
>>
>>

[JimmyKoolPantz]

Re: Empty string comparisons

There is a new declaration type of "Nullable" in vs2005 that I like to
use. For example:

Dim ThisString As Nullable(Of String) = Nothing


and when you want to check value of ThisString all you have to do is
use this syntax:

If ThisString.HasV alue = True Then
'Do Something
End If




Neville Lang wrote:

Hi all,
>
I am having a memory blank at the moment. I have been writing in C# for a
number of years and now need to do something in VB.NET, so forgive me such a
primitive question.
>
In C#, I test whether a string has a value or not by the following syntax:
>
if (thisString.Tri m() == "")
{
// if true
something()
}
else
{
// if false
somethingelse()
}
>
Now, in VB.NET an equivalent does not seem to work:
>
If thisString.Trim () = "" Then
' if true
something()
Else
' if false
somethingelse()
End If
>
I cannot get past a False return for the VB comparison. What is the best
method for testing whether a string is empty or null?
>
>
Regards,
Neville Lang

[Claes Bergefall]

Re: Empty string comparisons

Ahh, yes. The Is operator behaves different from the = operator.
VB is hilarious :-)

/claes

"David Anton" <DavidAnton@dis cussions.micros oft.comwrote in message
news:C21FAC70-9BA6-4FE4-A541-6C359ADD3EB4@mi crosoft.com...

Yes, but try:
Dim s1 As String = ""
Dim b1 As Boolean = (s1 Is Nothing)
>
b1 evaluates to false. Isn't VB fun?!
--
David Anton

https://www.tangiblesoftwaresolutions.com

Instant C#: VB to C# converter
Instant VB: C# to VB converter
Instant C++: C#/VB to C++ converter
Instant Python: VB to Python converter
>
>
"Claes Bergefall" wrote:
>

>Actually it does (at least in 2.0). All of the following evaluate to
>True:
>>
>Dim s1 As String = ""
>Dim s2 As String = Nothing
>Dim b1 As Boolean = (s1 = Nothing)
>Dim b2 As Boolean = (s2 = Nothing)
>Dim b3 As Boolean = (s1 = "")
>Dim b4 As Boolean = (s2 = "")
>>
>You have to use String.Equals to distinguish between Nothing and an empty
>string. Personally I find the VB.NET behaviour annoying and would prefer
>that it worked the same as in C#
>>
> /claes
>>
>"David Anton" <DavidAnton@dis cussions.micros oft.comwrote in message
>news:63186DF 2-8DE7-4EA4-9927-D6A755AD4596@mi crosoft.com...

Regarding your first point, VB is even stranger than that:
A string set to Nothng (or uninitialized) is regarded as equal to an
empty
string, but an empty string is *not* regarded as equal to Nothing. C#
is
consistent in this respect: a null string is a null string and an empty
string is an empty string.
--
David Anton

https://www.tangiblesoftwaresolutions.com

Instant C#: VB to C# converter
Instant VB: C# to VB converter
Instant C++: C#/VB to C++ converter
Instant Python: VB to Python converter
>
>
"Claes Bergefall" wrote:
>
>The code you have should work just fine. There are other ways to do it
>as
>well though:
>>
>1. Use the VB.NET "feature" that null and empty string are considered
>equal
>when using the = operator, i.e the following statement:
>If thisString = "" Then
>returns true if thisString is either empty *or* null (beware, this
>does
>not
>work in C#)
>2. Use the new String.IsNullOr Empty method (requires .NET 2.0)
>>
> /claes
>>
>"Neville Lang" <neville@MAPS_O Nnjlsoftware.co mwrote in message
>news:ucODy9$9G HA.3348@TK2MSFT NGP03.phx.gbl.. .
Hi all,
>
I am having a memory blank at the moment. I have been writing in C#
for
a
number of years and now need to do something in VB.NET, so forgive
me
such
a primitive question.
>
In C#, I test whether a string has a value or not by the following
syntax:
>
if (thisString.Tri m() == "")
{
// if true
something()
}
else
{
// if false
somethingelse()
}
>
Now, in VB.NET an equivalent does not seem to work:
>
If thisString.Trim () = "" Then
' if true
something()
Else
' if false
somethingelse()
End If
>
I cannot get past a False return for the VB comparison. What is the
best
method for testing whether a string is empty or null?
>
>
Regards,
Neville Lang
>
>
>>
>>
>>

>>
>>
>>