[VB.NET] cVar = ""

  • Thread starter Thread starter Alexander Vasilevsky
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A

Alexander Vasilevsky

What is equivalent to C #, this tool please?
What is this "" when assigning a variable of type Char?

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Alexander Vasilevsky said:
What is equivalent to C #, this tool please?
What is this "" when assigning a variable of type Char?
Click to expand...

\\\
Dim c As Char = ""
MsgBox(AscW(c)) ' 0.
///

BTW, this does not work with 'Option Strict On'.

C# equivalent: 'char x = '\0';'.
 
As some additional background information to Herfried's answer, there are 3
ways (that I know of) to 'clear' a Char variable:
c = Nothing
c = New Char()
c = ""

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Alexander said:
What is equivalent to C #, this tool please?
Click to expand...

I'm not really sure what you are asking about, so I will just answer
what I think that you are asking about...

A character literal is written using a C suffix in VB:

Dim c As Char = "p"C
What is this "" when assigning a variable of type Char?
Click to expand...

A Char value can not be an empty string. It's always exactly one
character, never more, never less.

(Well, to be accurate, Unicode has surrogate pairs and combining
characters, so to represent a complete character you may sometimes need
more than one Char value.)
 
Regardless of what should be allowed, VB regards "" as a legitimate char
assignment or comparison - and equivalent to "new Char()" or "Nothing" (note:
'Nothing' in VB means default value of the type and is not limited to
reference types).
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David said:
Regardless of what should be allowed, VB regards "" as a legitimate char
assignment
Click to expand...

Only if strict checking is disabled.
or comparison
Click to expand...

No, actually a Char will not be compared to "". The Char will be
converted to a string, and the string will be compared to "".

So, if you assign an empty string to a Char and then compare it to an
empty string, the comparison will give a False result:

DIm c As Char = ""
If c = "" Then
' will not get here
End If
- and equivalent to "new Char()" or "Nothing" (note:
'Nothing' in VB means default value of the type and is not limited to
reference types).
Click to expand...

Using New Char() actually creates slightly different code, but the same
result. It will create a temporary Char variable, initialise it, and
copy it to your Char variable.
 
You're right - good catch on the comparison issue - I just assumed that since
the assignment was allowed (without Option Strict On), that the comparison
would also be allowed.
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David Anton said:
As some additional background information to Herfried's answer, there are
3
ways (that I know of) to 'clear' a Char variable:
c = Nothing
c = New Char()
c = ""
Click to expand...

'c = ControlChars.NullChar', 'c = vbNullChar', 'c = ChrW(0)', ...

;-)
 
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