[RESOLVED] Null strings

[krtxmrtz]

I have read somewhere in the forums that this statement:

If myStr = "" Then

is less convenient (efficient?) than:

If myStr = vbNull Then

But I can't remember if the correct constant above is vbNull, vbNullChar, vbNullStr or what...

[Siddharth Rout]

I prefer

If Len(Trim(myStr)) = 0 then

[krtxmrtz]

I prefer

If Len(Trim(myStr)) = 0 then

Any special reason?

[si_the_geek]

The constant you want is vbNullString

It uses slightly less memory, and is slightly faster. Apparently the fastest way is to use LenB, eg:

If LenB(myStr) = 0 Then

[Siddharth Rout]

Sub Sample()
    Dim Strg As String
    
    Strg1 = ""
    Strg2 = " "
    
    '~~> If we look at it both strings are empty though the 2nd one has an empty space
    If Strg1 = vbNullString Then MsgBox "Sting 1 is Empty"
    
    If Len(Trim(Strg2)) = 0 Then MsgBox "Sting 2 is Empty"
End Sub

Edit: Sigh! Speedy Si at work

[krtxmrtz]

The constant you want is vbNullString

It uses slightly less memory, and is slightly faster. Apparently the fastest way is to use LenB, eg:

If LenB(myStr) = 0 Then

Thanks, I had tried with vbnullstr and was surprised that it was not acknowledged as a vb constant.

[krtxmrtz]

Sub Sample()
    Dim Strg As String
    
    Strg1 = ""
    Strg2 = " "
    
    '~~> If we look at it both strings are empty though the 2nd one has an empty space
    If Strg1 = vbNullString Then MsgBox "Sting 1 is Empty"
    
    If Len(Trim(Strg2)) = 0 Then MsgBox "Sting 2 is Empty"
End Sub

Edit: Sigh! Speedy Si at work

I see what you mean, but " " may or may not be considered an empty string, depending on the specific situation.

I started the thread because I wanted to prevent errors when reading a text file line-wise. If there was a vbcrlf at the end of the last non-empty line then a null string was read next.

[si_the_geek]

Thanks, I had tried with vbnullstr and was surprised that it was not acknowledged as a vb constant.

There's no need to remember (or type) the whole thing, because VB will happily tell you what they all are.. just type vbNu and press Ctrl-Space (and if you type vbNulls it will complete it for you).

[krtxmrtz]

There's no need to remember (or type) the whole thing, because VB will happily tell you what they all are.. just type vbNu and press Ctrl-Space (and if you type vbNulls it will complete it for you).

I always forget about ctrl/space. At any rate, I assume vbnull is for objects, but what would the difference be between vbnullchar and vbnullstring?

[si_the_geek]

vbNull is actually a number, for comparing with the result of (I think) the VarType function.

vbNullChar is the same as Chr$(0), but quicker because it is a constant rather than a function.

vbNullString is a string with a null pointer (which is needed for some API's), but within VB it is the equivalent of an empty string.