Q138142: How to Determine If a String Is UNICODE or ANSI

Article: Q138142
Product(s): Microsoft Visual Basic for Windows
Version(s): 
Operating System(s): 
Keyword(s): 
Last Modified: 11-JAN-2001

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The information in this article applies to:

- Microsoft Visual Basic Standard Edition, 32-bit, for Windows, version 4.0 
- Microsoft Visual Basic Professional Edition, 16-bit, for Windows, version 4.0 
- Microsoft Visual Basic Professional Edition, 32-bit, for Windows, version 4.0 
- Microsoft Visual Basic Enterprise Edition, 16-bit, for Windows, version 4.0 
- Microsoft Visual Basic Enterprise Edition, 32-bit, for Windows, version 4.0 
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SUMMARY
=======

ANSI strings use one byte per character if they don't contain any DBCS
characters. UNICODE strings use two bytes per character.

There is a built-in OLE API function that allows you determine whether a string
is UNICODE or ANSI. However, you can also use the Len() and LenB() Visual Basic
functions to compare the length of the string in characters and in bytes, as
demonstrated by the step-by-step example in this article.

NOTE: The code sample in this article will work only for those cases where you
are not likely to encounter DBCS characters in ANSI strings.

MORE INFORMATION
================

The Len function returns the length of the string in characters, and the LenB
function returns the length of the string in bytes. While this is the same for
an ANSI string, LenB will return a value twice that returned by Len for a
UNICODE string. This fact can be used to determine if a string is UNICODE or
ANSI.

NOTE: When a string has been brought into the Visual Basic environment, it will
be DBCS if it is the 16-bit version of the product, and UNICODE if it is the
32-bit version of the product. If the string is DBCS, then the string contains
characters that are either one or two bytes per character, depending on the
contents of the string and the language support in the Operating System. If you
do happen to be able to get a 32-bit string that contains the bit patterns for
ANSI/DBCS characters, it will be interpreted as UNICODE and produce invalid
results when manipulated or used because the UNICODE characters are definitely
not what you want.

Step-By-Step Example
--------------------

1. Start a new project in 32-bit Visual Basic. Form1 is created by default.

2. Add the following code to the General Declarations section of Form1:

     Private Function IsUnicode(s As String) As Boolean
        If Len(s) = LenB(s) Then
           IsUnicode = False
        Else
           IsUnicode = True
        End If
     End Function

3. Add the following code to the Form_Click event of Form1:

     Private Sub Form_Click()
        Dim s As String
        s = "hello"
        Debug.Print IsUnicode(s)
     End Sub

4. Press F5 to run the program. Click the form. The IsUnicode function will
  return True in the debug window. This is because 32-bit Visual Basic always
  stores UNICODE strings internally. If the same code is run under 16-bit
  Visual Basic, the IsUnicode Function will return False because 16-bit Visual
  Basic stores ANSI strings internally.

Additional query words: 4.00 vb4win vb4all

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Keywords          :  
Technology        : kbVBSearch kbAudDeveloper kbVB400Search kbVB400 kbVB16bitSearch

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