How to Determine If a String Is UNICODE or ANSI (138142)


The information in this article applies to:

  • Microsoft Visual Basic Standard Edition, 32-bit, for Windows 4.0
  • Microsoft Visual Basic Professional Edition, 16-bit, for Windows 4.0
  • Microsoft Visual Basic Professional Edition, 32-bit, for Windows 4.0
  • Microsoft Visual Basic Enterprise Edition, 16-bit, for Windows 4.0
  • Microsoft Visual Basic Enterprise Edition, 32-bit, for Windows 4.0
This article was previously published under Q138142

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.
Modification Type:MajorLast Reviewed:12/9/2003
Keywords:KB138142
©2003 Microsoft Corporation. All rights reserved.