PRB: Len and LenB May Differ on Size of User-Defined Types (147668)


The information in this article applies to:

  • Microsoft Visual Basic Professional Edition for Windows 5.0
  • Microsoft Visual Basic Enterprise Edition for Windows 5.0
This article was previously published under Q147668

SYMPTOMS

When used with a user-defined type, the LenB function may return a different value than the Len function on 32-bit Windows platforms. This behavior occurs because the LenB function returns the in-memory size of a type, while the Len function returns the amount of size that a UDT would take if stored on disk. This occurs because Visual Basic 4.0 32-bit represents strings internally in Unicode, but externally (on disk) as ANSI. A string in the two-byte Unicode standard will occupy twice as much space as its ANSI equivalent.

STATUS

This behavior is by design.

MORE INFORMATION

The reproduction sample below demonstrates this behavior. Note that the fixed-length string is what causes different values for Len and LenB. The non-fixed-length string will always return a value of 4, because that is the space required to store a pointer to the location where the actual string is stored. The array of bytes of size five needs 5 bytes of storage, regardless of the contents of the array.

Steps to Reproduce

  1. Start a new Visual Basic 4.0 32-bit project. Form1 is created by default.
  2. Add a single module to the project by selecting Module from the Insert menu.
  3. Add this code to the General Declarations section of Module1: 
          Type MyUDT
         x As String * 5      'size of 10 or 5
         y As String       'size of 4
         z (1 to 5) As Byte   'size of 5
      End Type
  4. Add this code to the Form_Click event of Form1: 
          Private Sub Form_Click()
         Dim test As MyUDT

         test.x = "hello"
         test.y = "world"
         test.z(1) = 64
         test.z(2) = 65
         test.z(3) = 66
         test.z(4) = 67

         Print LenB(test)     'returns 21
         Print Len(test)      'returns 14
      End Sub
  5. Press the F5 key or select Start from the Run menu to run the application and observe the behavior.
Modification Type:MajorLast Reviewed:10/30/2003
Keywords:kb32bitOnly kbprb kbProgramming KB147668 kbAudDeveloper
©2003 Microsoft Corporation. All rights reserved.