DOCUMENT:Q176790  17-NOV-1997  [vbwin]
TITLE   :HOWTO: Use CoCreateGUID API to Generate a GUID with VB
PRODUCT :Microsoft Visual Basic for Windows
PROD/VER:WINDOWS:4.0,5.0
OPER/SYS:WINDOWS
KEYWORDS:vb432 VB4WIN vb5all vb5howto

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The information in this article applies to:

 - Microsoft Visual Basic Control Creation, Learning, Professional, and
   Enterprise Editions for Windows, version 5.0
 - Microsoft Visual Basic Standard, Professional, and Enterprise Editions,
   32-bit only, for Windows, version 4.0
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SUMMARY
=======

As a programmer, you may need to generate GUIDs (Globally Unique
Identifiers) for various purposes. This article describes how to generate a
GUID in Visual Basic using the CoCreateGuid API.

NOTE: The code in this article is not intended and cannot be used to create
or change a GUID automatically generated by Visual Basic for custom ActiveX
components. GUIDs automatically generated by Visual Basic cannot be
altered.

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

The code below can be used to create a GUID in Visual Basic. The code calls
the CoCreateGuid API found in OLE32.DLL on both Windows 95 and Windows NT.
In order to call the API correctly, a variable of type GUID must be passed.
This code creates a custom type, named GUID, with four parts that represent
the individual parts separated by dashes that you would see when viewing a
CLSID or GUID in the system registry. This code simply returns a GUID;
however, it can be modified to add the dashes if desired:

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

1. Add a standard module to a new Visual Basic project. Form1 is created by
   default.

2. Paste the code below into the code module:

      Option Explicit
   
      Type GUID
         Data1 As Long
         Data2 As Integer
         Data3 As Integer
         Data4(7) As Byte
      End Type
   
      Declare Function CoCreateGuid Lib "OLE32.DLL" (pGuid As GUID) _
              As Long
   
      Global Const S_OK = 0 ' return value from CoCreateGuid
   
      Function GetGUID() As String
   
        Dim lResult As Long
        Dim lguid As GUID
        Dim MyguidString As String
        Dim MyGuidString1 As String
        Dim MyGuidString2 As String
        Dim MyGuidString3 As String
        Dim DataLen As Integer
        Dim StringLen As Integer
        Dim i%
   
        On Error GoTo error_olemsg
   
        lResult = CoCreateGuid(lguid)
   
        If lResult = S_OK Then
   
           MyGuidString1 = Hex$(lguid.Data1)
           StringLen = Len(MyGuidString1)
           DataLen = Len(lguid.Data1)
           MyGuidString1 = LeadingZeros(2 * DataLen, StringLen) _
              & MyGuidString1 'First 4 bytes (8 hex digits)
   
           MyGuidString2 = Hex$(lguid.Data2)
           StringLen = Len(MyGuidString2)
           DataLen = Len(lguid.Data2)
           MyGuidString2 = LeadingZeros(2 * DataLen, StringLen) _
              & Trim$(MyGuidString2) 'Next 2 bytes (4 hex digits)
   
           MyGuidString3 = Hex$(lguid.Data3)
           StringLen = Len(MyGuidString3)
           DataLen = Len(lguid.Data3)
           MyGuidString3 = LeadingZeros(2 * DataLen, StringLen) _
              & Trim$(MyGuidString3) 'Next 2 bytes (4 hex digits)
   
           GetGUID = _
              MyGuidString1 & MyGuidString2 & MyGuidString3
   
           For i% = 0 To 7
              MyguidString = MyguidString & _
                   Format$(Hex$(lguid.Data4(i%)), "00")
           Next i%
   
           'MyGuidString contains last 8 bytes of Guid (16 hex digits)
           GetGUID = GetGUID & MyguidString
   
        Else
           GetGUID = "00000000" ' return zeros if function unsuccessful
        End If
   
        Exit Function
   
      error_olemsg:
         MsgBox "Error " & Str(Err) & ": " & Error$(Err)
         GetGUID = "00000000"
         Exit Function
   
      End Function
   
      Function LeadingZeros(ExpectedLen As Integer, ActualLen As Integer) _
          As String
         LeadingZeros = String$(ExpectedLen - ActualLen, "0")
      End Function

3. Note that calling GetGUID from code will now return a GUID.
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Keywords          : vb432 VB4WIN vb5all vb5howto
Version           : WINDOWS:4.0,5.0
Platform          : WINDOWS
Issue type        : kbhowto

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Copyright Microsoft Corporation 1997.