HOWTO: Use CoCreateGUID API to Generate a GUID with VB

• Microsoft Visual Basic Control Creation, Learning, Professional, and Enterprise Editions for Windows, versions 5.0, 6.0
• Microsoft Visual Basic Standard, Professional, and Enterprise Editions, 32-bit only, for Windows, version 4.0

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, Windows 98, 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. Add a Command Button to the form, and add the following code to the form:

   
         Private Sub Command1_Click()
              MsgBox GetGuid
         End Sub
    




4. Press F5 to run the project, and click the Command Button.

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