by C.J. (13 Submissions)
Category: Windows API Call/Explanation
Compatability: Visual Basic 4.0 (32-bit)
Difficulty: Unknown Difficulty
Originally Published: Sun 24th January 1999
Date Added: Mon 8th February 2021
Rating: 
(1 Votes)
As a programmer, you may need to generate GUIDs (Globally Unique Identifiers) for various purposes. Here is how to generate a GUID in Visual
API Declarations
Data1 As Long
Data2 As Integer
Data3 As Integer
Data4(7) As Byte
End Type
Public Declare Function CoCreateGuid Lib "OLE32.DLL" (pGuid As GUID) As Long
Public Const S_OK = 0 ' return value from CoCreateGuid
VBcoders
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
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