C# Signature:
[DllImport("rpcrt4.dll", SetLastError=true)]
static extern int UuidCreateSequential(out Guid guid);
VB Signature:
Declare Function UuidCreateSequential Lib "rpcrt4.dll" (ByRef id As Guid) As Integer
User-Defined Types:
None.
Notes:
Microsoft changed the UuidCreate function so it no longer uses the machine's MAC address as part of the UUID. Since CoCreateGuid calls UuidCreate to get its GUID, its output also changed. If you still like the GUIDs to be generated in sequential order (helpful for keeping a related group of GUIDs together in the system registry), you can use the UuidCreateSequential function.
CoCreateGuid generates random-looking GUIDs like these:
92E60A8A-2A99-4F53-9A71-AC69BD7E4D75
BB88FD63-DAC2-4B15-8ADF-1D502E64B92F
28F8800C-C804-4F0F-B6F1-24BFC4D4EE80
EBD133A6-6CF3-4ADA-B723-A8177B70D268
B10A35C0-F012-4EC1-9D24-3CC91D2B7122
UuidCreateSequential generates sequential GUIDs like these:
19F287B4-8830-11D9-8BFC-000CF1ADC5B7
19F287B5-8830-11D9-8BFC-000CF1ADC5B7
19F287B6-8830-11D9-8BFC-000CF1ADC5B7
19F287B7-8830-11D9-8BFC-000CF1ADC5B7
19F287B8-8830-11D9-8BFC-000CF1ADC5B7
Here is a summary of the differences in the output of UuidCreateSequential:
- The last six bytes reveal your MAC address
- Several GUIDs generated in a row are sequential
Tips & Tricks:
Please add some!
Sample Code in C#:
static Guid UuidCreateSequential()
{
const int RPC_S_OK = 0;
Guid g;
int hr = UuidCreateSequential(out g);
if (hr != RPC_S_OK)
throw new ApplicationException
("UuidCreateSequential failed: " + hr);
return g;
}
Sample Code in VB:
Sub Main()
Dim myId As Guid
Dim code As Integer
code = UuidCreateSequential(myId)
If code <> 0 Then
Console.WriteLine("UuidCreateSequential failed: {0}", code)
Else
Console.WriteLine(myId)
End If
End Sub
Alternative Managed API:
Do you know one? Please contribute it!
