How can I generate UUID in C#
I am creating an .idl file programmatically. How do I create UUIDs for the interfaces and Methods Programmatically.
Can I generate the UUID programmatically?
Solution 1:
You are probably looking for System.Guid.NewGuid()
.
Solution 2:
Be careful: while the string representations for .NET Guid and (RFC4122) UUID are identical, the storage format is not. .NET trades in little-endian bytes for the first three Guid
parts.
If you are transmitting the bytes (for example, as base64), you can't just use Guid.ToByteArray()
and encode it. You'll need to Array.Reverse
the first three parts (Data1-3).
I do it this way:
var rfc4122bytes = Convert.FromBase64String("aguidthatIgotonthewire==");
Array.Reverse(rfc4122bytes,0,4);
Array.Reverse(rfc4122bytes,4,2);
Array.Reverse(rfc4122bytes,6,2);
var guid = new Guid(rfc4122bytes);
See this answer for the specific .NET implementation details.
Edit: Thanks to Jeff Walker, Code Ranger, for pointing out that the internals are not relevant to the format of the byte array that goes in and out of the byte-array constructor and ToByteArray()
.
Solution 3:
Here is a client side "sequential guid" solution.
http://www.pinvoke.net/default.aspx/rpcrt4.uuidcreate
using System;
using System.Runtime.InteropServices;
namespace MyCompany.MyTechnology.Framework.CrossDomain.GuidExtend
{
public static class Guid
{
/*
Original Reference for Code:
http://www.pinvoke.net/default.aspx/rpcrt4/UuidCreateSequential.html
*/
[DllImport("rpcrt4.dll", SetLastError = true)]
static extern int UuidCreateSequential(out System.Guid guid);
public static System.Guid NewGuid()
{
return CreateSequentialUuid();
}
public static System.Guid CreateSequentialUuid()
{
const int RPC_S_OK = 0;
System.Guid g;
int hr = UuidCreateSequential(out g);
if (hr != RPC_S_OK)
throw new ApplicationException("UuidCreateSequential failed: " + hr);
return g;
}
/*
Text From URL above:
UuidCreateSequential (rpcrt4)
Type a page name and press Enter. You'll jump to the page if it exists, or you can create it if it doesn't.
To create a page in a module other than rpcrt4, prefix the name with the module name and a period.
. Summary
Creates a new UUID
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
*/
}
}
Keywords: CreateSequentialUUID SequentialUUID