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POSequential Guid Generator
 

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    <p>Is there any way to get the functionality of the Sql Server 2005+ Sequential Guid generator without inserting records to read it back on round trip or invoking a native win dll call? I saw someone answer with a way of using rpcrt4.dll but I'm not sure if that would be able to work from my hosted environment for production.</p> <p><strong>Edit:</strong> Working with @John Boker's answer I attempted to turn it into more of a GuidComb generator instead of being dependent on the last generated Guid other than starting over. That for the seed instead of starting with Guid.Empty that I use</p> <pre><code>public SequentialGuid() { var tempGuid = Guid.NewGuid(); var bytes = tempGuid.ToByteArray(); var time = DateTime.Now; bytes[3] = (byte) time.Year; bytes[2] = (byte) time.Month; bytes[1] = (byte) time.Day; bytes[0] = (byte) time.Hour; bytes[5] = (byte) time.Minute; bytes[4] = (byte) time.Second; CurrentGuid = new Guid(bytes); } </code></pre> <p>I based that off the comments on</p> <pre><code>// 3 - the least significant byte in Guid ByteArray [for SQL Server ORDER BY clause] // 10 - the most significant byte in Guid ByteArray [for SQL Server ORDERY BY clause] SqlOrderMap = new[] {3, 2, 1, 0, 5, 4, 7, 6, 9, 8, 15, 14, 13, 12, 11, 10}; </code></pre> <p>Does this look like the way I'd want to seed a guid with the DateTime or does it look like I should do it in reverse and work backwards from the end of the SqlOrderMap indexes? I'm not too concerned about their being a paging break anytime an initial guid would be created since it would only occur during application recycles.</p>
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    1. COIn what way is your proposed solution 'sequential', given that it will call NewGuid() every time to construct the base? What are you actually trying to do?
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    2. COAh - just read @John Boker's linked article; now it all makes sense... however won't your code produce two possibly non-sequential GUIDs if run twice within 1 second? (Because the parts of NewGuid() that you don't change may not change sequentially).
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    3. COThey would still be sequential, but one could possibly be lower than the other. The order doesn't matter because a clustered index will order them low to high (or something similarly) anyway.
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