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Editorial Team
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Asked: 2026-05-14T08:59:21+00:00

My app interacts with both Oracle and SQL Server databases using a custom data

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My app interacts with both Oracle and SQL Server databases using a custom data access layer written in ADO.NET using DataReaders. Right now I’m having a problem with the conversion between GUIDs (which we use for primary keys) and the Oracle RAW datatype. Inserts into oracle are fine (I just use the ToByteArray() method on System.Guid). The problem is converting back to System.Guid when I load records from the database. Currently, I’m using the byte array I get from ADO.NET to pass into the constructor for System.Guid. This appears to be working, but the Guids that appear in the database do not correspond to the Guids I’m generating in this manner.

I can’t change the database schema or the query (since it’s reused for SQL Server). I need code to convert the byte array from Oracle into the correct Guid.

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  1. Editorial Team

    It turns out that the issue was the byte order you get in Guid.ToByteArray() and not Oracle itself. If you take the Guid “11223344-5566-7788-9900-aabbccddeeff” and call ToByteArray() on it, you get “44332211665588779900AABBCCDDEEFF“. If you then pass that byte array back into the constructor for Guid, you get the original Guid. My mistake was trying to query the Oracle database by the original Guid format (with the dashes removed) instead of the result of the ToByteArray() call.

    I still have no idea why the bytes are ordered that way, but it apparently has nothing to do with Oracle.

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