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C# byte[] to hex string conversion inconsistency with Guid

Posted on 2007-03-27
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Last Modified: 2008-01-09
I am trying to figure out why I am having inconsistencies converting byte[]'s to Guids / hex strings.

I have the following code:
            byte[] bytes = [A 32-bit byte array]
            string guid1 = ByteUtility.HexStringFromByteArray(bytes);
          string guid2 = new Guid(bytes).ToString("N");

what I will see is (i don't care about the casing - just the out of order of the first 16 chars):

guid1 = 9C1D55DB53FA3F45889D6DC114CABB6B
guid2 = db551d9cfa53453f889d6dc114cabb6b


Here is the method in question:

            public static string HexStringFromByteArray(byte[] bytes) {
                  string s = "";

                  foreach (byte b in bytes) {
                        s += string.Format("{0:X2}", b);
                  }

                  return s;
            }

thanks
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Question by:czue
2 Comments
 
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Accepted Solution

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dstanley9 earned 250 total points
ID: 18800947
A GUID is broken into 4 parts:  an Int32 (4 bytes) two Int16s (2 bytes) and 8 bytes.  So when you pass in a byte array, it treats the first three sections as big-endian byte arrays as follows:

9C1D55DB 53FA 3F45 88 9D 6D C1 14 CA BB 6B

and thus the guid constructor converts each section into the appropriate type (int32, int16, int16, byte[]) and goes from there.  So the bytes in the first three sections get reversed:

db551d9c fa53 453f 88 9d 6d c1 14 ca bb 6b

Notice that the pairs (bytes) are reversed in the first three sections.  

Where as your Hex2String method is just outputting strings one byte at a time

Hope that helps.
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Author Comment

by:czue
ID: 18801061
Makes perfect sense - thanks very much.
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