Question

Consider the following unit test:

    [TestMethod]
    public void TestByteToString()
    {
        var guid = new Guid("61772f3ae5de5f4a8577eb1003c5c054");
        var guidString = guid.ToString("n");
        var byteString = ToHexString(guid.ToByteArray());

        Assert.AreEqual(guidString, byteString);
    }

    private String ToHexString(Byte[] bytes)
    {
        var hex = new StringBuilder(bytes.Length * 2);
        foreach(var b in bytes)
        {
            hex.AppendFormat("{0:x2}", b);
        }
        return hex.ToString();
    }

Here’s the result:

Assert.AreEqual failed. Expected:<61772f3ae5de5f4a8577eb1003c5c054>. Actual:<3a2f7761dee54a5f8577eb1003c5c054>.

Answer 1

Well, they are the same, after the first 4 bytes. And the first four are the same, just in the reverse order.

Basically, when created from the string, it’s assumed to be in “big-endian” format: Highest byte to the left. However, when stored internally (on an Intel-ish machine), the bytes are ordered “little-endian”: highest order byte to the right.