XmlSerializer Error, bytes array, List and InvalidOperationException

Question

I found a weird behavior with XmlSerializer in C#, an someone help me? I want this XML in SOAP/MTOM, and I need the xop:Include outside any other XMLElement:

<Root xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
    <xop:Include href="cid:http://tempuri.org/1/635913361387292553" xmlns:xop="http://www.w3.org/2004/08/xop/include"/>
    <List>1</List>
    <List>2</List>
</Root>

Here my C# code:

public static void Main(string[] args)
{
    var simulatedFile = new byte[800];
    new Random().NextBytes(simulatedFile);
    var root = new Root {List = new List<string> {"1","2"}, Bytes = simulatedFile};

    XmlSerializer ser = new XmlSerializer(typeof(Root));
    using (var mtomInMemory = new MemoryStream())
    {
        using (var writer = XmlDictionaryWriter.CreateMtomWriter(mtomInMemory, Encoding.UTF8, int.MaxValue, string.Empty))
        {
            ser.Serialize(writer, root);
        }
        Console.WriteLine(Encoding.UTF8.GetString(mtomInMemory.ToArray()));
    }

    Console.Read();
}
public class Root
{
    [XmlText]
    public byte[] Bytes { get; set; }
    [XmlElement]
    public List<string> List { get; set; }
}

The Error I have is:

'System.InvalidOperationException' occurred in System.Xml.dll There was an error reflecting type 'Program.Root'. Cannot serialize object of type 'Program.Root'. Consider changing type of XmlText member 'Program.Root.Bytes' from System.Byte[] to string or string array.

But I need to let my Bytes array to contain file binary because with MTOM, it will be serialized by the CreateMtomWriter in base64 if the Length is less that 768 byte or in xop:Include if more than 768 bytes.

I want it to be encoded as a direct child of Root Element, not wrapped in any other Element.

If in the class Root, i put only the Bytes or the List property, it works perfectly, but if i put both, it does not.

Answer 1

From Microsoft: Thanks for reporting this issue. This is by design. The array of bytes cannot be text value. Please try to workaround this issue e.g. using string.