Monodroid: Document element did not appear

Question

I'm trying to deserialize an XML file to an object in my android application, developed with Xamarin Monodroid).

I generate my XML in pure C#, copy the XML file in the assets folder of the application, then deserialize it when the app starts.

[Serializable]
public class MyGreatObject
{
    public string ObjectName;
    public string ObjectLink;
    public string ObjectStuff;
    public List<OtherGreatObject> OtherObjects;

    public MyGreatObject()
    {
        OtherObjects = new List<OtherGreatObject>();
    }
}

The OtherGreaterObject has common attributes (string format I mean). So, I generate the XML and have something like this:

<?xml version="1.0" encoding="utf-8"?>
<MyGreatObject xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <ObjectName>This is the object name</ObjectName>
  <ObjectLink>http://www.xamarin-is-awesome.com</ObjectLink>
  <ObjectStuff>Description</ObjectStuff>
  <OtherObjects>
        <OtherGreatObject>...</OtherGreatObject>
        <OtherGreatObject>...</OtherGreatObject>
  </OtherObjects>
</MyGreatObject>

And I try to deserialize it like that:

internal static class SerializableXml
{
    public static MyGreatObject LoadData(Context context_, string fileName_)
    {
        MyGreatObject greatObject = new MyGreatObject();
        try
        {
            XmlSerializer xmlSerializer = new XmlSerializer(typeof(MyGreatObject));
            using (Stream input = context_.Assets.Open(fileName_, Android.Content.Res.Access.Buffer))
                greatObject = xmlSerializer.Deserialize(input) as MyGreatObject;
        }
        catch (Exception exception)
        {
            Android.Util.Log.Error("XML", "ERROR IN LOADING");
            Android.Util.Log.Error("XML", exception.ToString());
            throw;
        }
        return greatObject;
    }
}

But I get the error System.Xml.XmlException: Document element did not appear. Line 1, position 1. System.Xml.XmlException: Document element did not appear. Line 1, position 1. .

at Mono.Xml2.XmlTextReader.Read() [0x00000] in <filename unknown>:0
at System.Xml.XmlTextReader.Read() [0x00000] in <filename unknown>:0
at System.Xml.XmlReader.MoveToCOntent() [0x00000] in <filename unknown>:0
at System.Xml.Serialization.XmlSerializationReaderInterpreter.ReadRoot() [0x00000] in <filename unknown>:0
at System.Xml.Serialization.XmlSerializer.Deserialize(System.Xml.SerializationReader reader) [0x00000] in <filename unknown>:0

I lost plenty of time on Google, so I'm asking you.

Thanks a lot in advance for the help you can provide.

Answer 1

Well, problem resolved.

Google didn't find anything about the error (in my situation). I thought that the XmlSerializer (I read about an error in Mono Framework few years ago), but it wasn't.

Than, I thought that something was wrong in the XML, but wasn't sure at all. Why would I have such a error message ? I should have "Invalid node name", "Invalid attribute", or something like that.

But I was right. A node had a bad name , and this returns Document element did not appear. Line 1, position 1. Document element did not appear. Line 1, position 1. (or the exception message that means nothing at all) !

So, problem solved.

Answer 2

I came across this error as well using Xamarin.iOS 8.4 Even though on Android everything worked fine, on the iOS build I received the error:

Document element did not appear.  Line 1, position 1.

my XML file (which was not written manually, but serialized in c#) had the following line:

<?xml version="1.0" ?>

I fixed it by adding the encoding property as follows:

<?xml version="1.0" encoding="utf-8"?>

If you have many files, clearly this is not the best solution, but perhaps there is a method in the serializer that edits the encoding. I did not look into that since I did not need to, but if anyone comes across this issue, it may be a start.