Can't save XDocument into Application Settings class

Question

I'm trying to use IXmlSerializable ReadXml and WriteXml methods with an XDocument object ( using the Foo.WriteTo( ... ) and XDocument.Load( ... ) methods.

I want to store the class which implements the IXmlSerializable interface into a variable stored within the default Application Settings class.

Trying to do this results in a pretty obnoxious failure :

This is the Settings class :

This is the class wrapping the

[Serializable]
class XmlModel : IXmlSerializable {
    public XDocument _foo = new XDocument(
        new XElement( "Foo",
            new XElement( "Bar", "Baz" ) ) );

    public XmlModel( XDocument Foo ) {
        _foo = Foo;
    }

    public XmlSchema GetSchema( ) {
        return null;
    }

    public void ReadXml( XmlReader reader ) {
        this._foo = XDocument.Load( reader );
    }

    public void WriteXml( XmlWriter writer ) {
        _foo.WriteTo( writer );
    }
}

Aaaand this is the Program class ( I'm using just a simple console application to reproduce the issue )

class Program {
    static void Main( string[ ] args ) {
        if ( Settings.Default.DoUpgrade ) {
            Settings.Default.Upgrade( );
            Settings.Default.DoUpgrade = false;
            Settings.Default.Save( );
        }
        Console.WriteLine( Settings.Default.Foo._foo );
        Console.ReadLine( );
    }
}

This exception pops up because I have all exceptions turned on, but even with them OFF, the ApplicationSettings file isn't taking the data.

Why is this happening?

Do you have to store such complex data in Settings? Why not use self-defined config file instead? — Lei Yang, Dec 13 '16 at 01:14
@LeiYang I'd rather keep the class within the application settings. It's how I've done it until now ( except for a change wherein the underlying data used to be stored separately but now is all stored in a single XDocument ). I don't know any better way to create an application config. — Will, Dec 13 '16 at 01:30

Will · Answer 1 · 2016-12-14T20:51:24.580

I found the answer, and Lei Yang was correct ( at least in the sense that I can't use XDocuments with Application Settings ).

According to the docs...

    /// <summary>
    /// Output this <see cref="XElement"/> to an <see cref="XmlWriter"/>.
    /// </summary>
    /// <param name="writer">
    /// The <see cref="XmlWriter"/> to output the XML to.
    /// </param>
    public void Save(XmlWriter writer) {
        if (writer == null) throw new ArgumentNullException("writer");
        writer.WriteStartDocument();
        WriteTo(writer);
        writer.WriteEndDocument();
    }

XDocument.Save( ) calls writer.WriteStartDocument( ), which is apparently called further up in the ApplicationSettings.Save( ) method, and since XDocument.Save( ... ) cannot be overridden, I ( and by extension, everyone else who tried this ) will have to find another way.

EDIT

Using an XElement instead of an XDocument allows it to be saved into an ApplicationSettings class :

[Serializable]
class XmlModel : IXmlSerializable {
    public XElement _foo = new XElement(
        "Foo", new XElement( "Bar", "Baz" ) );

    public XmlModel( XElement Foo ) {
        _foo = Foo;
    }

    public XmlSchema GetSchema( ) {
        return null;
    }

    public void ReadXml( XmlReader reader ) {
        this._foo = XElement.Load( reader );
    }

    public void WriteXml( XmlWriter writer ) {
        _foo.WriteTo( writer );
    }
}

Can't save XDocument into Application Settings class

1 Answers1

EDIT