How to fix missing namespace prefix in XML

The internals of XmlReader are ugly and undocumented. So this solution is like playing with fire.

What I propose is: a XmlTextReader that "adds" the missing namespace. You can feed directly this FixingXmlTextReader to a XDocument.Load() OR you can feed it to a XmlTextReader/XmlValidatingReader (they all have a constructor/Create that accept a XmlReader as a parameter)

public class FixingXmlTextReader : XmlTextReader
{
    public override string NamespaceURI
    {
        get
        {
            if (NodeType == XmlNodeType.Attribute && base.LocalName == "noNamespaceSchemaLocation")
            {
                return NameTable.Add("http://www.w3.org/2001/XMLSchema-instance");
            }

            return base.NamespaceURI;
        }
    }

    public override string Prefix
    {
        get
        {
            if (NodeType == XmlNodeType.Attribute && base.NamespaceURI == string.Empty && base.LocalName == "noNamespaceSchemaLocation")
            {
                return NameTable.Add("xsi");
            }

            return base.Prefix;
        }
    }

    public override string Name
    {
        get
        {
            if (NodeType == XmlNodeType.Attribute && base.NamespaceURI == string.Empty && base.LocalName == "noNamespaceSchemaLocation")
            {
                return NameTable.Add(Prefix + ":" + LocalName);
            }

            return base.Name;
        }
    }

    public override string GetAttribute(string localName, string namespaceURI)
    {
        if (localName == "noNamespaceSchemaLocation" && namespaceURI == "http://www.w3.org/2001/XMLSchema-instance")
        {
            namespaceURI = string.Empty;
        }

        return base.GetAttribute(localName, namespaceURI);
    }

    public override string GetAttribute(string name)
    {
        if (name == "xsi:noNamespaceSchemaLocation")
        {
            name = "noNamespaceSchemaLocation";
        }

        return base.GetAttribute(name);
    }

    // There are tons of constructors, take the ones you need
    public FixingXmlTextReader(Stream stream) : base(stream)
    {
    }

    public FixingXmlTextReader(TextReader input) : base(input)
    {
    }

    public FixingXmlTextReader(string url) : base(url)
    {
    }
}

Like:

using (var reader = new FixingXmlTextReader("XMLFile1.xml"))
using (var reader2 = XmlReader.Create(reader, new XmlReaderSettings
{
}))
{
    // Use the reader2!
}

or

using (var reader = new FixingXmlTextReader("XMLFile1.xml"))
{
    var xdoc = new XmlDocument();
    xdoc.Load(reader);
}