Question

I’m working on an integration with a third party application that sends us an XML message. Their XML looks something like this:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE theirObj SYSTEM "theirDTD-2.0.dtd">
<theirObj>
    <properties>
        <datasource>ThirdParty</datasource>
        <datetime>2009-03-05T14:45:39</datetime>
    </properties>
        <data>
          ...
        </data>
</theirObj>

I’m trying to deserialize it using the XmlSerializer:

public theirObj Deserialize(string message) {
            if( string.IsNullOrWhiteSpace( message ) ) {
                throw new ArgumentNullException( "message" );
            }
            XmlSerializer xmlSerializer = new XmlSerializer( typeof(theirObj ) );

            TextReader textReader = new StringReader( message );

            using (XmlReader xmlReader = new XmlTextReader( textReader )) {
                object deserializedObject = xmlSerializer.Deserialize( xmlReader );

                theirObj ent = deserializedObject as theirObj ;

                if (ent == null) {
                    throw new InvalidCastException("Unable to cast deserialized object to an theirObj object. {0}".FormatInvariant( deserializedObject));
                }

                return ent;
            }
        }
}

I generated the objects using xsd.exe.

If I remove the <!DOCTYPE> tag then it deserializes fine.

Is there a way to get XmlSerializer to ignore the <!DOCTYPE> tag?

I know I could strip it out before passing it the XmlSerializer, but I’d rather not go to that level of XML manipulation if I don’t have to.

Answer 1

Instead of using XmlTextReader, call XmlReader.Create and pass it an XmlReaderSettings object with DtdProcessing set to Ignore:

TextReader textReader = new StringReader( message );
var settings = new XmlReaderSettings { DtdProcessing = DtdProcessing.Ignore };

using (XmlReader xmlReader = XmlReader.Create(textReader, settings))

Note: The DtdProcessing property was added in .NET 4.0. In .NET 3.5, you can instead set ProhibitDtd to false and XmlResolver to null:

var settings = new XmlReaderSettings { ProhibitDtd = false, XmlResolver = null };