Process XML in C# using external entity file

Question

I am processing an XML file (which does not contain any dtd or ent declarations) in C# that contains entities such as é and à. I receive the following exception when attempting to load an XML file...

XmlDocument xmlDoc = new XmlDocument();
xmlDoc.LoadXml(record);

Reference to undeclared entity 'eacute'.

I was able to track down the proper ent file here. How do I tell XmlDocument to use this ent file when loading my XML file?

Answer 1

In versions of the framework prior to .Net 4 you use ProhibitDtd of an XmlReaderSettings instance.

var settings = new XmlReaderSettings();

settings.ProhibitDtd = false;

string DTD = @"<!DOCTYPE doc [
    <!ENTITY % iso-lat1 PUBLIC ""ISO 8879:1986//ENTITIES Added Latin 1//EN//XML""
    ""http://www.oasis-open.org/docbook/xmlcharent/0.3/iso-lat1.ent"">
    %iso-lat1;
    ]> ";

string xml = string.Concat(DTD,"<xml><txt>ren&eacute;</txt></xml>");

XmlDocument xd = new XmlDocument();
xd.Load(XmlReader.Create(new MemoryStream(
        UTF8Encoding.UTF8.GetBytes(xml)), settings));

From .Net 4.0 onward use the DtdProcessing property with a value of DtdProcessing.Parse which you set on the XmlTextReader.

XmlDocument xd = new XmlDocument();
using (var rdr = new XmlTextReader(new StringReader(xml)))
{
    rdr.DtdProcessing = DtdProcessing.Parse;
    xd.Load(rdr);
}