I have a sample xml structure like:

<?xml version="1.0" encoding="iso-8859-1" ?>
<!DOCTYPE nzb PUBLIC "-//newzBin//DTD NZB 1.0//EN" "http://www.newzbin.com/DTD/nzb/nzb-1.0.dtd">
<nzb xmlns="http://www.newzbin.com/DTD/2003/nzb">
   <file...>
   </file>
   <file...>
   </file>
</nzb>

and .NET classes:

 [XmlRoot(ElementName = "nzb")]
 [XmlType("nzb")]
 public class Nzb
 {
     [XmlElement(ElementName = "file")]
     public FileData[] Files { get; set; } = [];
 }

 [XmlRoot(ElementName = "file")]
 public class FileData
 {
 }

and I tried:

XmlSerializer serializer = new XmlSerializer(typeof(Nzb));
Nzb? obj = null;

using TextReader reader = new StringReader(File.ReadAllText(file));
obj = (Nzb)serializer.Deserialize(reader);

There is no way to get rid of namespace that can be different. I tried from here Error Deserializing Xml to Object – xmlns=” was not expected but still no success for my case.