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CSharp · Console

/Program.cs

using System;
using System.IO;
using System.Xml.Serialization;
using System.Collections.Generic;

public class Program
{
	public static void Main()
	{
		string xml = "<?xml version=\"1.0\" encoding=\"utf-8\"?>" + 
"    <Objects>" + 
"       <Group index=\"1\">" + 
"           <de>" + 
"               <GroupName>ANTRIEB</GroupName>" + 
"           </de>" + 
"           <en>" + 
"               <GroupName>missing translation!</GroupName>" + 
"           </en>" + 
"           <Level>2</Level>" + 
"       </Group>" + 
"       <Group index=\"2\">" + 
"           <de>" + 
"               <GroupName>BREMSEN</GroupName>" + 
"           </de>" + 
"           <Level>3</Level>" + 
"       </Group>" + 
"    </Objects>";

	    XmlSerializer serializer = new XmlSerializer(typeof(DeactivationsXml));
        serializer.UnknownElement += Serializer_UnknownElement;
		
		DeactivationsXml result;
    	using (TextReader fileStream = new StringReader(xml))
    	{
        	result = (DeactivationsXml)serializer.Deserialize(fileStream);
    	}
		
		foreach (var group in result.Groups)
        {
            Console.WriteLine(group.Index);
            Console.WriteLine(group.Level);

            foreach (var name in group.GroupNames)
                Console.WriteLine(name.Key + ": " + name.Value.Name);
        }
	}
	
	private static void Serializer_UnknownElement(object sender, XmlElementEventArgs e)
    {
        var group = (DeactivationsGroup)e.ObjectBeingDeserialized;

        group.GroupNames.Add(e.Element.Name, new GroupName { Name = e.Element.InnerText });
    }
}

[XmlRoot("Objects")]
public class DeactivationsXml
{
    [XmlElement("Group")]
    public DeactivationsGroup[] Groups { get; set; }
}

public class DeactivationsGroup
{
    [XmlIgnore]
    public Dictionary<string, GroupName> GroupNames { get; set; } = new Dictionary<string, GroupName>();

    public int Level { get; set; }

    [XmlAttribute("index")]
    public byte Index { get; set; }
}

public class GroupName
{
    [XmlElement("GroupName")]
    public string Name { get; set; }
}