NullReferenceException when deserializing a simple XML document

[Cédric Luthi]

I'm trying to deserialize a very simple XML document with ExtendedXmlSerializer but I'm getting a NullReferenceException.

Here's what I'm doing.

Issue580.csproj

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net6.0</TargetFramework>
    <Nullable>enable</Nullable>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="ExtendedXmlSerializer" Version="3.7.6" />
  </ItemGroup>

</Project>

Program.cs

using System;
using System.IO;
using System.Text;
using System.Xml.Serialization;
using ExtendedXmlSerializer;
using ExtendedXmlSerializer.Configuration;

const string xml = @"<?xml version=""1.0"" encoding=""utf-8""?>
<Customers>
  <Customer>
    <Name>Name1</Name>
  </Customer>
  <Customer>
    <Name>Name2</Name>
  </Customer>
</Customers>";
using var stream = new MemoryStream(Encoding.UTF8.GetBytes(xml));

var xmlSerializer = new XmlSerializer(typeof(Subject));
var extendedXmlSerializer = new ConfigurationContainer().EnableImplicitTypingFromNamespacePublic<Subject>().Create();

var subject = (Subject)xmlSerializer.Deserialize(stream)!;
Console.WriteLine(subject.Customers[1].Name);

stream.Position = 0;

subject = extendedXmlSerializer.Deserialize<Subject>(stream);
Console.WriteLine(subject.Customers[1].Name);

[XmlRoot("Customers")]
public class Subject
{
    [XmlElement("Customer")]
    public Customer[] Customers { get; init; } = Array.Empty<Customer>();
}

public class Customer
{
    [XmlElement("Name")]
    public string Name { get; init; } = "";
}

I'd expect the ExtendedXmlSerializer to deserialize the document but instead I'm getting this exception:

Unhandled exception. System.NullReferenceException: Object reference not set to an instance of an object.
   at ExtendedXmlSerializer.ReflectionModel.TypeCoercer.Get(TypeInfo parameter)
   at System.Linq.Enumerable.SelectArrayIterator`2.ToArray()
   at System.Linq.Enumerable.ToArray[TSource](IEnumerable`1 source)
   at System.Collections.Immutable.ImmutableArray.CreateRange[T](IEnumerable`1 items)
   at System.Collections.Immutable.ImmutableArray.ToImmutableArray[TSource](IEnumerable`1 items)
   at ExtendedXmlSerializer.ReflectionModel.SelectCoercer`2.Get(ImmutableArray`1 parameter)
   at ExtendedXmlSerializer.Core.Sources.CoercedResult`3.Get(TParameter parameter)
   at ExtendedXmlSerializer.Core.Sources.CoercedResult`3.Get(TParameter parameter)
   at ExtendedXmlSerializer.Core.Sources.CoercedResult`3.Get(TParameter parameter)
   at ExtendedXmlSerializer.Core.Sources.DecoratedSource`2.Get(TParameter parameter)
   at ExtendedXmlSerializer.ReflectionModel.Extensions.Get[T](IParameterizedSource`2 this, TypeInfo[] parameters)
   at ExtendedXmlSerializer.ContentModel.Collections.Lists.CreateAdapter(Object parameter)
   at ExtendedXmlSerializer.ContentModel.Collections.Lists.Create(Object parameter)
   at System.Runtime.CompilerServices.ConditionalWeakTable`2.GetValueLocked(TKey key, CreateValueCallback createValueCallback)
   at System.Runtime.CompilerServices.ConditionalWeakTable`2.GetValue(TKey key, CreateValueCallback createValueCallback)
   at ExtendedXmlSerializer.Core.Sources.ReferenceCacheBase`2.Get(TKey key)
   at ExtendedXmlSerializer.ExtensionModel.Xml.XmlListContentsActivator.Create(IFormatReader reader, Object instance, XmlContent content)
   at ExtendedXmlSerializer.ExtensionModel.Xml.XmlInnerContentActivator.Get(IFormatReader parameter)
   at ExtendedXmlSerializer.ContentModel.Content.InnerContentReader.Get(IFormatReader parameter)
   at ExtendedXmlSerializer.ContentModel.ReaderAdapter`1.Get(IFormatReader parameter)
   at ExtendedXmlSerializer.ContentModel.Collections.ArrayReader.Get(IFormatReader parameter)
   at ExtendedXmlSerializer.ContentModel.Members.Extensions.GetIfAssigned[T](IReader`1 this, IFormatReader reader)
   at ExtendedXmlSerializer.ContentModel.Serializer`1.Get(IFormatReader parameter)
   at ExtendedXmlSerializer.ContentModel.Members.MemberSerializer.Get(IFormatReader parameter)
   at ExtendedXmlSerializer.ContentModel.Members.MemberHandler.Handle(IInnerContent contents, IMemberSerializer member)
   at ExtendedXmlSerializer.ContentModel.Content.InnerContentServices.Handle(IInnerContent contents, IMemberSerializer member)
   at ExtendedXmlSerializer.ContentModel.Members.MemberInnerContentHandler.IsSatisfiedBy(IInnerContent parameter)
   at ExtendedXmlSerializer.ContentModel.Content.InnerContentReader.Get(IFormatReader parameter)
   at ExtendedXmlSerializer.ContentModel.Members.Extensions.GetIfAssigned[T](IReader`1 this, IFormatReader reader)
   at ExtendedXmlSerializer.ContentModel.Serializer`1.Get(IFormatReader parameter)
   at ExtendedXmlSerializer.ContentModel.SerializerAdapter`1.Get(IFormatReader parameter)
   at ExtendedXmlSerializer.ExtensionModel.Xml.Read.Get(XmlReader parameter)
   at ExtendedXmlSerializer.ExtensionModel.Xml.Serializer.Deserialize(XmlReader reader)
   at ExtendedXmlSerializer.ExtensionModel.Xml.ExtendedXmlSerializer.Deserialize(XmlReader reader)
   at ExtendedXmlSerializer.ExtensionMethodsForSerialization.Deserialize[T](IExtendedXmlSerializer this, XmlReaderSettings settings, Stream stream)
   at ExtendedXmlSerializer.ExtensionMethodsForSerialization.Deserialize[T](IExtendedXmlSerializer this, Stream stream)
   at Program.<Main>$(String[] args) in Program.cs:line 27

Note that deserializing with XmlSerializer works fine and prints Name2 as expected.

Am I misconfiguring the ExtendedXmlSerializer or am I not declaring my classes with the proper attributes? Or did I just uncovered a bug?

[Mike-E]

Hi @0xced thank you for writing in. Unfortunately, there are some incompatibilities with the traditional serializer and ExtendedXmlSerializer, and I believe this is captured in #461.

This is also listed in our known issues in our ReadMe:
https://github.com/ExtendedXmlSerializer/home#known-issues

However, if you feel this is a different issue from what is identified/listed above I can take a further look into this for you. 👍

GitHub

GitHub - ExtendedXmlSerializer/home: A configurable and eXtensible Xml serializer for .NET.

A configurable and eXtensible Xml serializer for .NET. - GitHub - ExtendedXmlSerializer/home: A configurable and eXtensible Xml serializer for .NET.

[Mike-E]

This appears to have been answered. Unfortunately, no further major work can be done on this project and it is essentially in maintenance mode. I am more than open to exploring pull requests if you (or anyone reading this) so wish to do so. If you have any further questions/comments, please reply, and we'll take it from there. Closing this for now.