Unable to make it work in a setup where a library using this package is shared between .NET 9 and .NET 472 projects

[MarkKharitonov]

test.zip

Attached are the following files:

C:\work\test [master]> tree /f
Folder PATH listing for volume Windows
Volume serial number is 268C-52B1
C:.
│   .gitignore
│   Test.sln
│
├───Exe
│       Exe.csproj
│       Program.cs
│
└───Lib
        Extensions.cs
        Lib.csproj
        ToStringJsonConverter.cs

C:\work\test [master]>

The problem - the same code works in net472 and does not work in net9.0:

net472

C:\work\test [master]> Exe\bin\Debug\net472\Exe.exe
Hello World!
"Hello World!"
"Hello World!"
C:\work\test [master]>

net9.0

C:\work\test [master]> Exe\bin\Debug\net9.0\Exe.exe
Hello World!
"Hello World!"
Unhandled exception. System.TypeLoadException: Could not load type 'System.Buffers.ArrayBufferWriter`1' from assembly 'Utf8StringInterpolation, Version=1.3.2.0, Culture=neutral, PublicKeyToken=df4c250b14d82627'.
   at Lib.Extensions.GetString()
   at Exe.Program.LibraryTestObject.ToString() in C:\work\test\Exe\Program.cs:line 18
   at DFModuleEnum.UnitTests.ToStringJsonConverter.WriteJson(JsonWriter writer, Object value, JsonSerializer serializer) in C:\work\test\Lib\ToStringJsonConverter.cs:line 10
   at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeConvertable(JsonWriter writer, JsonConverter converter, Object value, JsonContract contract, JsonContainerContract collectionContract, JsonProperty containerProperty)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeValue(JsonWriter writer, Object value, JsonContract valueContract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerProperty)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.Serialize(JsonWriter jsonWriter, Object value, Type objectType)
   at Newtonsoft.Json.JsonSerializer.SerializeInternal(JsonWriter jsonWriter, Object value, Type objectType)
   at Newtonsoft.Json.JsonSerializer.Serialize(JsonWriter jsonWriter, Object value, Type objectType)
   at Newtonsoft.Json.JsonConvert.SerializeObjectInternal(Object value, Type type, JsonSerializer jsonSerializer)
   at Newtonsoft.Json.JsonConvert.SerializeObject(Object value, Type type, JsonSerializerSettings settings)
   at Newtonsoft.Json.JsonConvert.SerializeObject(Object value)
   at Exe.Program.Main() in C:\work\test\Exe\Program.cs:line 25
C:\work\test [master]>

Here is the full code:

.\Exe\Exe.csproj

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFrameworks>net9.0;net472</TargetFrameworks>
    <SuppressTfmSupportBuildWarnings>true</SuppressTfmSupportBuildWarnings>
    <LangVersion>latest</LangVersion>
  </PropertyGroup>
  <ItemGroup>
    <Compile Include="..\Lib\Extensions.cs" Link="Extensions.cs" />
    <ProjectReference Include="..\Lib\Lib.csproj" />
  </ItemGroup>
</Project>

.\Exe\Program.cs

using DFModuleEnum.UnitTests;
using Newtonsoft.Json;
using System;

namespace Exe;

public static class Program
{
    [JsonConverter(typeof(ToStringJsonConverter))]
    public class LocalTestObject
    {
        override public string ToString() => Extensions.GetString();
    }

    [JsonConverter(typeof(ToStringJsonConverter))]
    public class LibraryTestObject
    {
        override public string ToString() => Lib.Extensions.GetString();
    }

    public static void Main()
    {
        Console.WriteLine(Extensions.GetString());
        Console.WriteLine(JsonConvert.SerializeObject(new LocalTestObject()));
        Console.WriteLine(JsonConvert.SerializeObject(new LibraryTestObject()));
    }
}

.\Lib\Lib.csproj

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFrameworks>netstandard2.0</TargetFrameworks>
    <LangVersion>latest</LangVersion>
    <DefineConstants>LIBRARY</DefineConstants>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Utf8StringInterpolation" Version="1.3.2" />
        <PackageReference Include="Newtonsoft.Json" Version="13.0.3" />
  </ItemGroup>
</Project>

.\Lib\Extensions.cs

using Utf8StringInterpolation;

#if LIBRARY
namespace Lib;
#else
namespace Exe;
#endif

public static class Extensions
{
    public static string GetString()
    {
        using (var buffer = Utf8String.CreateWriter(out var zsb))
        {
            zsb.Append("Hello World!");
            zsb.Flush();
            return buffer.ToString();
        }
    }
}

.\Lib\ToStringJsonConverter.cs

using Newtonsoft.Json;
using System;

namespace DFModuleEnum.UnitTests;

public class ToStringJsonConverter : JsonConverter
{
    public override bool CanConvert(Type objectType) => true;

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer) => writer.WriteValue(value.ToString());

    public override bool CanRead => false;

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer) => throw new NotImplementedException();
}