Visual Studio 2026 XmlDocument not found

[uholeschak]

I am using the NuGet Package CodegenCS.SourceGenerator 3.5.2, this is working well with VS 2022 and XmlDocument in the .csx files:

#r "System.Xml.dll"
#r "System.Xml.ReaderWriter.dll"
// Requires CodegenCS.SourceGenerator NuGet package
using CodegenCS.Runtime;
using Newtonsoft.Json;
using System.IO;
using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using System.Xml;
using System.Reflection;

public class UserTemplate
{
...
    async Task<bool> GenerateConfig(ICodegenTextWriter writer, ICodegenTextWriter logWriter)
    {
        string prefix = string.Empty;
        string key = string.Empty;

        try
        {
            string fileName = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.UserProfile), ".apk", "ionos_dns.xml");
            if (File.Exists(fileName))
            {
                XmlDocument doc = new XmlDocument();
                doc.Load(fileName);
                XmlNode nodeDns = doc.SelectSingleNode("/dns_info/api");
                if (nodeDns != null)
                {
                    XmlAttribute attribPrefix = nodeDns.Attributes["prefix"];
                    if (attribPrefix != null)
                    {
                        prefix = attribPrefix.Value;
                        logWriter.WriteLine($"Api: Prefix={prefix}");
                    }
                    XmlAttribute attribKey = nodeDns.Attributes["key"];
                    if (attribKey != null)
                    {
                        key = attribKey.Value;
                        logWriter.WriteLine($"Api: Key={key}");
                    }
                }
            }
            else
            {
                logWriter.WriteLine($"Configuration file not found: {fileName}");
            }
        }
        catch (Exception ex)
        {
            logWriter.WriteLine($"Exception: {ex.Message}");
            return false;
        }
...
}

When using it with VS2026 I get the error message:
1>CSC : error CODEGENCS002: Failed to build CodegenCS Template 'User.csx' (line 64 column 17): 'Der Typname "XmlDocument" konnte nicht im Namespace "System.Xml" gefunden werden. Dieser Typ wurde an Assembly "System.Xml.ReaderWriter, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" weitergeleitet. Sie sollten einen Verweis auf die Assembly hinzufügen.'
Is this simply not compatible with VS2026 or is a different #r command required?

[uholeschak]

After installing VS 2026 this is now also failing in VS 2022 with the same error message. Ist seem that there are "shared" components ...
At the moment I have switched to the command line tool to fix the problem and uninstalled the NuGet package.

set "CodegenCs=%USERPROFILE%\.dotnet\tools\dotnet-codegencs.exe"
!CodegenCs!  template run "$(ProjectDir)User" -r:System.Xml.dll -r:System.Xml.ReaderWriter.dll -r:System.Private.Xml.dll --OutputFolder "!OutputDir!"