Use xsltc.exe generated assembly (XSLT stylesheet) in .NET 6

Question

I have an XSLT stylesheet "Stylesheet.xsl" that i have compiled to a "Stylesheet.dll" using xsltc.exe

That DLL is included in my .NET 6 (<TargetFramework>net6.0</TargetFramework>) project and is used as follows:

var xslCompiledTransform = new XslCompiledTransform();
xslCompiledTransform.Load(typeof(Stylesheet));
// ↑ System.IO.FileNotFoundException: Could not load file or assembly 'System.Data.SqlXml, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'. The system cannot find the file specified.

xslCompiledTransform.Transform(@"..\..\..\input.xml", @"..\..\..\output.xml");

The Load method throws an FileNotFoundException with message "Could not load file or assembly 'System.Data.SqlXml, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'. The system cannot find the file specified."

The documentation on xsltc.exe says the following:

Script blocks are supported only in .NET Framework. They are not supported on .NET Core or .NET 5 or later.

This heavily imiplies that stylesheets compiled using xsltc.exe should work on .NET Core or .NET 5 or later (when no script blocks are use) but they don't in my test.

Does anyone know why stylesheets compiled using xsltc.exe do not work with .NET 6 and how to fix this?

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More details

I've added more details on what I tried below.

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Note that the stylesheet Stylesheet.xsl I use is very basic and uses no special functionality:

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:output indent="yes"/>
    <xsl:template match="/">
        <output>
            <xsl:for-each select="input/book">
                <booktitle>
                    <xsl:value-of select="@title" />
                </booktitle>
            </xsl:for-each>
        </output>
    </xsl:template>
</xsl:stylesheet>

---

Command for generating the DLL:

"C:\Program Files (x86)\Microsoft SDKs\Windows\v10.0A\bin\NETFX 4.8 Tools\xsltc.exe" Stylesheet.xsl

Referencing the DLL in the SDK-style .csproj file:

<ItemGroup>
  <Reference Include="Stylesheet">
    <HintPath>.\Stylesheet.dll</HintPath>
  </Reference>
</ItemGroup>

input.xml:

<input>
  <book title="First Title" />
  <book title="Second Title" />
</input>

output.xml when executing the transformation with the non-compiled stylesheet:

<output>
  <booktitle>First Title</booktitle>
  <booktitle>Second Title</booktitle>
</output>

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I have researched and found other people having the same problem but haven't found a solution or an explanation on why the Microsoft Docs implicitly state it should work while it does not in my test.

• https://github.com/dotnet/runtime/issues/68129
• Using xsltc.exe generated assembly in .NET Core 2.2?
• XslCompiledTransform.Load(type) : Could not load file or assembly 'System.Data.SqlXml

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Stack trace of the System.IO.FileNotFoundException:

   at System.Delegate.BindToMethodInfo(Object target, IRuntimeMethodInfo method, RuntimeType methodType, DelegateBindingFlags flags)
   at System.Reflection.RuntimeMethodInfo.CreateDelegateInternal(Type delegateType, Object firstArgument, DelegateBindingFlags bindingFlags)
   at System.Reflection.RuntimeMethodInfo.CreateDelegate(Type delegateType)
   at System.Xml.Xsl.XslCompiledTransform.Load(MethodInfo executeMethod, Byte[] queryData, Type[] earlyBoundTypes)
   at System.Xml.Xsl.XslCompiledTransform.Load(Type compiledStylesheet)
   at TestXslDotnet6.Program.Main(String[] args) in C:\Users\UserNameRedacted\Path\To\Repo\TestXslDotnet6\TestXslDotnet6\Program.cs:line 10

Answer 1

Based on the information in the GitHub issue .NET 6 not support XslCompiledTransform.Load(type(myXsltCompiled_dll)), it looks as if this is not supported, and won't be.

A comment on April 18, 2022 said:

The assembly System.Data.SqlXml contains the namespace System.Xml.Xsl.Runtime, which is not present in .NET Core.

According to the porting guide, msxsl:script is unavailable on .NET Core. The .NET Framework specific tutorial is expected not to work.

A second person commented:

Looks like System.Data.SqlXml is part of SQLXML which is owned by the SQL Server org and as far as I know does not support .NET Core.

A third person replied:

There are currently no plans regarding SQLXML and support for .NET 5+, and we haven't heard many requests in this direction. I would recommend opening up a User Voice here to get some traction and consensus on the subject: https://aka.ms/sqlfeedback

So, that's your answer: "msxsl:script is unavailable on .NET Core. The .NET Framework specific tutorial is expected not to work." and the reason is that a non-.NET group would have to make it possible, but doesn't have plans to. They don't perceive a demand.

And, they acknowledge that the documentation is misleading. It appears that a change was made to the docs in May 2022, and a pull request created: Note that XSLT script blocks are .NET Framework only.

I recognize that this does not provide a solution or a way forward for you, and that is disappointing. But this is the answer to your question: doing a transform this way simply isn't supported in .NET 6.0.

Answer 2

Although it is about two years from this question I'd like to share workaround, that I've done for my purposes, because I didn't find any other solution, that helps using compiled XSLT dll in .NET Core based transformations.

So if you would like to use XslCompiledTransform class with dll types generated via xlstc.exe you follow these steps:

1. Generate dll class(es)

   xsltc.exe /class:Transform /out:Your.Assembly.dll

2. Disassembly your dll to ILL code

   ildasm Your.Assembly.dll /out=Your.Assembly.ill

3. Replace all occurences of [System.Data.SqlXml] with [System.Private.Xml] in Your.Assembly.ill

4. Compile you IL back to dll

   ilasm Your.Assembly.ill /dll

5. Now you can add Your.Assembly.dll reference to your .NET Core project