Saxon

Formatting error, this should have been in the code block: Processor processor = new Processor();

I think the most likely reason is that your stylesheet contains a global variable that is dependent (directly or indirectly) on the global context item, and you have not set a global context item.

In XSLT 3.0 the "global context item" and the "initial match selection" can be set independently, and the applyTemplates() invocation method only sets the initial match selection. From the command line (for reasons of tradition) the -s option sets both, and you can also set both using the XsltTransformer.transform() method. Alternatively, you can set the global context item directly on the XsltTransformer.

@Michael, so the error is present in the samples as https://dev.saxonica.com/repos/archive/opensource/latest9.9/samples/styles/books.xsl has the global variable <xsl:variable name="categories" select="//CATEGORY"/> and https://dev.saxonica.com/repos/archive/opensource/latest9.9/samples/cs/ExamplesHE.cs in the example XsltSimple1 does not use the transform method (I don't think it exists on the .NET side of the API so far) nor does it set the global context item:

    public class XsltSimple1 : Example
    {

        public override String testName
        {
            get { return "XsltSimple1"; }
        }

        public override void run(Uri samplesDir)
        {
            // Create a Processor instance.
            Processor processor = new Processor();

            // Load the source document
            XdmNode input = processor.NewDocumentBuilder().Build(new Uri(samplesDir, "data/books.xml"));

            // Create a transformer for the stylesheet.
            Xslt30Transformer transformer = processor.NewXsltCompiler().Compile(new Uri(samplesDir, "styles/books.xsl")).Load30();

            // Create a serializer, with output to the standard output stream
            Serializer serializer = processor.NewSerializer();
            serializer.SetOutputWriter(Console.Out);

            // Transform the source XML and serialize the result document
            transformer.ApplyTemplates(input, serializer);
        }
    }

I got this to run by doing the following changes:

  public override void run(Uri samplesDir)
    {
        // Create a Processor instance.

        Processor processor = new Processor();

        // Load the source document
        XdmNode input = processor.NewDocumentBuilder().Build(new Uri(samplesDir, "data/books.xml"));

        // Create a transformer for the stylesheet.
        // Xslt30Transformer transformer = processor.NewXsltCompiler().Compile(new Uri(samplesDir, "styles/books.xsl")).Load30();
        XsltTransformer transformer = processor.NewXsltCompiler().Compile(new Uri(samplesDir, "styles/books.xsl")).Load();

        // Set the root node of the source document to be the initial context node
        transformer.InitialContextNode = input;

        // Create a serializer, with output to the standard output stream
        Serializer serializer = processor.NewSerializer();
        serializer.SetOutputWriter(Console.Out);

        // Transform the source XML and serialize the result document
        // transformer.ApplyTemplates(input, serializer);     // XPDY0002 exception here 
        transformer.Run(serializer);     // transformer.transform() does not seem to exist in the .NET version
    }

I was using the data and styles files unmodified from the samples. There seems to be a mismatch between the sample files and the sample source code. Still this was a learning experience for me. I don't need the XSLT 3 version features.

Thanks for the update. Anyway the quick response is a sign of a product that is actively supported.