Possible to add a XSLT Stylesheet to a serialized XML document?

Question

I have code that serializes a complex object to XML and saves it as a file, is there a quick way to include a style sheet in the xml during the serialization?

Using C# and .net framework v2.

Answer 1

You can use an XmlWriter and WriteProcessingInstruction :

    XmlSerializer s = new XmlSerializer(typeof(myObj));
    using (XmlWriter w = XmlWriter.Create(@"c:\test.xml"))
    {
        w.WriteProcessingInstruction("xml-stylesheet", "type=\"text/xsl\" href=\"USED-FILE.xsl\"");
        s.Serialize(w, myObj);
    }

Answer 2

For those who are wondering how to achieve similar things in modern dotnet core you gonna need to make few adjustments:

using System.Collections.Generic;
using System.Threading.Tasks;
using System.Xml;
using System.Xml.Serialization;
using Microsoft.AspNetCore;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Formatters;
using Microsoft.Extensions.DependencyInjection;

namespace ContentNegotiation
{
    public class Program
    {
        public static void Main(string[] args) => CreateWebHostBuilder(args).Build().Run();

        public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
            WebHost.CreateDefaultBuilder(args)
                .UseStartup<Startup>();
    }

    public class MyXmlSerializerOutputFormatter : XmlSerializerOutputFormatter
    {
        protected override void Serialize(XmlSerializer xmlSerializer, XmlWriter xmlWriter, object value)
        {
            // TODO: add me only if controller has some kind of custom attribute with XSLT file name
            xmlWriter.WriteProcessingInstruction("xml-stylesheet", "type=\"text/xsl\" href=\"template.xsl\"");
            base.Serialize(xmlSerializer, xmlWriter, value);
        }
    }

    public class Startup
    {
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddMvc(options =>
            {
                options.RespectBrowserAcceptHeader = true; // default is false
                // options.OutputFormatters.Add(new XmlSerializerOutputFormatter()); // not enough
                options.OutputFormatters.Add(new MyXmlSerializerOutputFormatter());
            })
            // .AddXmlSerializerFormatters() // does not added by default, but not enough
            .SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
        }

        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            app.UseStaticFiles();
            app.UseMvc();
        }
    }

    public class Post
    {
        public int Id { get; set; }
        public string Title { get; set; }
        public string Body { get; set; }
    }

    [ApiController]
    public class DemoController : ControllerBase
    {
        // curl -k -i -s -H 'Accept: text/xml' http://localhost:5000/posts
        // curl -k -i -s -H 'Accept: application/json' http://localhost:5000/posts
        [HttpGet]
        [Route(nameof(Posts))]
        public IEnumerable<Post> Posts() => new[] {
            new Post {
                Id = 1,
                Title = "Hello World",
                Body = "Lorem ipsum dot color"
            },
            new Post {
                Id = 2,
                Title = "Post 2",
                Body = "Lorem ipsum dot color"
            }
        };
    }
}

We are turning on content negotiation in ConfigureServices and giving our implementation of XmlSerializerOutputFormatter which will add XSL to the output

So now our backend will respond with JSON to requests like:

curl -k -i -s -H 'Accept: application/json' http://localhost:5000/posts

and XML:

curl -k -i -s -H 'Accept: text/xml' http://localhost:5000/posts

Sample of xsl for demo purposes might be found here: https://mac-blog.org.ua/dotnet-content-negotiation/