XML and XSLT transformation in ASP.NET MVC - XmlActionResult

In previous post I have written about HtmlHelper extensions for rendering XML in ASP.NET MVC. There are scenarios for which that approach is a little bit too much. For example, if all what we want to put in response is transformation result, we would have to make additional view to call our extension method. In such case it would be better to have dedicated ActionResult for XML transformation. So let's write one:

public class XmlActionResult: ActionResult
{
  ...
}

We will start by adding some necessary fields. Most of them will be also properties, but I will skip their code here (at the end you can find link to complete class).

public class XmlActionResult: ActionResult
{
  #region Fields
  private XmlDocument _xmlDocument;
  private XPathNavigator _xpathNavigator;
  private string _documentContent;
  private string _documentSource;
  private XslCompiledTransform _transform;
  private static XslCompiledTransform _transparentTransform;
  private string _transformSource;
  private XsltArgumentList _transformArgumentList;
  #endregion

  ...
}

Let's also add a static contructor with some initialization logic:

public class XmlActionResult: ActionResult
{
  ...

  #region Constructor
  static XmlActionResult()
  {
    XmlTextReader copyTransformReader = new XmlTextReader(new StringReader(
                                                          "<xsl:stylesheet version='1.0' xmlns:xsl='http://www.w3.org/1999/XSL/Transform'>
                                                          <xsl:template match=\"/\">
                                                          <xsl:copy-of select=\".\"/>
                                                          </xsl:template>
                                                          </xsl:stylesheet>"));
    _transparentTransform = new XslCompiledTransform();
    _transparentTransform.Load(copyTransformReader);
  }
  #endregion

  ...
}

Now it's time for heart of our ActionResult class- the ExecuteResult method:

public class XmlActionResult: ActionResult
{
  ...

  #region
  public override void ExecuteResult(ControllerContext context)
  {
    XPathDocument xpathDocument = null;
    //Checking if we have been given XmlDocument or XPathNavigator directly,
    if ((_xmlDocument == null) && (_xpathNavigator == null))
    {
      //Checking if we have document content
      if (!String.IsNullOrEmpty(_documentContent))
      {
        StringReader documentReader = new StringReader(_documentContent);
        xpathDocument = new XPathDocument(documentReader);
      }
      //Checking if we have path for document
      else if (!String.IsNullOrEmpty(_documentSource) && (_documentSource.Trim().Length != 0))
      {
        //Checking if path is absolute or relative
        if (!Path.IsPathRooted(_documentSource))
          //Mapping the relative path
          documentSource = context.HttpContext.Server.MapPath(_documentSource);

        //Loading XML from file into XPathDocument
        using (FileStream documentStream = new FileStream(_documentSource,
               FileMode.Open, FileAccess.Read, FileShare.Read))
        {
          XmlTextReader documentReader = new XmlTextReader(documentStream);
          xpathDocument = new XPathDocument(documentReader);
        }
      }
    }

    //Checking if we have been given XslCompiledTransform directly,
    //or do we have path for transform
    if ((_transform == null) &&
(!String.IsNullOrEmpty(_transformSource) && (_transformSource.Trim().Length != 0)))
    {
      //Checking if path is absolute or relative
      if (!Path.IsPathRooted(_transformSource))
        //Mapping the relative path
        _transformSource = context.HttpContext.Server.MapPath(_transformSource);

      //Loading XSLT from file into XslCompiledTransform
      using (FileStream transformStream = new FileStream(_transformSource,
             FileMode.Open, FileAccess.Read, FileShare.Read))
      {
        XmlTextReader tranformReader = new XmlTextReader(transformStream);
        _transform = new XslCompiledTransform();
        _transform.Load(tranformReader);
      }
    }

    //Checking if we have XML in any form
    if (((_xmlDocument != null) || (xpathDocument != null)) || (_xpathNavigator != null))
    {
      context.HttpContext.Response.ContentType = "text/html";

      //Checking if we have XSLT
      if (_transform == null)
        //If not, let's use transparent one
        _transform = _transparentTransform;

      //Perform transformation based on form in which we have our XML
      if (_xmlDocument != null)
        _transform.Transform((IXPathNavigable)_xmlDocument, _transformArgumentList,
                            context.HttpContext.Response.Output);
      else if (_xpathNavigator != null)
        _transform.Transform(_xpathNavigator, _transformArgumentList,
                            context.HttpContext.Response.Output);
      else
        _transform.Transform((IXPathNavigable)xpathDocument, _transformArgumentList,
                            context.HttpContext.Response.Output);
    }
  }
  #endregion
}

The XmlActionResult class is ready, so we can prepare a controller action which will use it:

public ActionResult XmlResult()
{
  XmlDocument cdCatalogDocument = new XmlDocument();
  cdCatalogDocument.Load(Server.MapPath("~/App_Data/CDCatalog.xml"));

  XmlActionResult result = new XmlActionResult();
  result.Document = cdCatalogDocument;
  result.TransformSource = Server.MapPath("~/Xslt/CDCatalog.xsl");
  return result;
}

This is the result of our hard work:

Complete class can be downloaded here. I hope someone will find it useful.