Question

In the Java XML transformation package, there is a concept known as a URIResolver, which is “An object that implements this interface that can be called by the processor to turn a URI used in document(), xsl:import, or xsl:include into a Source object.”

So, if your XSL has an import like this

<xsl:import href="URI"/> 

This allows you to take URI and map it to the Source of your choice – maybe it comes from a database, or maybe you want to map the URI to another URI. This can be useful, since you can’t use an xsl:variable in the xsl:import href.

Here is some sample Java code that creates a transformer and does a transform.

URIResolver uriResolver = new MyURIResolver();  // sample
TransformerFactory transformerFactory = TransformerFactory.newInstance();
transformerFactory.setURIResolver(uriResolver);
Transformer transformer = transformerFactory.newTransformer();
transformer.setURIResolver(uriResolver);
transformer.transform(xml, result);

Note, there are two places in the code where the URIResolver is used:

• TransformerFactory
  setURIResolver – “Set an object
  that is used by default during the
  transformation to resolve URIs used
  in document(), xsl:import, or
  xsl:include.”
• Transformer setURIResolver – “Set
  an object that will be used to
  resolve URIs used in document().”

Question: Is there a similar concept to the Java URIResolver in C# and .NET?

Answer 1

Yes, it’s called XmlResolver.

XmlResolver is one of System.Xml abstractions, which means you can use it in various APIs, such as XslCompiledTransform, XmlDocument, XmlReader (via XmlReaderSettings), etc.

Here’s a more in-depth on how it works, and how you can implement your own resolver.

By default, these various APIs use the XmlUrlResolver, which can resolve URIs that start with http:// and file://.

In addition, for resolving external entities, you can override the default ResolveEntity method on XmlReader.