Btukfyl

I'm trying to create an XmlSchemaSet against the SAML 2.0 set of schema definitions, starting with the protocol schema here: https://docs.oasis-open.org/security/saml/v2.0/saml-schema-protocol-2.0.xsd

var set = new XmlSchemaSet();



XmlSchema schema;

using (var reader = XmlReader.Create(

    "https://docs.oasis-open.org/security/saml/v2.0/saml-schema-protocol-2.0.xsd"))

{

    schema = XmlSchema.Read(reader, (sender, e) => Console.WriteLine(e.Message));

}



set.Add(schema);



set.Compile();

When Compile is called, the following exception is thrown:

System.Xml.Schema.XmlSchemaException

Type 'urn:oasis:names:tc:SAML:2.0:assertion:EncryptedElementType' is not declared.

   at System.Xml.Schema.XmlSchemaSet.InternalValidationCallback(Object sender, ValidationEventArgs e)

   at System.Xml.Schema.BaseProcessor.SendValidationEvent(XmlSchemaException e, XmlSeverityType severity)

   at System.Xml.Schema.BaseProcessor.SendValidationEvent(XmlSchemaException e)

   at System.Xml.Schema.Compiler.CompileElement(XmlSchemaElement xe)

   at System.Xml.Schema.Compiler.Compile()

   at System.Xml.Schema.Compiler.Execute(XmlSchemaSet schemaSet, SchemaInfo schemaCompiledInfo)

   at System.Xml.Schema.XmlSchemaSet.Compile()

   at XSD.Program.Main(String args)

The type specified urn:oasis:names:tc:SAML:2.0:assertion:EncryptedElementType appears in the namespace imported at the top of the schema:

<import

    namespace="urn:oasis:names:tc:SAML:2.0:assertion"

    schemaLocation="saml-schema-assertion-2.0.xsd"/>

Using Fiddler, I can't see the application making any attempts at retrieving the imported schema.

Why don't these import statements appear to be working with the XmlSchemaSet?

The default behaviour of the XmlSchemaSet is to not try to resolve any external schemas. To this this, the XmlResolver property must be set. The go-to resolver implementation is XmlUrlResolver:

set.XmlResolver = new XmlUrlResolver();

The important thing is to set this property before adding any schemas to the set. The call to Add performs "pre-processing" on the schema, which includes resolving any import statements. Assigning the XmlResolver after calling Add appears to have no effect.

The application code needs to be:

var set = new XmlSchemaSet

{

    // Enable resolving of external schemas.

    XmlResolver = new XmlUrlResolver()

};



XmlSchema schema;

using (var reader = XmlReader.Create(

    "https://docs.oasis-open.org/security/saml/v2.0/saml-schema-protocol-2.0.xsd"))

{

    schema = XmlSchema.Read(reader, (sender, e) => Console.WriteLine(e.Message));

}



set.Add(schema);



set.Compile();

NOTE The above code still does not actually produce the desired result due to problems loading the schemas from w3.org, however the imported SAML schema is resolved successfully.