Question

I’m trying to validate an XML file against the schemas it references. (Using Delphi and MSXML2_TLB.) The (relevant part of the) code looks something like this:

procedure TfrmMain.ValidateXMLFile; var     xml: IXMLDOMDocument2;     err: IXMLDOMParseError;     schemas: IXMLDOMSchemaCollection; begin     xml := ComsDOMDocument.Create;     if xml.load('Data/file.xml') then     begin         schemas := xml.namespaces;         if schemas.length > 0 then         begin             xml.schemas := schemas;             err := xml.validate;         end;     end; end; 

This has the result that cache is loaded (schemas.length > 0), but then the next assignment raises an exception: ‘only XMLSchemaCache-schemacollections can be used.’

How should I go about this?

Answer 1

I’ve come up with an approach that seems to work. I first load the schema’s explicitly, then add themn to the schemacollection. Next I load the xml-file and assign the schemacollection to its schemas property. The solution now looks like this:

uses MSXML2_TLB   That is:   // Type Lib: C:\Windows\system32\msxml4.dll   // LIBID: {F5078F18-C551-11D3-89B9-0000F81FE221}  function TfrmMain.ValidXML(     const xmlFile: String;      out err: IXMLDOMParseError): Boolean; var     xml, xsd: IXMLDOMDocument2;     cache: IXMLDOMSchemaCollection; begin     xsd := CoDOMDocument40.Create;     xsd.Async := False;     xsd.load('http://the.uri.com/schemalocation/schema.xsd');      cache := CoXMLSchemaCache40.Create;     cache.add('http://the.uri.com/schemalocation', xsd);      xml := CoDOMDocument40.Create;     xml.async := False;     xml.schemas := cache;      Result := xml.load(xmlFile);     if not Result then       err := xml.parseError     else       err := nil; end; 

It is important to use XMLSchemaCache40 or later. Earlier versions don’t follow the W3C XML Schema standard, but only validate against XDR Schema, a MicroSoft specification.

The disadvantage of this solution is that I need to load the schema’s explicitly. It seems to me that it should be possible to retrieve them automatically.