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Posted 13 Oct 2008
Licenced CPOL

Parsing XSD Schema with SOM

, 13 Oct 2008
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Pull metadata from a schema or generate XML mappers


This article shows how to use a Schema Object Model(SOM) navigator as an arbitrary schema. This is useful when you have a schema and want to generate your own mapping or want to build a custom XML generator or XSD based code generator.

Using the Code

First read schema and "compile", this will validate the schema.

private static XmlSchema
ReadAndCompileSchema(string fileName)
    XmlTextReader tr = new XmlTextReader(fileName,
                        new NameTable());

    // The Read method will throw errors encountered
    // on parsing the schema
    XmlSchema schema = XmlSchema.Read(tr,
           new ValidationEventHandler(ValidationCallbackOne));

    XmlSchemaSet xset = new XmlSchemaSet();

    xset.ValidationEventHandler += new ValidationEventHandler(ValidationCallbackOne);

    // The Compile method will throw errors
    // encountered on compiling the schema

    return schema;

private static void ValidationCallbackOne(object sender, ValidationEventArgs args)
    Console.WriteLine("Exception Severity: " + args.Severity);

Start traversing at the highest level...

private static void TraverseSOM(string xsfFilename)
    XmlSchema custSchema = ReadAndCompileSchema(xsfFilename);

    foreach (XmlSchemaElement elem in

Only an element can contain attributes... so it's handled in a little special way:

private static void ProcessElement(XmlSchemaElement elem)
    Console.WriteLine("Element: {0}", elem.Name);

    if (elem.ElementSchemaType is XmlSchemaComplexType)
	XmlSchemaComplexType ct = 
		elem.ElementSchemaType as XmlSchemaComplexType;

	foreach (DictionaryEntry obj in ct.AttributeUses)
		Console.WriteLine("Attribute: {0}  ", 
		(obj.Value as XmlSchemaAttribute).Name);


Process the Choice & Sequence elements generically (this handles the type casting required):

private static void ProcessSequence(XmlSchemaSequence sequence)

private static void ProcessChoice(XmlSchemaChoice choice)

The Schema objects are processed generically, but uniformly:

private static void ProcessItemCollection(XmlSchemaObjectCollection objs)
    foreach (XmlSchemaObject obj in objs)

private static void ProcessSchemaObject(XmlSchemaObject obj)
    if (obj is XmlSchemaElement)
        ProcessElement(obj as XmlSchemaElement);
    if (obj is XmlSchemaChoice)
        ProcessChoice(obj as XmlSchemaChoice);
    if (obj is XmlSchemaSequence)
        ProcessSequence(obj as XmlSchemaSequence);

Points of Interest

There's a lot of type checking and casting. That's inherent in the data model used in the SOM. It's not a strongly typed data structure. So you have to check, cast, then use. It would be an interesting exercise to generate a strongly typed XSD model, but I'll leave that for another article.


  • 2008-10-10: Article created


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Engineer Big Company
United States United States
My professional career began as a developer fixing bugs on Microsoft Word97 and I've been fixing bad habits ever since. Now I do R&D work writing v1 line of business applications mostly in C#/.Net.

I've been an avid pilot/instructor for 13+ years, I've built two airplanes and mostly fly gliders now for fun. I commute in an all-electric 1986 BMW 325 conversion.

I'd like to get back to my academic roots of programming 3D analysis applications to organize complex systems.

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Comments and Discussions

QuestionThanks a lot! Pin
DanielLey18-Mar-12 12:50
memberDanielLey18-Mar-12 12:50 

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