c# - Getting started with XSD validation with .NET

Question

Here is my first attempt at validating XML with XSD.

The XML file to be validated:

<?xml version="1.0" encoding="utf-8" ?>
<config xmlns="Schemas" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="config.xsd">
  <levelVariant>
    <filePath>SampleVariant</filePath>
  </levelVariant>
  <levelVariant>
    <filePath>LegendaryMode</filePath>
  </levelVariant>
  <levelVariant>
    <filePath>AmazingMode</filePath>
  </levelVariant>
</config>

The XSD, located in "Schemas/config.xsd" relative to the XML file to be validated:

<?xml version="1.0" encoding="utf-8" ?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified">
  <xs:element name="config">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="levelVariant">
          <xs:complexType>
            <xs:sequence>
              <xs:element name="filePath" type="xs:anyURI">
              </xs:element>
            </xs:sequence>
          </xs:complexType>
        </xs:element>
      </xs:sequence>
    </xs:complexType>
  </xs:element>
</xs:schema>

Right now, I just want to validate the XML file precisely as it appears currently. Once I understand this better, I'll expand more. Do I really need so many lines for something as simple as the XML file as it currently exists?

The validation code in C#:

        public void SetURI(string uri)
        {
            XElement toValidate = XElement.Load(Path.Combine(PATH_TO_DATA_DIR, uri) + ".xml");

// begin confusion

       // exception here
       string schemaURI = toValidate.Attributes("xmlns").First().ToString() 
                              + toValidate.Attributes("xsi:noNamespaceSchemaLocation").First().ToString();
        XmlSchemaSet schemas = new XmlSchemaSet();
        schemas.Add(null, schemaURI);

        XDocument toValidateDoc = new XDocument(toValidate);
        toValidateDoc.Validate(schemas, null);
// end confusion

            root = toValidate;
        }

Running the above code gives this exception:

The ':' character, hexadecimal value 0x3A, cannot be included in a name.

Any illumination would be appreciated.

Answer 1

Rather than using the XDocument.Validate extension method, I would use an XmlReader which can be configured to process an inline schema via XmlReaderSettings. You could do some thing like the following code.

public void VerifyXmlFile(string path)
{
    // configure the xmlreader validation to use inline schema.
    XmlReaderSettings config = new XmlReaderSettings();
    config.ValidationType = ValidationType.Schema;
    config.ValidationFlags |= XmlSchemaValidationFlags.ReportValidationWarnings;
    config.ValidationFlags |= XmlSchemaValidationFlags.ProcessInlineSchema;
    config.ValidationFlags |= XmlSchemaValidationFlags.ProcessSchemaLocation;
    config.ValidationEventHandler += new ValidationEventHandler(ValidationCallBack);

    // Get the XmlReader object with the configured settings.
    XmlReader reader = XmlReader.Create(path, config);

    // Parsing the file will cause the validation to occur.
    while (reader.Read()) ;

}

private void ValidationCallBack(object sender, ValidationEventArgs vea)
{
    if (vea.Severity == XmlSeverityType.Warning)
        Console.WriteLine(
            "Warning: Matching schema not found.  No validation occurred. {0}",
            vea.Message);
    else
        Console.WriteLine("Validation error: {0}", vea.Message);

}

The code above assumes the following using statements.

using System.Xml;
using System.Xml.Schema;

Just to keep this simple I did not return a boolean or a collection of validation errors, you could easily modify this to do so.

Note: I modified your config.xml and config.xsd to get them to validate. These are the changes I made.

config.xsd:

<xs:element maxOccurs="unbounded" name="levelVariant">

config.xml:

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="config.xsd">