Extensions.Validate Method (XAttribute, XmlSchemaObject, XmlSchemaSet, ValidationEventHandler)

 
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This method validates that an XAttribute conforms to a specified XmlSchemaObject and an XmlSchemaSet.

Namespace:   System.Xml.Schema
Assembly:  System.Xml.Linq (in System.Xml.Linq.dll)

public static void Validate(
	this XAttribute source,
	XmlSchemaObject partialValidationType,
	XmlSchemaSet schemas,
	ValidationEventHandler validationEventHandler
)

Parameters

source
Type: System.Xml.Linq.XAttribute

The XAttribute to validate.

partialValidationType
Type: System.Xml.Schema.XmlSchemaObject

An XmlSchemaObject that specifies the sub-tree to validate.

schemas
Type: System.Xml.Schema.XmlSchemaSet

An XmlSchemaSet to validate against.

validationEventHandler
Type: System.Xml.Schema.ValidationEventHandler

A ValidationEventHandler for an event that occurs when the reader encounters validation errors. If null, throws an exception upon validation errors.

Exception Condition
XmlSchemaValidationException

Thrown for XML Schema Definition Language (XSD) validation errors.

You can use this method to validate that an XAttribute conforms to a schema. You typically use this method when you have modified an attribute, and you want to make sure that it still conforms to its schema. You could validate the entire document, but it takes less processing time to validate just the attribute.

If you pass null for validationEventHandler, this method raises an exception upon validation errors. Validation warnings will not raise an exception.

To validate an attribute, you use an instance of XmlSchemaObject. You can obtain this instance in various ways. An easy way is as follows:

  1. Validate that a document conforms to a schema.

  2. Add the post-schema-validation infoset (PSVI) by calling the Validate extension method.

  3. Call the GetSchemaInfo extension method to retrieve an object that implements IXmlSchemaInfo. From the retrieved object, you can get an XmlSchemaObject.

After you have an instance of an XmlSchemaObject, you can use this method to validate an attribute.


                string xsdMarkup =
    @"<xsd:schema xmlns:xsd='http://www.w3.org/2001/XMLSchema'>
       <xsd:element name='Root'>
        <xsd:complexType>
         <xsd:simpleContent>
          <xsd:extension base='xsd:string'>
           <xsd:attribute name='Lang' use='required'>
            <xsd:simpleType>
             <xsd:restriction base='xsd:token'>
              <xsd:enumeration value='C#'/>
              <xsd:enumeration value='VB'/>
             </xsd:restriction>
            </xsd:simpleType>
           </xsd:attribute>
          </xsd:extension>
         </xsd:simpleContent>
        </xsd:complexType>
       </xsd:element>
      </xsd:schema>";

XmlSchemaSet schemas = new XmlSchemaSet();
schemas.Add("", XmlReader.Create(new StringReader(xsdMarkup)));

XDocument doc1 = new XDocument(
    new XElement("Root",
        new XAttribute("Lang", "C#")
    )
);

Console.WriteLine("Validating doc1 ...");
bool errors = false;
doc1.Validate(schemas, (sender, e) =>
    {
        Console.WriteLine(e.Message);
        errors = true;
    }, true);
Console.WriteLine("doc1 {0}", errors ? "did not validate" : "validated");

Console.WriteLine();
Console.WriteLine("Validating Lang attribute ...");
XAttribute lang = doc1.Root.Attribute("Lang");

errors = false;
lang.Validate(lang.GetSchemaInfo().SchemaAttribute, schemas, (sender, e) =>
    {
        Console.WriteLine(e.Message);
        errors = true;
    });
Console.WriteLine("lang {0}", errors ? "did not validate" : "validated");

// the following makes the Lang attribute invalid according to the schema
lang.Value = "VC";

Console.WriteLine();
Console.WriteLine("Validating Lang attribute ...");

errors = false;
lang.Validate(lang.GetSchemaInfo().SchemaAttribute, schemas, (sender, e) =>
    {
        Console.WriteLine(e.Message);
        errors = true;
    });
Console.WriteLine("lang {0}", errors ? "did not validate" : "validated");

This example produces the following output:

Validating doc1 ...
doc1 validated

Validating Lang attribute ...
lang validated

Validating Lang attribute ...
The 'Lang' attribute is invalid - The value 'VC' is invalid according to its datatype 'Token' - The Enumeration constraint failed.
lang did not validate

.NET Framework
Available since 3.5
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