Extensions.Validate Method (XElement, XmlSchemaObject, XmlSchemaSet, ValidationEventHandler, Boolean)

Validates that an XElement sub-tree conforms to a specified XmlSchemaObject and an XmlSchemaSet, optionally populating the XML tree with the post-schema-validation infoset (PSVI).

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

<ExtensionAttribute> _
Public Shared Sub Validate ( _
	source As XElement, _
	partialValidationType As XmlSchemaObject, _
	schemas As XmlSchemaSet, _
	validationEventHandler As ValidationEventHandler, _
	addSchemaInfo As Boolean _


Type: System.Xml.Linq.XElement

The XElement to validate.

Type: System.Xml.Schema.XmlSchemaObject

An XmlSchemaObject that specifies the sub-tree to validate.

Type: System.Xml.Schema.XmlSchemaSet

An XmlSchemaSet to validate against.

Type: System.Xml.Schema.ValidationEventHandler

A ValidationEventHandler for an event that occurs when the reader encounters validation errors. If Nothing, throws an exception upon validation errors.

Type: System.Boolean

A Boolean indicating whether to populate the post-schema-validation infoset (PSVI).

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type XElement. When you use instance method syntax to call this method, omit the first parameter. For more information, see Extension Methods (Visual Basic) or Extension Methods (C# Programming Guide).


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

You can use this method to validate that a sub-tree (with an XElement at the root of the sub-tree) conforms to a schema. You typically use this method when you have modified a sub-tree, 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 a just a sub-tree.

If addSchemaInfo is true, then this method populates the XML tree with the post-schema-validation infoset (PSVI).

There are two aspects of populating the XML tree with the PSVI.

First, an annotation is added to all nodes in the tree such that you can now call GetSchemaInfo on an element or attribute in the tree.

Second, default elements and attributes defined in the XSD are added to the XML tree. By calling one of the GetSchemaInfo methods, you can determine if a specific element or attribute was added from the XSD as a default element or attribute.

If you pass Nothing for validationEventHandler, then this method raises an exception upon validation errors. Validation warnings will not raise an exception.

To validate a sub-tree, 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 a sub-tree..

Dim errors As Boolean = False

Private Sub XSDErrors(ByVal o As Object, ByVal e As ValidationEventArgs)
    Console.WriteLine("{0}", e.Message)
    errors = True
End Sub

Sub Main()
    Dim xsdMarkup As XDocument = _
        <?xml version='1.0'?>
        <xsd:schema xmlns:xsd='http://www.w3.org/2001/XMLSchema'>
            <xsd:element name='Root'>
                        <xsd:element name='Child1' minOccurs='1' maxOccurs='1'/>
                        <xsd:element name='Child2' minOccurs='1' maxOccurs='1'>
                                    <xsd:extension base='xsd:string'>
                                        <xsd:attribute name='Att1' default='Att1 Default Value'/>
    Dim schemas As XmlSchemaSet = New XmlSchemaSet()
    schemas.Add("", xsdMarkup.CreateReader)

    Dim doc1 As XDocument = _
        <?xml version='1.0'?>

    Dim doc2 As XDocument = _
        <?xml version='1.0'?>

    Console.WriteLine("Validating doc1")
    errors = False
    doc1.Validate(schemas, AddressOf XSDErrors, True)
    Console.WriteLine("doc1 {0}", IIf(errors, "did not validate", "validated"))

    Console.WriteLine("Validating doc2")
    errors = False
    doc2.Validate(schemas, AddressOf XSDErrors, True)
    Console.WriteLine("doc2 {0}", IIf(errors, "did not validate", "validated"))

    Console.WriteLine("Contents of doc1:")

    Console.WriteLine("Contents of doc2:")
End Sub

This example produces the following output:

Validating doc1
doc1 validated

Validating doc2
The element 'Root' has invalid child element 'Child3'. List of possible elements expected: 'Child2'.
doc2 did not validate

Contents of doc1:
  <Child2 Att1="Att1 Default Value">c2</Child2>

Contents of doc2:

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5

.NET Framework Client Profile

Supported in: 4, 3.5 SP1
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