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How to validate using XSD (LINQ to XML)

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The System.Xml.Schema namespace contains extension methods that make it easy to validate an XML tree against an XML Schema Definition Language (XSD) file. For more information, see the Validate method documentation.

Example: Validate XDocument objects against an XmlSchemaSet

The following example creates an XmlSchemaSet, then validates two XDocument objects against the schema set. One of the documents is valid, the other isn't.

string xsdMarkup =
    @"<xsd:schema xmlns:xsd='http://www.w3.org/2001/XMLSchema'>
       <xsd:element name='Root'>
        <xsd:complexType>
         <xsd:sequence>
          <xsd:element name='Child1' minOccurs='1' maxOccurs='1'/>
          <xsd:element name='Child2' minOccurs='1' maxOccurs='1'/>
         </xsd:sequence>
        </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 XElement("Child1", "content1"),
        new XElement("Child2", "content1")
    )
);

XDocument doc2 = new XDocument(
    new XElement("Root",
        new XElement("Child1", "content1"),
        new XElement("Child3", "content1")
    )
);

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

Console.WriteLine();
Console.WriteLine("Validating doc2");
errors = false;
doc2.Validate(schemas, (o, e) =>
                     {
                         Console.WriteLine("{0}", e.Message);
                         errors = true;
                     });
Console.WriteLine("doc2 {0}", errors ? "did not validate" : "validated");

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 XElement = _
        <xsd:schema xmlns:xsd='http://www.w3.org/2001/XMLSchema'>
            <xsd:element name='Root'>
                <xsd:complexType>
                    <xsd:sequence>
                        <xsd:element name='Child1' minOccurs='1' maxOccurs='1'/>
                        <xsd:element name='Child2' minOccurs='1' maxOccurs='1'/>
                    </xsd:sequence>
                </xsd:complexType>
            </xsd:element>
        </xsd:schema>
    Dim schemas As XmlSchemaSet = New XmlSchemaSet()
    schemas.Add("", xsdMarkup.CreateReader)

    Dim doc1 As XDocument = _
        <?xml version='1.0'?>
        <Root>
            <Child1>content1</Child1>
            <Child2>content1</Child2>
        </Root>

    Dim doc2 As XDocument = _
        <?xml version='1.0'?>
        <Root>
            <Child1>content1</Child1>
            <Child3>content1</Child3>
        </Root>

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

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

Example: Validate an XML document from a file against a schema from a file

The following example validates that the XML document from Sample XML file: Customers and orders is valid per the schema from Sample XSD file: Customers and orders. It then modifies the source XML document. It changes the CustomerID attribute on the first customer. After the change, orders will then refer to a customer that doesn't exist, so the XML document will no longer validate.

XmlSchemaSet schemas = new XmlSchemaSet();
schemas.Add("", "CustomersOrders.xsd");

Console.WriteLine("Attempting to validate");
XDocument custOrdDoc = XDocument.Load("CustomersOrders.xml");
bool errors = false;
custOrdDoc.Validate(schemas, (o, e) =>
                     {
                         Console.WriteLine("{0}", e.Message);
                         errors = true;
                     });
Console.WriteLine("custOrdDoc {0}", errors ? "did not validate" : "validated");

Console.WriteLine();
// Modify the source document so that it won't validate.
custOrdDoc.Root.Element("Orders").Element("Order").Element("CustomerID").Value = "AAAAA";
Console.WriteLine("Attempting to validate after modification");
errors = false;
custOrdDoc.Validate(schemas, (o, e) =>
                     {
                         Console.WriteLine("{0}", e.Message);
                         errors = true;
                     });
Console.WriteLine("custOrdDoc {0}", errors ? "did not validate" : "validated");

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 schemas As XmlSchemaSet = New XmlSchemaSet()
    schemas.Add("", "CustomersOrders.xsd")

    Console.WriteLine("Attempting to validate")
    Dim custOrdDoc As XDocument = XDocument.Load("CustomersOrders.xml")
    errors = False
    custOrdDoc.Validate(schemas, AddressOf XSDErrors)
    Console.WriteLine("custOrdDoc {0}", IIf(errors, "did not validate", "validated"))

    Console.WriteLine()
    ' Modify the source document so that it won't validate.
    custOrdDoc.<Root>.<Orders>.<Order>.<CustomerID>(0).Value = "AAAAA"
    Console.WriteLine("Attempting to validate after modification")
    errors = False
    custOrdDoc.Validate(schemas, AddressOf XSDErrors)
    Console.WriteLine("custOrdDoc {0}", IIf(errors, "did not validate", "validated"))
End Sub

This example produces the following output:

Attempting to validate
custOrdDoc validated

Attempting to validate after modification
The key sequence 'AAAAA' in Keyref fails to refer to some key.
custOrdDoc did not validate

See also