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description title ms.date dev_langs ms.assetid
Learn more about: Traversing XML Schemas
Traversing XML Schemas
03/30/2017
csharp
vb
cpp
cce69574-5861-4a30-b730-2e18d915d8ee

Traversing XML Schemas

Traversing an XML schema using the Schema Object Model (SOM) API provides access to the elements, attributes, and types stored in the SOM. Traversing an XML schema loaded into the SOM is also the first step in editing an XML schema using the SOM API.

Traversing an XML Schema

The following properties of the xref:System.Xml.Schema.XmlSchema class provide access to the collection of all global items added to the XML schema.

Property Object type stored in the collection or array
xref:System.Xml.Schema.XmlSchema.Elements%2A xref:System.Xml.Schema.XmlSchemaElement
xref:System.Xml.Schema.XmlSchema.Attributes%2A xref:System.Xml.Schema.XmlSchemaAttribute
xref:System.Xml.Schema.XmlSchema.AttributeGroups%2A xref:System.Xml.Schema.XmlSchemaAttributeGroup
xref:System.Xml.Schema.XmlSchema.Groups%2A xref:System.Xml.Schema.XmlSchemaGroup
xref:System.Xml.Schema.XmlSchema.Includes%2A xref:System.Xml.Schema.XmlSchemaExternal, xref:System.Xml.Schema.XmlSchemaInclude, xref:System.Xml.Schema.XmlSchemaImport, or xref:System.Xml.Schema.XmlSchemaRedefine
xref:System.Xml.Schema.XmlSchema.Items%2A xref:System.Xml.Schema.XmlSchemaObject (provides access to all global level elements, attributes, and types).
xref:System.Xml.Schema.XmlSchema.Notations%2A xref:System.Xml.Schema.XmlSchemaNotation
xref:System.Xml.Schema.XmlSchema.SchemaTypes%2A xref:System.Xml.Schema.XmlSchemaType, xref:System.Xml.Schema.XmlSchemaSimpleType, xref:System.Xml.Schema.XmlSchemaComplexType
xref:System.Xml.Schema.XmlSchema.UnhandledAttributes%2A xref:System.Xml.XmlAttribute (provides access to attributes that do not belong to the schema namespace)

Note

All of the properties listed in the table above, except for the xref:System.Xml.Schema.XmlSchema.Items%2A property, are Post-Schema-Compilation-Infoset (PSCI) properties that are not available until the schema has been compiled. The xref:System.Xml.Schema.XmlSchema.Items%2A property is a pre-schema-compilation property that can be used before the schema has been compiled to access and edit all global level elements, attributes, and types.

The xref:System.Xml.Schema.XmlSchema.UnhandledAttributes%2A property provides access to all the attributes that do not belong to the schema namespace. These attributes are not processed by the schema processor.

The code example that follows demonstrates traversing the customer schema created in the Building XML Schemas topic. The code example demonstrates traversing the schema using the collections described above and writes all the elements and attributes in the schema to the console.

The sample traverses the customer schema in the following steps.

  1. Adds the customer schema to a new xref:System.Xml.Schema.XmlSchemaSet object and then compiles it. Any schema validation warnings and errors encountered reading or compiling the schema are handled by the xref:System.Xml.Schema.ValidationEventHandler delegate.

  2. Retrieves the compiled xref:System.Xml.Schema.XmlSchema object from the xref:System.Xml.Schema.XmlSchemaSet by iterating over the xref:System.Xml.Schema.XmlSchemaSet.Schemas%2A property. Because the schema is compiled, Post-Schema-Compilation-Infoset (PSCI) properties are accessible.

  3. Iterates over each xref:System.Xml.Schema.XmlSchemaElement in the xref:System.Xml.Schema.XmlSchemaObjectTable.Values%2A collection of the post-schema-compilation xref:System.Xml.Schema.XmlSchema.Elements%2A?displayProperty=nameWithType collection writing the name of each element to the console.

  4. Gets the complex type of the Customer element using the xref:System.Xml.Schema.XmlSchemaComplexType class.

  5. If the complex type has any attributes, gets an xref:System.Collections.IDictionaryEnumerator to enumerate over each xref:System.Xml.Schema.XmlSchemaAttribute and writes its name to the console.

  6. Gets the sequence particle of the complex type using the xref:System.Xml.Schema.XmlSchemaSequence class.

  7. Iterates over each xref:System.Xml.Schema.XmlSchemaElement in the xref:System.Xml.Schema.XmlSchemaSequence.Items%2A?displayProperty=nameWithType collection writing the name of each child element to the console.

The following is the complete code example.

[!code-cppXmlSchemaTraverseExample#1] [!code-csharpXmlSchemaTraverseExample#1] [!code-vbXmlSchemaTraverseExample#1]

The xref:System.Xml.Schema.XmlSchemaElement.ElementSchemaType%2A?displayProperty=nameWithType property can be xref:System.Xml.Schema.XmlSchemaSimpleType, or xref:System.Xml.Schema.XmlSchemaComplexType if it is a user-defined simple type or a complex type. It can also be xref:System.Xml.Schema.XmlSchemaDatatype if it is one of the built-in datatypes defined in the W3C XML Schema Recommendation. In the customer schema, the xref:System.Xml.Schema.XmlSchemaElement.ElementSchemaType%2A of the Customer element is xref:System.Xml.Schema.XmlSchemaComplexType, and the FirstName and LastName elements are xref:System.Xml.Schema.XmlSchemaSimpleType.

The code example in the Building XML Schemas topic used the xref:System.Xml.Schema.XmlSchemaComplexType.Attributes%2A?displayProperty=nameWithType collection to add the attribute CustomerId to the Customer element. This is a pre-schema-compilation property. The corresponding Post-Schema-Compilation-Infoset property is the xref:System.Xml.Schema.XmlSchemaComplexType.AttributeUses%2A?displayProperty=nameWithType collection, which holds all the attributes of the complex type, including the ones that are inherited through type derivation.

See also