Extracting Schemas for Nested Classes

In listing C.3 the two classes: garage and garageCar were listed sequentially, which does not reflect the relationship the types of the garageCar and garage element had in the schema in listing C.2 where the complexType of the car element was declared inline of the garage element. A nested class definition as shown in listing C.10 would be a closer match to the semantics of the schema.

10        Listing C.10 Nested definition of the Garage can garageCar classes

public class Garage

{

  public Garage()      { }

  public class garageCar

  {

    public garageCar(){}

    [System.Xml.Serialization.XmlAttributeAttribute()]

    public string make;

    [System.Xml.Serialization.XmlAttributeAttribute()]

    public string model;

    [System.Xml.Serialization.XmlAttributeAttribute()]

    public string year;

  }

  public string desc;

  [System.Xml.Serialization.XmlElementAttribute("car")]

  public Car[] car;

}

If we built an assembly class definition above and extracted a schema from that assembly, we would get a schema with the same validation semantics as the schema in listing C.2, i.e. without a top-level element for the garageCar class.

11        Listing C.11 Schema extracted from an assembly with nested classes

<?xml version="1.0" encoding="utf-8"?>

<xs:schema elementFormDefault="qualified"

  xmlns:xs="http://www.w3.org/2001/XMLSchema">

  <xs:element name="Garage" nillable="true" type="Garage" /> | #1

  <xs:complexType name="Garage">

    <xs:sequence>

      <xs:element minOccurs="0"

        maxOccurs="1" name="desc" type="xs:string" />

      <xs:element minOccurs="0"

        maxOccurs="unbounded" name="car" type="garageCar" />

    </xs:sequence>

  </xs:complexType>

  <xs:complexType name="garageCar">

    <xs:attribute name="make" type="xs:string" />

    <xs:attribute name="model" type="xs:string" />

    <xs:attribute name="year" type="xs:string" />

  </xs:complexType>

</xs:schema>

(annotation) <#1  Nested classes only produce an element for the outer class. >

Extracting Types using XmlTypeAttribute

When the XSD tool analyzes an assembly to generate a schema, it inspects every class for the XmlTypeAttribute. By default each class in the assembly produces a complexType in the schema. The XmlTypeAttribute’s TypeName can specify an alternate name for complexType. If the IncludeInSchema property is set to false the tool will exclude the class from the schema.

Extracting Specific Classes from an Assembly

If we need to generate a schema only for certain classes in an assembly, we can supply a /t command-line option for each class we want to include in the schema. If we only need an element for the garageCar class in the garage.dll assembly from section C.5.1 we would invoke xsd.exe as follows:

xsd.exe garage.dll /t:garageCar

Now the output schema only contains a garageCar element and its type description:

<?xml version="1.0" encoding="utf-8" ?>

<xs:schema elementFormDefault="qualified"

  xmlns:xs="http://www.w3.org/2001/XMLSchema">

  <xs:element name="garageCar" nillable="true" type="garageCar" />

  <xs:complexType name="garageCar">

    <xs:attribute name="make" type="xs:string" />

    <xs:attribute name="model" type="xs:string" />

    <xs:attribute name="year" type="xs:string" />

  </xs:complexType>

</xs:schema>

The parameter to the /t switch is treated like a pattern to match class names inside the assembly. If we do not explicitly qualify the class name with a .NET namespace, the tool will include all classes matching the supplied name. We can even provide wildcards with the asterisk character (*), for example /t:garage* would produce a schema with for the classes garage and garageCar.