在Web Services方法中，往往使用的都是一个具体类型的参数，这个参数一般就是一个数据对象。ASP.NET Web Services通过声明XmlIncludeAttribute可以实现Web Services方法中运用多态。
XmlIncludeAttribute允许XmlSerializer在序列化火反序列化对象时识别类型。当应用XmlIncludeAttribute时，需指定派生类的Type。XmlSerializer序列化同时包含基类和派生类的对象之后，它就可以识别两种对象类型。
首先定义基类Vehicle和派生类Car：
public
abstract
class
Vehicle
{
public string LicenseNumber{ get ; set ;}
public DateTime MakeTime { get ; set ; }
}
public class Car : Vehicle
{
public int DoorNum { get ; set ; }
}
{
public string LicenseNumber{ get ; set ;}
public DateTime MakeTime { get ; set ; }
}
public class Car : Vehicle
{
public int DoorNum { get ; set ; }
}
定义AddVehicle的Web Method，声明XmlInclude需要添加对命名空间System.Xml.Serialization的引用：
[WebMethod]
[XmlInclude( typeof (Car))]
public void AddVehicle(Vehicle vehicle)
{
}
[XmlInclude( typeof (Car))]
public void AddVehicle(Vehicle vehicle)
{
}
查看生成的wsdl，wsdl利用extension的base属性来描述Car继承Vechicle。
查看引用Web Services生成的Reference.cs文件，Vehicle类会有XmlIncludeAttribute的声明：
[System.Xml.Serialization.XmlIncludeAttribute(
typeof
(Car))]
[System.CodeDom.Compiler.GeneratedCodeAttribute( " System.Xml " , " 4.0.30319.1 " )]
[System.SerializableAttribute()]
[System.Diagnostics.DebuggerStepThroughAttribute()]
[System.ComponentModel.DesignerCategoryAttribute( " code " )]
[System.Xml.Serialization.XmlTypeAttribute(Namespace = " http://tempuri.org/ " )]
public abstract partial class Vehicle : object
[System.CodeDom.Compiler.GeneratedCodeAttribute( " System.Xml " , " 4.0.30319.1 " )]
[System.SerializableAttribute()]
[System.Diagnostics.DebuggerStepThroughAttribute()]
[System.ComponentModel.DesignerCategoryAttribute( " code " )]
[System.Xml.Serialization.XmlTypeAttribute(Namespace = " http://tempuri.org/ " )]
public abstract partial class Vehicle : object
客户端测试代码：
static
void
Main(
string
[] args)
{
localhost.WebService1SoapClient c = new localhost.WebService1SoapClient();
localhost.Car car = new localhost.Car() {
LicenseNumber = " 0001 " ,
MakeTime = DateTime.Now,
DoorNum = 2
};
c.AddVehicle(car);
}
{
localhost.WebService1SoapClient c = new localhost.WebService1SoapClient();
localhost.Car car = new localhost.Car() {
LicenseNumber = " 0001 " ,
MakeTime = DateTime.Now,
DoorNum = 2
};
c.AddVehicle(car);
}
在Web Services的AddVehicle方法可以查看传过来的参数：
Web Services可以支持多态，不过仅仅限制在可以直接引用Web Services的时候有生成可序列化的代码时能够使用，要在其他的客户端使用还是得费一番周折。
