<%@ WebService Language="vb" Class="Test" %>

Imports System.Web.Services
Imports System.Web.Services.Protocols
Imports System.Web.Services.Description
Imports System.Xml
Imports System.Xml.Schema
Imports System.Xml.Serialization
Imports System.Data

Public Class Test
    Inherits WebService
    <WebMethod()>
    Public Function EchoString(<XmlElement(DataType:="string")> ByVal strval As String) As <XmlElement("MyTime", DataType:="time")> Date
        Return Date.Now
    End Function

    <WebMethod(), XmlInclude(GetType(Car)), XmlInclude(GetType(Bike))>
    Public Function Vehicle(ByVal licenseNumber As String) As Vehicle
        If licenseNumber = "0" Then
            Dim v As Vehicle = New Car()
            v.licenseNumber = licenseNumber
            Return v
        ElseIf licenseNumber = "1" Then
            Dim v As Vehicle = New Bike()
            v.licenseNumber = licenseNumber
            Return v
        Else
            Return Nothing
        End If
    End Function
End Class
<XmlRoot("NewVehicle")>
Public MustInherit Class Vehicle
    Public licenseNumber As String
    Public make As Date
End Class

Public Class Car
    Inherits Vehicle
End Class

Public Class Bike
    Inherits Vehicle
End Class

<%@ WebService Language="C#" Class="Test" %>

using System;
using System.Web.Services;
using System.Web.Services.Protocols;
using System.Web.Services.Description;
using System.Xml;
using System.Xml.Schema;
using System.Xml.Serialization;
using System.Data;

public class Test : WebService {
   [WebMethod()]
   [return:XmlElement("MyTime", DataType="time")]
   public DateTime EchoString([XmlElement(DataType="string")] 
   string strval) {
        return DateTime.Now;
   }

   [WebMethod()]
   [XmlInclude(typeof(Car)), XmlInclude(typeof(Bike))]
   public Vehicle Vehicle(string licenseNumber) {
      if (licenseNumber == "0") {
         Vehicle v = new Car();
         v.licenseNumber = licenseNumber;
         return v;
      }
      else if (licenseNumber == "1") {
          Vehicle v = new Bike();
          v.licenseNumber = licenseNumber;
          return v;
      }
      else {
         return null;
      }
   }
}
[XmlRoot("NewVehicle")] 
public abstract class Vehicle {
    public string licenseNumber;
    public DateTime make;
}

public class Car : Vehicle {
}

public class Bike : Vehicle {
}