public abstract class Vehicle 
 { 
   public string LicenseNumber{get;set;} 
  public DateTime MakeTime { get; set; } 
 } 
 public class Car : Vehicle 
 { 
  public int DoorNum { get; set; } 
 } 

[WebMethod] 
[XmlInclude(typeof(Car))] 
public void AddVehicle(Vehicle vehicle) 
{ 
 }  

[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 

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); 
 }