ASP.NET Web Services

 A unit of managed code installed under IIS that can be remotely invoked using HTTP.

Similar Technologies  DCOM  CORBA  EJB (Enterprise Java Beans)  All are tied to a specific language or a proprietary protocol.

Introducing Web Services  Language Agnostic.  Can be called by any program that can parse XML and use HTTP.  Can be called from Web Forms as well as Windows Forms.

Supporting Technologies  Web Service Description Language (WSDL)  A wire protocol (HTTP GET, HTTP POST, or SOAP)  A discovery Service (*.disco files)  Proxies  IIS

Building a Simple Web Service  Select C# Projects->ASP.NET Web Service.  Automatically creates a virtual directory under IIS.  Can test from within the program without using a client.

[WebMethod] Attribute  This attribute must be applied to each method you wish to expose to the outside world through HTTP.  May have optional parameters such as: –Description –EnableSessionn (false by default) –MessageName  Adds a description to the WSDL Contract. [WebMethod(Description=“Returns an integer between 0 and the parameter”)] public int ReturnAnInt (int MaxValue) { return new Random().Next(MaxValue); }

WebService Base Class  Not required to derive from this class, can inherit directly from object.  Adds functionality such that a web service can interact with the same types used by the ASP.NET object model: –Application Object –Context Object –Server Object –Session Object –User Object

WSDL  Web Service Description Language  Contract between the client and the web service, that defines the interaction –Function names. –Parameters and their types. –Syntax of various wire protocols.  System.Web.Services.Description contains types that allow you to programmatically manipulate the WSDL.

SOAP  Simple Object Access Protocol  XML Based  Types –ADO.NET DataSets –Complex Arrays –Custom Types  Binding: </binding>

Proxies  Creates a class that contains the interface for your web service  Using wsdl.exe C:\wsdl.exe out:c:\testproxy.cs  Using Visual Studio.NET –Add Web Reference

Proxies  Adds Asynchronous and Synchronous versions of each exposed Web Method  Looks and feels like the Web Service is a class in the client application

Advanced  Serializing Custom Types  Using Session to maintain information from previous calls  Connecting to a Database

Serializing Custom Types using System; using System.Xml.Serialization; namespace CarsWebService { //Tells the serializer to generate the proper XML tags for a car type //Tells the serializer to generate the proper XML tags for a car type [XmlInclude(typeof(Car))] [XmlInclude(typeof(Car))] public class Car public class Car { public string name; public string name; public int maxSpeed; public int maxSpeed; public Car(){} public Car(){} public Car(string n, int s) public Car(string n, int s) { name = n; name = n; maxSpeed = s; maxSpeed = s; } }} //The XML Serializer will only serialize public members or properties that expose those members

Session State namespace TestService { public class TestService1 : System.Web.WebService { public TestService1() {InitializeComponent(); Session.Add(“TestDataSet”, null); }[WebMethod] public void TestMethod(DataSet ds) { Session[“TestDataSet”] = ds; }}}

Database Connections  Allows for Database client software to reside on one machine.  Allows for one consistent interface to the database.  Allows the business rules to be separate from the client

Discovery Service Protocol  Describes each Web Service in a given virtual directory. .disco file is part of the client project  C:\disco  C:\disco <discovery xmlns:xsd=" xmlns:xsi=" xmlns=" <contractRef ref=" docRef=" xmlns=" /> <soap address=" xmlns:q1="hpsiserver.hpsionline.com" binding="q1:BuildRunServiceSoap" xmlns=" />

Distributing over a network Database Web Service Web Form Windows Form

Creating a Web Service Project  Choose ASP.NET Web Service  The project is created in C:\Inetpub\wwwroot\projectname  The web service file is.asmx –Code behind is in.asmx.cs file  IIS must be installed

Using a Web Service  Add a web reference –The proxy is hidden in the Web Reference  Create an instance of the proxy class  Use the proxy instance as you would a normal class instance

Conclusion  Web Services are cool!  Can be used to allow dissimilar systems to communicate  Easy to implement  Easy to learn how to use  Fairly Slow