ASP.NET web service

Web services

A Web service is a web-based feature that can be obtained by a web app through a web network protocol. W eb service development consists of the following three main areas:

• Create a web service
• Create a proxy server
• Use a web service

Create a web service

A web service is a web app that basically consists of a class that contains multiple methods that can be called by other apps, and it also uses a hidden code structure such as an ASP.NET web page, but it does not have a user interface.

To better understand this concept, let's create a web service that provides stock price information. C lients of the service can query the relevant name and price through the stock label. T o simplify this example, we set the stock price to a fixed value and save it in a two-dimensional list. This web service consists of three methods:

• A default HelloWorld method
• A GetName method
• A GetPrice method

Take the following steps to create the service:

Step (1): Select File -gt; New - Web Site in Visual Studio, and then select ASP.NET Web Service.

Step (2): A web service file named Service.asmx and its code are hidden, and service.cs is created under the App_Code path of the project.

Step (3): Change the file name to StockService.asmx and StockService .cs.

Step (4): The .asmx file simplifies a WebService directive as follows:

<%@ WebService Language="C#" CodeBehind="~/App_Code/StockService.cs" 
Class="StockService" %> 

Step (5): Open the StockService .cs file, which generates the code that is the underlying code for the Hello World service. T he default web service code is as follows:

    using System;
    using System.Collections;
    using System.ComponentModel;
    using System.Data;
    using System.Linq;

    using System.Web;
    using System.Web.Services;
    using System.Web.Services.Protocols;

    using System.Xml.Linq;

    namespace StockService
    {
       // <summary>
       // Summary description for Service1
       // <summary>

       [WebService(Namespace = "http://tempuri.org/")]
       [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
       [ToolboxItem(false)]

       // To allow this Web Service to be called from script, 
       // using ASP.NET AJAX, uncomment the following line. 
       // [System.Web.Script.Services.ScriptService]

       public class Service1 : System.Web.Services.WebService
       {
          [WebMethod]

          public string HelloWorld()
          {
             return "Hello World";
          }
       }
    }

Step (6): Modify the code in the file to add a two-dimensional pointer to a string that stores the names and prices of each stock, and write two web methods to get stock information as follows;

    using System;
    using System.Linq;

    using System.Web;
    using System.Web.Services;
    using System.Web.Services.Protocols;

    using System.Xml.Linq;

    [WebService(Namespace = "http://tempuri.org/")]
    [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]

    // To allow this Web Service to be called from script, 
    // using ASP.NET AJAX, uncomment the following line. 
    // [System.Web.Script.Services.ScriptService]

    public class StockService : System.Web.Services.WebService
    {
       public StockService () {
      //Uncomment the following if using designed components 
      //InitializeComponent(); 
       }

       string[,] stocks =
       {
          {"RELIND", "Reliance Industries", "1060.15"},
          {"ICICI", "ICICI Bank", "911.55"},
          {"JSW", "JSW Steel", "1201.25"},
          {"WIPRO", "Wipro Limited", "1194.65"},
          {"SATYAM", "Satyam Computers", "91.10"}
       };

      [WebMethod]
       public string HelloWorld() {
          return "Hello World";
       }

      [WebMethod]
       public double GetPrice(string symbol)
       { 
          //it takes the symbol as parameter and returns price
          for (int i = 0; i < stocks.GetLength(0); i++)
          {
             if (String.Compare(symbol, stocks[i, 0], true) == 0)
             return Convert.ToDouble(stocks[i, 2]);
          }

          return 0;
       }

       [WebMethod]
       public string GetName(string symbol)
       {
          // It takes the symbol as parameter and 
          // returns name of the stock
          for (int i = 0; i < stocks.GetLength(0); i++)
          {
             if (String.Compare(symbol, stocks[i, 0], true) == 0)
             return stocks[i, 1];
          }

          return "Stock Not Found";
       }
    }

Step (7): Running the web service app gives a web service test page on which we can test the service method.

Step (8): Click on a method name to confirm that it is running correctly.

Step (9): To detect the GetName method, provide one of the stock tags that has been defined and, correctly, return the name of the relevant stock.

Use a Web service

To use the web service, we create a Web site under the same solution, just right-click the solution name on Solution Manager, and the web page called by the web service should have a control management to display the returned results and two control buttons, one for returning another for starting the call to the service.

The web app's files are as follows:

    <%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="wsclient._Default" %>

    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

    <html xmlns="http://www.w3.org/1999/xhtml" >

       <head runat="server">
          <title>
             Untitled Page
          </title>
       </head>

       <body>

          <form id="form1" runat="server">
             <div>

                 <h3>Using the Stock Service</h3>

                 <br /> <br />

                 <asp:Label ID="lblmessage" runat="server"></asp:Label>

                 <br /> <br />

                 <asp:Button ID="btnpostback" runat="server" onclick="Button1_Click" Text="Post Back" style="width:132px" />

                 <asp:Button ID="btnservice" runat="server" onclick="btnservice_Click"  Text="Get Stock" style="width:99px" />

              </div>
          </form>

       </body>
    </html>

The code for the web app is as follows:

    using System;
    using System.Collections;
    using System.Configuration;
    using System.Data;
    using System.Linq;

    using System.Web;
    using System.Web.Security;
    using System.Web.UI;
    using System.Web.UI.HtmlControls;
    using System.Web.UI.WebControls;
    using System.Web.UI.WebControls.WebParts;

    using System.Xml.Linq;

    //this is the proxy
    using localhost;

    namespace wsclient
    {
       public partial class _Default : System.Web.UI.Page
       {
           protected void Page_Load(object sender, EventArgs e)
           {
               if (!IsPostBack)
               {
                   lblmessage.Text = "First Loading Time: " +  DateTime.Now.ToLongTimeString
               }
               else
               {
                   lblmessage.Text = "PostBack at: " + DateTime.Now.ToLongTimeString();
               }
           }

           protected void btnservice_Click(object sender, EventArgs e)
           {
               StockService proxy = new StockService();
               lblmessage.Text = String.Format("Current SATYAM Price:{0}",
               proxy.GetPrice("SATYAM").ToString());
           }
      }
    }

Create a proxy server

A proxy server is a substitute for a web service code. B efore we can use the web service, we must create a proxy server. T his proxy server is registered by the client app. T he client app then implements a call to the web service to make it look like it's using a local method.

The proxy server will call and send the call to the server in the appropriate format as if it were a SOAP request. S OAP supports Simple Object Access Protocol. This protocol applies to web service data exchange.

When this server responds and returns a SOAP package to the client, the proxy server presents everything to the client application.

Web btnservice_click be added to your application before calling a Web service using the web app. This transparently creates a proxy class that can be used by btnservice_click events.

    protected void btnservice_Click(object sender, EventArgs e)
    {
       StockService proxy = new StockService();
       lblmessage.Text = String.Format("Current SATYAM Price: {0}", 
       proxy.GetPrice("SATYAM").ToString());
    }

Take these steps to create a proxy:

Step (1): Right-click 'Add Web Reference' at the entrance to the solution Explorer's web app.

Step (2): Selecting 'Web Services in this solution' returns the stock service reference we wrote.

Step (3): Click on the service to open the test page and create the proxy by default as 'localhost', which you can rename. C lick 'Add Reference' to add a proxy to the client application.

Add the following statement to your code to include the agent:

using localhost;