Goals:

• Demonstrate how to create an XML Web Service.
• Demonstrate how to consume an existing XML Web Service.
• Demonstrate asynchronous calling of XML Web Service's methods.

Steps:

1. Creating an XML Web Service
   • Create a new XML Web Service project using Visual Studio (File / New / Project / Visual C# / Web / ASP.NET Web Service Application)
     • Take a look at the Service.asmx file:
       <%@ WebService Language="C#" CodeBehind="Service1.asmx.cs" Class="WebService.Service1" %>
       • The @WebService directive is required at the top.
       • The presence of the .asmx file and the @WebService directive correlate the URL address of the Web service with its implementation.
       • The Web service class you define can be included directly in the .asmx file, or in a separate file. If you use a separate file, it must be compiled into the assembly.
     • See the source code generated in the Service.cs file:
       using System;
       using System.Collections.Generic;
       using System.Linq;
       using System.Web;
       using System.Web.Services;
       
       namespace WebService
       {
           /// <summary>
           /// Summary description for Service1
           /// </summary>
           [WebService(Namespace = "http://tempuri.org/")]
           [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
           [System.ComponentModel.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";
               }
           }
       }
       • By applying the optional WebService attribute to a class that implements a Web service, you can set the default XML namespace for the Web service along with a string to describe the Web service.
         • It is highly recommended that this default namespace, which originally is http://tempuri.org, be changed before the Web service is made publicly consumable.
         • The Web service must be distinguished from other Web services that might inadvertently use the namespace as the default (http://tempuri.org/).
       • Classes that implement Web services created using ASP.NET, can optionally derive from the WebService class to gain access to the common ASP.NET objects, such as Application, Session, User, and Context (the same as in ASP.NET Web applications).
       • The WebMethod attribute must be applied to a method to give it the ability to receive Web service requests and send back responses.
     • Compile and run the project:
       
       • Note that the ASP.NET Development Server has been run.
       • The page displayed in the browser is generated by the Web server. It is not a part of the Web Service.
       • Click the 'Service Description' link.
         • The WSDL (Web Service Description Language) document is displayed.
         • This is the definition of the Web service which allows all clients (also non-.NET) to be able to use the service.
         • All Web methods (i.e. methods with the WebMethod attribute) have very strict definition of parameters and output value.
       • Click the 'HelloWorld' link:
         
         • This place allows you to test your Web method.
         • If the method has standard parameters, textboxes appear to enable to write values for input parameters.
         • The Invoke button invokes the Web method, as a result you can see the XML document with a value returned by the method.
           
         • Below the Invoke button, you can see bodies of SOAP (originally: Simple Object Access Protocol) messages used to transport input parameters and the return value.
   • Add two new methods to the Service1 class to calculate the minimum value of values passed as parameters (the first method takes 3 parameters, the second method takes an array of parameters).
     private double GetMinInternal(params double[] d)
     {
         double min = double.MaxValue;
         for (int i = 0; i < d.Length; i++)
         {
             if (d[i] < min)
             {
                 min = d[i];
             }
         }
         return min;
     }
     
     [WebMethod]
     public double GetMin(double[] d)
     {
         return GetMinInternal(d);
     }
     
     [WebMethod]
     public double GetMin3(double d1, double d2, double d3)
     {
         return GetMinInternal(d1, d2, d3);
     }
     • See the WSDL document for the Web service (run the project and click the 'Service Description' link).
       
       • Note definitions of these methods and their parameters (in particular, the definition of the ArrayOfDouble type created for the parameter of the GetMin method).
   • Add a new Web method which splits a string using a space.
     [WebMethod]
     public List<string> SplitBySpace(string s)
     {
         string[] words = s.Split(' ');
         List<string> wordsList = new List<string>(words);
         return wordsList;
     }
      
     • Check how the C# generic collection is represented in the WSDL document.
     • Test the Web method using the page generated by the Web server:
       
2. Consuming an XML Web service.
   • Open a new instance of Visual Studio (closing the project closes also the ASP.NET Development Server, so we would need the IIS to serve our web service).
   • Create a new Windows Forms project.
   • Add a Web reference to the project
     • Right click on the project in the Solution Explorer window and choose the 'Add Service Reference' option.
     • Paste the URL of your Web service (i.e. address of the .asmx file, something like: http://localhost:52828/Service1.asmx).
     • Let the tool find the Web service.
     • Set the Web reference name (e.g. 'MyFirstWebService').
       
     • Click the 'OK' button.
     • Note the new reference added in the group 'Service References' in the Solution Explorer window.
     • Right click on the new Web reference and note the 'Update Service Reference' option - crucial when the Web service has been changed.
     • Double click the new Web reference and see the content of the reference in the 'Object Browser' window
       
     • Double click any of listed types included in the reference and see the source code generated for you by Visual Studio (more precisely: by the wsdl.exe tool).
     • Add controls (a Button and a TextBox) to the Windows Forms application to demonstrate consuming a Web method.
       • Add the following code to the event handler of clicking the button:
         private void callButton_Click(object sender, EventArgs e)
         {
             MyFirstWebService.Service1SoapClient myWebService = new MyFirstWebService.Service1SoapClient();
             resultTextBox.Lines = myWebService.SplitBySpace(
                 "Lorem ipsum dolor sit amet consectetuer vel dolor Quisque hendrerit nibh").ToArray<string>();
         }
       • Run the project and click the button. Note that calling the SplitBySpace method is synchronous, i.e. it hangs the user interface.
         
3. Using one solution for an XML Web Service and a client project.
   • Visual Studio 2008 allows to easily work with both the service and the client placed in one solution. It allows even for debugging both projects in one session.
4. Drawing barcodes - synchronous and asynchronous calls of Web methods.
   • Close all projects and create new Windows Forms project.
     • Add controls to the form (5 TextBoxes, a Button, and a PictureBox):
       
     • Add a service reference to the Web service
       https://premier.ccs-inc.com/webservices/BarcodeMaker/BarcodeSvc.asmx
       
       • Click the Advanced button and check the 'Generate asynchronous operations' option:
         
     • Add the following code to the handler of clicking the button ('BarcodeService' is the name of the service reference):
       private void callButton_Click(object sender, EventArgs e)
       {
           BarcodeService.BarcodeSvcSoapClient service = new BarcodeClient.BarcodeService.BarcodeSvcSoapClient();
           byte[] buffer = service.CreateBarcode(10, 10, 10, 10,
               "Super Title", 10, true,
               textBox1.Text, textBox2.Text, textBox3.Text, textBox4.Text, textBox5.Text,
               24, 8, true, "gif");
           MemoryStream stream = new MemoryStream(buffer);
           Bitmap bmp = new Bitmap(stream);
           pictureBox.Width = bmp.Width;
           pictureBox.Height = bmp.Height;
           pictureBox.Image = bmp;
       }
     • Compile and run the application.
       • Clicking the button causes an exception:
         
       • Some settings of the communication with the service must be changed to allow receiving bigger messages. The change can be done in the App.config file (preferred method) or in the source code before calling the service's method:
         BasicHttpBinding httpBinding = service.ChannelFactory.Endpoint.Binding as BasicHttpBinding;
         httpBinding.MaxBufferSize = 1024 * 1024;
         httpBinding.MaxReceivedMessageSize = 1024 * 1024;
         httpBinding.ReaderQuotas.MaxArrayLength = 1024 * 1024;
       • The application works now:
         
       • Note, that after clicking the button application hangs, because the Web method is called synchronous.
     • Make the call asynchronous.
       • Take a look at code generated for you as a Web reference, note the existence of CreateBarcodeAsync and OnCreateBarcodeOperationCompleted methods and of CreateBarcodeCompletedEventHandler event handler.
       • Modify the code:
         private void callButton_Click(object sender, EventArgs e)
         {
             BarcodeService.BarcodeSvcSoapClient service = new BarcodeClient.BarcodeService.BarcodeSvcSoapClient();
         
             BasicHttpBinding httpBinding = service.ChannelFactory.Endpoint.Binding as BasicHttpBinding;
             httpBinding.MaxBufferSize = 1024 * 1024;
             httpBinding.MaxReceivedMessageSize = 1024 * 1024;
             httpBinding.ReaderQuotas.MaxArrayLength = 1024 * 1024;
         
             service.CreateBarcodeCompleted +=
                 new EventHandler<BarcodeClient.BarcodeService.CreateBarcodeCompletedEventArgs>(service_CreateBarcodeCompleted);
             service.CreateBarcodeAsync(10, 10, 10, 10,
                 "Super Title", 10, true,
                 textBox1.Text, textBox2.Text, textBox3.Text, textBox4.Text, textBox5.Text,
                 24, 8, true, "gif");
         }
         
         void service_CreateBarcodeCompleted(object sender, BarcodeClient.BarcodeService.CreateBarcodeCompletedEventArgs e)
         {
             byte[] buffer = e.Result;
             MemoryStream stream = new MemoryStream(buffer);
             Bitmap bmp = new Bitmap(stream);
             pictureBox.Width = bmp.Width;
             pictureBox.Height = bmp.Height;
             pictureBox.Image = bmp;
         }
       • Run and test the application, note that the application do not stop responding now.

[Source code]