Home > Articles > Web Services > XML

This chapter is from the book

Adding Classes to an XML Web Service

Once you have created your project template, Visual Studio .NET adds two classes to your project. These are the Global Class, which we will look at extensively in later hours, and the Service1 class, which we will focus on in this hour.

Service1, as the name implies, is a service. If you think of an XML Web service as a COM DLL, then a service is simply an object that is exposed by that DLL. An XML Web service project can contain many services, and we will see examples of that in Hour 23. The Global Class is a class that handles events throughout an XML Web service application, regardless of the number of services that we add to it. You will learn to use the global file in Hour 17.

When you examine a new service, you will notice that the template includes a few methods and some commented example code. The commented example code, seen in Listing 7.1 for Visual Basic and in Listing 7.2 for C#, will act as a model for every other method that you add to an XML Web service. Notice the addition of the <WebMethod> tag to the standard function declaration. This tag instructs .NET to expose this function to XML Web service consumers.

Listing 7.1 HelloWorld Method in Visual Basic

1:  <WebMethod> Public Function HelloWorld() as String
2:     HelloWorld = "Hello World"
3:  End Function

Listing 7.2 HelloWorld Method in C#

1:  [WebMethod]
2:  Public String HelloWorld()
3:   {
4:    Return "Hello World"
5:   }

Obviously, your calculator doesn't use the Hello World function, so you will leave the example code commented out, but it nicely reminds you what our calls should look like.

NOTE

If you create an XML Web service and find that some of your methods cannot be called from your client application, go back and check that you have included the <WebMethod> tag in your calls. Failure to include this tag will create methods that are exposed only to code within your XML Web service project.

Inheriting the WebService Class

When you create an XML Web service, what you are really doing is inheriting the WebService class and altering some of its methods. Two important things in your XML Web service code make this happen. The first is the inclusion of the System.Web.Services namespace, which occurs in the general declarations section of your code as follows:

Imports System.Web.Services

The second is the declaration of your service class, which has the following form:

Public Class ServiceName Inherits System.Web.Services.WebService

These two lines of code will exist in every XML Web service that you create, and they give you access to the framework of the XML Web services architecture. By building your class upon the WebService class, you can override the WebService constructors and destructors as well as add new methods.

NOTE

The Web Service Template Project in Visual Studio .NET will include WebService namespace and class declarations for you. Removing or altering these lines is a surefire way to ensure that your service doesn't function.

Calling the Constructor

By now, you have probably noticed a line in the pregenerated code that reads, "Web Services Designer Generated Code." Click on the plus sign next to that text to view the constructor function, New(). If you are in C#, you will not find the New() method but will instead find a public method with same name as your service. This method is known as the constructor in the traditional object-oriented programming model and is called whenever an object is created from your class.

This method is where you will add any initialization code that your object needs, such as setting the values of variables, connecting to a database, and so on. If you need initialization code to instantiate a custom object, place it here, after the InitializeComponent() call that .NET added for you. Listing 7.3 shows an example of initializing a custom object.

Listing 7.3 Using the New() Method to Initialize Objects

1:  Public Sub New()
2:    MyBase.New()
3:
4:    'CODEGEN: This procedure is required by the Web Services Designer
5:    'Do not modify it using the code editor.
6:    InitializeComponent()
7:
8:    Dim objConn as ADODB.Connection
9:    Set objConn = New Connection
10:  End Sub

Our four-function calculator doesn't require any initialization code, so we will leave the constructor as it is at this point. In Hours 11 and 17, we will see several examples of using the New() method in XML Web services.

NOTE

Do not add code to the New() method before the InitializeComponent() call. Code written before this line may cause serious errors at runtime.

The Dispose and Finalize Methods

Notice in our service that .NET has created a Dispose method for both Visual Basic and C# classes. This method is called when the service goes out of scope or is explicitly destroyed. This is the place in your service where you would perform garbage-collection activities, such as releasing database connections and destroying object references. This method is made public so that client code can call it before setting its reference equal to nothing.

ServiceName.Dispose()

NOTE

For those of you who haven't done much object-oriented programming, garbage collection is the term commonly used to refer to the act of reclaiming memory used by objects created in your code. It is important to destroy these objects when they are no longer needed in order to keep them from taking up valuable space in memory and causing your program to perform poorly.

.NET also allows you to add a method called Finalize. Finalize is the actual destructor of the service. In traditional object-oriented programming, this is where you would do your cleanup. Under the .NET model, however, both Dispose and Finalize can be called by the garbage collector. This is done with no guarantee as to the order in which those calls will be made or even as to when they will occur during execution. In fact, Microsoft goes so far as to caution that you cannot guarantee that the Finalize method will ever get called. Indeed, if you create a service and test for this method, you will see it occur infrequently.

Because of this, I recommend using Dispose for all your cleanup code and explicitly calling it in all your client applications. Finalize should then be used as a backup to ensure that references are dropped in the event that Dispose is not called explicitly by client code.

You will use the Dispose and Finalize methods heavily in Hours 14 and 17. Until then, just know that these methods are how you can exit your service gracefully.

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020