Home > Articles

  • Print
  • + Share This
Like this article? We recommend

Like this article? We recommend

A Web Service That Uses An Automatic Transaction

Let's create a web service that uses an automatic transaction. The web service controls a bank transaction, either a deposit or a withdrawal. The transaction is recorded in a SQL Server database. If all goes well, the web method finishes successfully, the execution thread is back in the calling method without an exception being thrown, and the transaction remains in the database. If anything goes wrong, though, the transaction won't be committed, and the transaction record won't be in the database.

Step 1: Create the Project

With Visual Studio .NET, create a new project. Select an ASP.NET web service for either a VB or a C# project. In Figure 1, a C# web service is being created.

Figure 1Figure 1 Creating a C# ASP.NET web service.


Step 2: Rename the Service and Class

Once the web service has been created, I always rename Service1.asmx to something more meaningful, and then open the source file and rename the class something other than Service1. (Visual Studio .NET names web services Service1 by default when they're created.)

For the example that I created in the preceding section, I changed the name of Service1.asmx to BankTransaction.asmx. I then opened the BankTransaction.asmx file and renamed the class from Service1 to BankTrans. There are two edits you must make in C# (only one in VB): the name of the class and the name of the constructor. The following examples show the top of the .asmx source file, and where the edits should come. The changes are marked in bold blue text.

In C#, change this:

using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Diagnostics;
using System.Web;
using System.Web.Services;

namespace BP
{
 /// <summary>
 /// Summary description for Service1.
 /// </summary>
 public class Service1 : System.Web.Services.WebService
 {
  public Service1()
  {
 //CODEGEN: This call is required by the ASP.NET Web Services Designer
   InitializeComponent();
  }

to this (replacing MyName with whatever your class is named):

using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Diagnostics;
using System.Web;
using System.Web.Services;

namespace BP
{
 /// <summary>
 /// Summary description for Service1.
 /// </summary>
 public class MyName : System.Web.Services.WebService
 {
  public MyName()
  {
 //CODEGEN: This call is required by the ASP.NET Web Services Designer
   InitializeComponent();
  }

In VB, change this:

Imports System.Web.Services

<WebService(Namespace := "http://tempuri.org/")> _
Public Class Service1
  Inherits System.Web.Services.WebService

to this (replacing MyName with whatever your class is named):

Imports System.Web.Services

<WebService(Namespace := "http://tempuri.org/")> _
Public Class MyName
  Inherits System.Web.Services.WebService

Step 3: Preparing to Add the Code

There are some things that we need to do before we can add any code. Two using statements (for C#) or two import statements (for VB) need to be added:

  • System.Data.SqlClient is needed for the SQL Server consumer namespace.

  • System.EnterpriseServices is needed for the transaction support.

System.EnterpriseServices isn't available unless you add a reference in the Visual Studio .NET Solution Explorer window. To do this, right-click the References folder and select Add Reference from the menu. In the dialog box that appears, select System.EnterpriseServices (see Figure 2).

Figure 2Figure 2 You must add the System.EnterpriseServices namespace.


Step 4: Add the Method

The last thing to do is to add the method into the .asmx file. The method that I added, Transact, is shown in Listings 1–2.

Listing 1—The Transact() Method (C#)

[WebMethod(TransactionOption=TransactionOption.RequiresNew)]
public void Transact( int nType, double dBalance,
 double dAmount, string strAccount, string strPIN )
{
 // Create the connection to the database and
 //  open it.
 SqlConnection objConnection =
  new SqlConnection( 
   "server=localhost;uid=sa;pwd=;database=WebServiceTransactions" );
 objConnection.Open();

 // Type=1 means we're adding to the balance.
 if( nType == 1 )
 {
  dBalance += dAmount;
 }
 // Otherwise we're subtracting from the balance.
 else
 {
  dBalance -= dAmount;
 }
 // But we always subtract a 15 cent transaction fee.
 dBalance -= 0.15;

 // Create the SQL statement. It's a simple INSERT.
 //  We use the string.Format() method to avoid
 //  causing the CLR to create a bunch of temp objects.
 string strSql = string.Format( "Insert Into Transactions " +
  "(Account,Balance,Amount) VALUES ('{0}',{1},{2})",
  strAccount, dBalance, dAmount );

 // Create the command object and execute the SQL.
 SqlCommand objCommand =
  new SqlCommand( strSql, objConnection );
 objCommand.ExecuteNonQuery();

 // See if the PIN is four characters long.
 if( strPIN.Length != 4 )
 {
  // If it is not, throw an exception.
  throw new Exception( "Invalid PIN" );
 }

}

Listing 2—The Transact() Method (VB)

<WebMethod(TransactionOption:=TransactionOption.RequiresNew)> _
Public Function Transact(ByVal nType As Integer, _
  ByVal dBalance As Double, ByVal dAmount As Double, _
  ByVal strAccount As String, ByVal strPIN As String)

  ' Create the connection to the database and
  '  open it.
  Dim objConnection As _
   New SqlConnection(_
   "server=localhost;uid=sa;pwd=;database=WebServiceTransactions")
  objConnection.Open()

  ' Type=1 means we're adding to the balance.
  If nType = 1 Then
    dBalance += dAmount
  Else
    ' Otherwise we're subtracting from the balance.
    dBalance -= dAmount
  End If
  ' But we always subtract a 15 cent transaction fee.
  dBalance -= 0.15

  ' Create the SQL statement. It's a simple INSERT.
  '  We use the string.Format() method to avoid
  '  causing the CLR to create a bunch of temp objects.
  Dim strSql as String = string.Format( _
    "Insert Into Transactions " + _
    "(Account,Balance,Amount) VALUES ('{0}',{1},{2})", _
    strAccount, dBalance, dAmount )

  ' Create the command object and execute the SQL.
  Dim objCommand As _
   New SqlCommand(strSql, objConnection)
  objCommand.ExecuteNonQuery()

  ' See if the PIN is four characters long.
  If strPIN.Length <> 4 Then
    ' If it is not, throw an exception.
    Throw New Exception("Invalid PIN")
  End If

End Function

Let's take a look at the Transact() method's code. The first thing it does is create a SqlConnection object, with the connection string as the only argument to the constructor.

NOTE

The SQL Server password on my server is not blank, but I removed the password to avoid security risks. A worm went around several months back, known as DispId. It attacked SQL Server for the user named sa if the password was blank.

I also heard Rob Howard mention that when Microsoft first released their Forum application's source code, it had the connection string in all of its glory, including the password.

Once the SqlConnection object has been created, the Open() method is called. If the connection string is somehow incorrect, an exception will be thrown to the calling method.

If the nType variable contains a zero, this is a deposit, and dAmount is added to dBalance. If nType is nonzero, it's a withdrawal, and dAmount is subtracted from dBalance. Notice that the parameters and results aren't checked for validity. A constraint on the balance field in the database will cause an exception to be thrown if the balance is less than zero.

A value of 15 cents is always subtracted from the balance. This is a per-transaction fee.

The SQL string we'll use is a simple insert statement. If the account number is 12345, the new balance is $54.00, and the amount that was added was $12.00, the statement will be as follows:

Insert Into Transactions (Account,Balance,Amount) 
 VALUES ('12345',54.00,12.00)

TIP

You can create the same string by concatenating strings with plus (+) symbols as follows:

C#:

strSql = "Insert Into Transactions (Account,Balance,Amount) VALUES ('" +
 strAccount + "'," +
 Convert.ToString( dBalance ) + "," + Convert.ToString( dAmount ) + ")";

VB:

strSql = "Insert Into Transactions (Account,Balance,Amount) VALUES ('" + _
 strAccount + "'," + _
 Convert.ToString( dBalance ) + "," + Convert.ToString( dAmount ) + ")"

But the Common Language Runtime (CLR) creates a number of temporary strings in the background and therefore does more work (not to mention the extra memory requirements). For this reason, the string.Format() method is preferred, since it doesn't create any of these temporary strings.

Once the SQL string is created, a SqlCommand object is created. The two parameters to the SqlCommand object's constructor are the SQL string and the SqlConnection object. With the SqlCommand object created, a call to its ExecuteNonQuery() method performs the SQL and inserts the record into the database.

The last thing that the Transact() method does is check the PIN to make sure it's four characters long. Ordinarily, the PIN would be compared to something in the database, but this is a simple demo program. If the PIN is not four characters long, an exception is thrown, thus aborting the transaction.

NOTE

This web service is available for you to use right now. The URL is http://www.aspnet-solutions.com/BankTransaction/BankTransaction.asmx.

  • + Share This
  • 🔖 Save To Your Account

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