Home > Articles

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

Like this article? We recommend

Using the Web Service from an ASP.NET Page

Once the web service has been created and compiled, we need to create an ASP.NET application that uses it. With Visual Studio .NET, simply create an ASP.NET project using VB or C#.

It's easy to add a wrapper class that takes care of all of the plumbing that needs to happen to use a web service. The wrapper class performs all of the data conversions to a Simple Object Application Protocol (SOAP) payload, which is needed to communication with the web service. To create a web service wrapper class, start by right-clicking the References folder in the Visual Studio .NET Solution Explorer. Select Add Web Reference when the menu appears. In the Add Web Reference dialog box, type the URL to the web service .asmx file followed by ?WSDL as shown in Figure 3. The ?WSDL lets the web service know that you're requesting its contract. This contract describes the behavior of the web service, and is used to create the wrapper class.

Figure 3Figure 3 To add a web service wrapper class, you must type the URL plus ?WSDL.


Once you hit Enter, the XML will be shown in the left pane (see Figure 4). This XML contains the contract description. All you have to do now is click the Add Reference button to add the wrapper class to your project.

Figure 4Figure 4 The contract XML is shown in the left pane.


The user interface for the demo application is simple. It has some text, six TextBox objects, and two buttons (see Figure 5).

Figure 5Figure 5 The user interface has six editable fields.


To use the application, you type a PIN and an amount and click the Deposit or Withdraw button to update the balance. If the web service throws an exception, it will be shown in a label below the editable fields.

NOTE

This application can be run from the URL http://www.aspnet-solutions.com/DemoWebServicesTransactions/Default.aspx.

TIP

When you're developing applications and web services at the same time, there will be occasions when the parameters to a web method might change. There's an easy way to update the web service wrapper class in an application without having to delete and re-add it. All you need to do in the application is right-click the web reference class (in the Web References folder of the Visual Studio .NET Solution Explorer window) and select Update Web Reference.

All of the transactions for a user are displayed in a DataList object. Listings 3–4 show the code behind the Default.aspx page (both the C# and VB versions).

Listing 3—The Code Behind Default.aspx (C#)

private void Page_Load(object sender, System.EventArgs e)
{
 if( !IsPostBack )
 {
  // Create an account based on the system clock.
  Account.Text = Convert.ToString( DateTime.Now.Ticks );
  // We need this for random numbers.
  Random rnd = new Random( (int) DateTime.Now.Ticks );
  // Create a random balance.
  double dBalance = (double) ( rnd.Next( 2000 ) + 5000 );
  // Convert the balance to a string.
  Balance.Text = dBalance.ToString( "$.00" );
  // Start the charge off at zero.
  Charge.Text = "$0.00";
 }

}

private void PopulateTransactionList()
{
 // Create a database connection object.
 SqlConnection objConnection =
  new SqlConnection( 
   "server=localhost;uid=sa;pwd=;database=WebServiceTransactions" );

 try
 {
  // Open the connection.
  objConnection.Open();

  // Create the SQL string.
  string strSql =
   string.Format( "select TD,Bal=CAST(Balance As varchar)," +
   "Amt=CAST(Amount As varchar) from Transactions " +
   "where Account='{0}' order by TD",
   Account.Text );

  // Create a command object.
  SqlCommand objCommand = new SqlCommand( strSql, objConnection );
  // Execute the SQL and get a SqlDataReader object back.
  SqlDataReader objReader = objCommand.ExecuteReader();
  // Set the data source for the DataList.
  TransactionList.DataSource = objReader;
  // Bind the data source to the DataList.
  TransactionList.DataBind();
  // Close the SqlDataReader object.
  objReader.Close();
 }
 catch( Exception ex )
 {
  // Let the user know of any errors.
  ErrorMessage.Text = ex.Message.ToString();
 }
 finally
 {
  // If the connection is open, close it.
  if( objConnection.State == ConnectionState.Open )
  {
   objConnection.Close();
  }
 }
}

private string ExtractExceptionMessage( 
 string strCompleteExceptionMessage )
{
 // Look for the start of the exception message that was thrown
 //  from within the Web Service
 int nStartIndex =
  strCompleteExceptionMessage.IndexOf( "invocation. ---> " ) + 17;
 // Skip the exception type (such as System.Exception :)
 nStartIndex =
  strCompleteExceptionMessage.IndexOf( ":", nStartIndex ) + 2;
 // Find the end of the exception description 
 // before the debug information.
 int nEndIndex =
  strCompleteExceptionMessage.IndexOf( " at ", nStartIndex );

 // Return the substring that contains the actual exception message.
 return( strCompleteExceptionMessage.Substring( nStartIndex,
   nEndIndex - nStartIndex ) );
}

private void DoTransaction( int nType )
{
 // Instantiate the Web Service wrapper class.
 com.aspnet_solutions.http://www.BankTrans bt =
  new com.aspnet_solutions.http://www.BankTrans();

 double dBalance = 0, dAmount = 0, dCharge = 0;
 try
 {
  // Get the balance as a double.
  dBalance = Convert.ToDouble( Balance.Text.Substring( 1, 
   Balance.Text.Length - 1 ) );
  // Get the amount as a double.
  dAmount = Convert.ToDouble( Amount.Text );
  // Get the charges as a double.
  dCharge = Convert.ToDouble( Charge.Text.Substring( 1, 
   Charge.Text.Length - 1 ) );
 }
 catch( Exception ex )
 {
  // If there was a numeric conversion exception,
  //  we'll catch it here, show the error, and
  //  return to caller.
  ErrorMessage.Text = ex.Message.ToString();
  return;
 }
 try
 {
  // Call the Transact() method.
  bt.Transact( nType, dBalance, dAmount,
   Account.Text, PIN.Text );
 }
 catch( Exception ex )
 {
  ErrorMessage.Text =
   ExtractExceptionMessage( ex.Message.ToString() );
  return;
 }

 // Show the results.
 ErrorMessage.Text = "Transaction success";

 // If a deposit, add the amount.
 if( nType == 1 )
 {
  dBalance += dAmount;
 }
 // Otherwise subtract the amount.
 else
 {
  dBalance -= dAmount;
 }
 // Subtract the transaction charge from the balance.
 dBalance -= 0.15;
 // Add the transaction charge to the charge variable.
 dCharge += 0.15;

 // Set the user interface strings to the updated values.
 Balance.Text = dBalance.ToString( "$.00" );
 Amount.Text = "";
 Charge.Text = dCharge.ToString( "$.00" );

 PopulateTransactionList();
}

private void Deposit_Click(object sender, System.EventArgs e)
{
 DoTransaction( 1 );
}

private void Withdraw_Click(object sender, System.EventArgs e)
{
 DoTransaction( 0 );
}

Listing 4—The Code Behind Default.aspx (VB)

Private Sub Page_Load(ByVal sender As System.Object, _
 ByVal e As System.EventArgs) Handles MyBase.Load
  If Not IsPostBack Then
    ' Create an account based on the system clock.
    Account.Text = Convert.ToString(DateTime.Now.Ticks)
    ' We need this for random numbers.
    Dim rnd As New Random(DateTime.Now.Ticks)
    ' Create a random balance.
    Dim dBalance As Double = (rnd.Next(2000) + 5000)
    ' Convert the balance to a string.
    Balance.Text = dBalance.ToString("$.00")
    ' Start the charge off at zero.
    Charge.Text = "$0.00"
  End If
End Sub

Private Sub PopulateTransactionList()
  ' Create a database connection object.
  Dim objConnection As _
   New SqlConnection(_
    "server=localhost;uid=sa;pwd=;database=WebServiceTransactions")

  Try
    ' Open the connection.
    objConnection.Open()

    ' Create the SQL string.
    Dim strSql As String = _
     String.Format("select TD,Bal=CAST(Balance As varchar)," + _
     "Amt=CAST(Amount As varchar) from Transactions " + _
     "where Account='{0}' order by TD", _
     Account.Text)

    ' Create a command object.
    Dim objCommand As New SqlCommand(strSql, objConnection)
    ' Execute the SQL and get a SqlDataReader object back.
    Dim objReader As SqlDataReader = objCommand.ExecuteReader()
    ' Set the data source for the DataList.
    TransactionList.DataSource = objReader
    ' Bind the data source to the DataList.
    TransactionList.DataBind()
    ' Close the SqlDataReader object.
    objReader.Close()
  Catch ex As Exception
    ' Let the user know of any errors.
    ErrorMessage.Text = ex.Message.ToString()
  Finally
    ' If the connection is open, close it.
    If objConnection.State = ConnectionState.Open Then
      objConnection.Close()
    End If
  End Try

End Sub

Private Function ExtractExceptionMessage(_
 ByVal strCompleteExceptionMessage As String) As String
  ' Look for the start of the exception message that was thrown
  '  from within the Web Service
  Dim nStartIndex As Integer = _
   strCompleteExceptionMessage.IndexOf("invocation. ---> ") + 17
  ' Skip the exception type (such as System.Exception :)
  nStartIndex = _
   strCompleteExceptionMessage.IndexOf(":", nStartIndex) + 2
  ' Find the end of the exception description before the 
  '  debug information.
  Dim nEndIndex As Integer = _
   strCompleteExceptionMessage.IndexOf(" at ", nStartIndex)

  ' Return the substring that contains the actual exception message.
  Return (strCompleteExceptionMessage.Substring(nStartIndex, _
   nEndIndex - nStartIndex))
End Function

Private Sub DoTransaction(ByVal nType As Integer)
  ' Instantiate the Web Service wrapper class.
  Dim bt as _
   new com.aspnet_solutions.http://www.BankTrans()

  Dim dBalance As Double = 0, dAmount As Double = 0, _
   dCharge As Double = 0
  Try
    ' Get the balance as a double.
    dBalance = Convert.ToDouble(Balance.Text.Substring(1, _
     Balance.Text.Length - 1))
    ' Get the amount as a double.
    dAmount = Convert.ToDouble(Amount.Text)
    ' Get the charges as a double.
    dCharge = Convert.ToDouble(Charge.Text.Substring(1, _
     Charge.Text.Length - 1))
  Catch ex As Exception
    ' If there was a numeric conversion exception,
    '  we'll catch it here, show the error, and
    '  return to caller.
    ErrorMessage.Text = ex.Message.ToString()
    Return
  End Try

  Try
    ' Call the Transact() method.
    bt.Transact( nType, dBalance, dAmount, _
     Account.Text, PIN.Text )
  Catch ex As Exception
   ErrorMessage.Text = ExtractExceptionMessage(ex.Message.ToString())
    Return
  End Try

  ' Show the results.
  ErrorMessage.Text = "Transaction success"

  ' If a deposit, add the amount.
  If nType = 1 Then
    dBalance += dAmount
  Else
    ' Otherwise subtract the amount.
    dBalance -= dAmount
  End If
  ' Subtract the transaction charge from the balance.
  dBalance -= 0.15
  ' Add the transaction charge to the charge variable.
  dCharge += 0.15

  ' Set the user interface strings to the updated values.
  Balance.Text = dBalance.ToString("$.00")
  Amount.Text = ""
  Charge.Text = dCharge.ToString("$.00")

  PopulateTransactionList()

End Sub

Private Sub Deposit_Click(ByVal sender As System.Object, _
 ByVal e As System.EventArgs) Handles Deposit.Click
  DoTransaction(1)
End Sub

Private Sub Withdraw_Click(ByVal sender As System.Object, _
 ByVal e As System.EventArgs) Handles Withdraw.Click
  DoTransaction(0)
End Sub

The code in Listings 3–4 is fairly straightforward, but let's talk through it right now so that you understand what I've done.

The Page_Load() Method

The Page_Load() method initializes three of the user interface TextBox objects the first time that the page is loaded. The Account TextBox object is initialized with the system ticks, and this is used to simulate an account number. A Random object is then instantiated so that a random number can be obtained. This random number (plus 5,000) will be the starting bank balance, and the value will be converted to a text string and placed in the Balance TextBox object. Finally, the Charge TextBox object will be initialized to $0.00.

The PopulateTransactionList() Method

The PopulateTransactionList() method queries the database for all records that are in the currently displayed account. When a user first loads the page, no transactions will be shown, because the user account has just been created based on the system ticks.

The first thing that happens in this method is that a SqlConnection object is created. The only argument to its constructor is the connection string (with the password removed here in the text). A try/catch/finally construct handles any database errors that are thrown. Inside the try block, the connection is opened with the SqlConnection.Open() method. Figure 6 shows the Transactions table.

Figure 6Figure 6 The Transactions table.


A SQL string is formed that will get all of the transactions for the currently displayed account number. The SQL is a little more complicated than it might need to be, but this is because we want to make sure that the money amounts have two decimal places. If we weren't concerned about the formatting, the following SQL statement would work for all records for the 12345 account:

Select TD,Balance,Amount from Transactions where Account='12345'

Even through the Balance and Amount fields are of the money type in the database, when they are bound to the DataList object they may not have two decimal places. For that reason, we add some extra T-SQL code as follows:

Bal=CAST(Balance As varchar)

and

Amt=CAST(Amount As varchar)

The statement, with these two additions, is now as follows:

Select TD, Bal=CAST(Balance As varchar), Amt=CAST(Amount As varchar)
 from Transactions where Account='12345'

Notice in the code, though, that the string.Format() method is used to prevent additional string objects from being created in the background.

Once we have the SQL string, we create a SqlCommand object. It has two arguments: the SQL string and the SqlConnection object. The SqlCommand object's ExecuteReader() method is called, which in turn returns a SqlDataReader object that contains all the records matching the account number.

The DataList object is named TransactionList. This object's DataSource property is set to the SqlDataReader, and then the DataBind() method is called. This will populate the records to the DataList object. Finally, the SqlDataReader object is closed.

The catch block takes the exception message and places it into the user interface Label named ErrorMessage. The finally block closes the database connection if it is open.

The ExtractExceptionMessage() Method

The ExtractExceptionMessage() method is needed because when the web service wrapper class throws an exception, there is a lot of information in addition to the actual exception message. This method extracts what's between "invocation ---> " and " at ". This is the effective exception that was thrown within the web service.

The DoTransaction() Method

This method instantiates the web service wrapper class, calls the Transact() web method, and then displays the results for the user.

The first thing that happens is the instantiation of the web service, as shown below:

C#:

com.aspnet_solutions.http://www.BankTrans bt = 
 new com.aspnet_solutions.http://www.BankTrans();

VB:

Dim bt As New com.aspnet_solutions.http://www.BankTrans()

Three variables of the type double are declared, and their values are initialized to zero. A try/catch construct will take care of any numeric conversion errors. These will happen if the user interface TextBox objects contain non-numeric characters, or no characters at all. If everything goes well, though, the Convert.ToDouble() method converts the text in the TextBox objects to numeric values. If an exception was thrown, the user is notified of the error, with the exception message placed into the ErrorMessage Label object.

Another try/catch construct catches exceptions that the Transact() web method throws. The call to Transact() is made with five parameters: the transaction type, the balance, the amount, the account number, and the PIN. Possible exceptions that the web method might throw are that the PIN is not four characters, or the balance is below zero. If an exception is caught, the real exception message is extracted using the ExtractExceptionMessage() method, the ErrorMessage Label is set to this text, and a Return is executed.

If everything goes okay, though, the only thing left to do is to update the user interface objects. The dBalance variable is updated using the dAmount variable, and an additional 15 cents is subtracted for the transaction charge. The dCharge variable gets an additional 15 cents to reflect the total transaction charges. The Balance, Amount, and Charge TextBox objects are updated to reflect the new values. Finally, a call to PopulateTransactionList() is made to show the list of transactions for this user.

The Deposit_Click() Method

The Deposit_Click() method simply calls the DoTransaction() method with the argument of 1 so that a deposit is made.

The Withdraw_Click() Method

The Withdraw_Click() method calls the DoTransaction() method with the argument of 0 so that a withdrawal is made.

  • + 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