Home > Articles

This chapter is from the book

Building a Managed C++ Component with a C# Client

Today, to illustrate how each different interaction scenario might work, you'll build not one, but three component/application combinations. The first one re-creates the component you built yesterday as a pure managed C++ component, and builds a C# and/or VB.NET client that accesses it. Next, you'll re-create the component using either C# or VB.NET, and access it using a managed C++ client. Finally, you'll access the C#/VB.NET component using an unmanaged C++ client.

Building the Managed C++ Component

To start the first of these projects, follow these steps:

  1. Create a new Managed C++ Class Library project and name it MgdTaxCalc.

  2. Open the MgdTaxCalc.h header file.

  3. Replace the class name Class1 with the new class name, CTaxCalculator.

  4. Add a new member function to the CTaxCalculator class (you'll need to expand the MgdTaxCalc namespace node in the Class View pane). Specify the function return type as double, the name as CalculateTaxes, and add two parameters. For the first parameter, specify the type as double and the name as dbPurchaseAmt. For the second parameter, specify the type as String* and the name as strCategory. Specify the function access as public.

  5. Edit the function in the header file, adding the code in Listing 21.1.

  6. Listing 21.1 The CalculateTaxes Function

    double CalculateTaxes(double dbPurchaseAmt, String* strCategory)
    {
      // Declare the array of tax categories
      String* strCategories[] = {S"food", S"clothing", S"music"};
      // Declare the array of tax rates
       double dbRates[] = {0.0725, 0.0835, 0.081};
      // Loop through the categories
      for (int i=0; i < 3; i++)
      {
        // Is this the category purchased?
        if (strCategory == strCategories[i])
        {
          // Yes, calculate the taxes due
          return dbPurchaseAmt * dbRates[i];
        }
      }
      // Couldn't find the category purchased, return 0
      return 0;
    }

That's all for the managed C++ component. The code is basically the same as the unmanaged component from yesterday, only uses managed strings and returns the amount of taxes to charge as the result value.

Building the C# or VB.NET Client

The next step in this example adds either the C# or VB.NET client application to this solution. The client application duplicates the functionality from the managed C++ client application that you implemented yesterday. To build this client, follow these steps:

  1. In the Solution Explorer pane, select and right-click the solution node at the top of the tree. Select Add, New Project from the context menu.

  2. Click either Visual Basic Projects or Visual C# Projects on the left side of the Add New Project dialog. Select Console Application on the right side of the dialog (this application type is available for both VB.NET and C# projects). If you are creating a Visual Basic project, name it VBClient. For a C# project, name it CSClient. Click OK to create the project.

  3. In the Solution Explorer pane, select and right-click the References node in the new project you just created. Select Add Reference from the context menu.

  4. In the Add Reference dialog, select the Projects tab. You should see your managed C++ component project (MgdTaxCalc) in the project list. Click the project and then click Select. Click OK to add the reference to the project.

  5. If you created a C# project, open the Class1.cs file. If you created a VB project, open the Module1.vb file.

  6. If you created a C# project, edit the main function, adding the code in Listing 21.2. If you created a VB project, edit the main function, adding the code in Listing 21.3.

  7. Listing 21.2 The C# Client Main Function

    static void Main(string[] args)
    {
      //
      // TODO: Add code to start application here
      //
      MgdTaxCalc.CTaxCalculator pGetTax = new MgdTaxCalc.CTaxCalculator();
    
      double dbPurchaseAmt, dbTaxAmt, dbTotalDue;
    
      // Create the string for the category being purchased
      String strCategory = "clothing";
    
      // Specify the purchase amount
      dbPurchaseAmt = 45.0;
      // Get the amount of taxes to collect
      dbTaxAmt = pGetTax.CalculateTaxes(dbPurchaseAmt, strCategory);
      if (dbTaxAmt > 0.0)
      {
        // Calculate the total due
        dbTotalDue = dbPurchaseAmt + dbTaxAmt;
        // Display the category being purchased
        Console.WriteLine(strCategory);
        // Display the purchase amount
        Console.Write("Purchase Amount = ");
        Console.WriteLine(dbPurchaseAmt.ToString("c"));
        // Display the tax due
        Console.Write("      Tax = ");
        Console.WriteLine(dbTaxAmt.ToString("c"));
        // Display the total amount
        Console.Write("   Total Due = ");
        Console.WriteLine(dbTotalDue.ToString("c"));
      }
    }

    Listing 21.3 The VB.NET Client Main Function

    Sub Main()
      Dim pGetTax As MgdTaxCalc.CTaxCalculator
      pGetTax = New MgdTaxCalc.CTaxCalculator()
    
      Dim dbPurchaseAmt As Double
      Dim dbTaxAmt As Double
      Dim dbTotalDue As Double
    
      ' Create the string for the category being purchased
      Dim strCategory As String
      strCategory = "clothing"
    
      ' Specify the purchase amount
      dbPurchaseAmt = 45
      ' Get the amount of taxes to collect
      dbTaxAmt = pGetTax.CalculateTaxes(dbPurchaseAmt, strCategory)
      If (dbTaxAmt > 0) Then
        ' Calculate the total due
        dbTotalDue = dbPurchaseAmt + dbTaxAmt
        ' Display the category being purchased
        Console.WriteLine(strCategory)
        ' Display the purchase amount
        Console.Write("Purchase Amount = ")
        Console.WriteLine(dbPurchaseAmt.ToString("c"))
        ' Display the tax due
        Console.Write("      Tax = ")
        Console.WriteLine(dbTaxAmt.ToString("c"))
        ' Display the total amount
        Console.Write("   Total Due = ")
        Console.WriteLine(dbTotalDue.ToString("c"))
      End If
    
    End Sub
  8. In the Solution Explorer pane, select and right-click the client project that you created. Select Set as Startup Project from the context menu.

Now you should be able to compile and run your example application, producing the output in Figure 21.2. You can also repeat these steps to build the client application, using the other language than what you used (assuming that you have Visual Studio and not just Visual C++) so that you have both languages available for your use.

Figure 21.2. The running

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