Building Distributed Applications with Visual Basic

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If you use COM+ and its services to build distributed applications for Windows 2000, you'll find yourself in environment like the one shown in Figure 1-8. As you can see, there's a lot to learn.

Of all the COM-enabled development tools on the market, Visual Basic offers the highest levels of productivity. Visual Basic 3 and Visual Basic 4 both offered modest advancements in the product's COM-awareness, but Visual Basic 5 really made this development tool a viable option for building components for COM-based systems. Visual Basic 6 added even more support for COM and MTS development.

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Figure 1-8 You can create middle-tier components using COM+ and Visual Basic.

Take a moment to consider the following questions. What is your perception of Visual Basic? Does it provide a viable option for writing the code for a large-scale application? Why are you reading this book? Respond to the following questions by choosing Visual Basic, C++, or Structured Query Language (SQL):

  • Which language is the easiest for writing business logic?
  • Which language offers the lowest cost of code maintenance?
  • Which language offers the fastest means to enhance an existing application?
  • Which is the best language for people without a classic computer science background?

Many designers and project leads would automatically answer "Visual Basic" for all these questions. But Visual Basic is in no way a cure-all language. In some cases, C++ or some other language would be a better choice for a specific component. For example, many COM interfaces, such as those exposed by OLE DB, can be readily accessed only through C++, which means that some components should be written in C++. However, companies have many opportunities to use Visual Basic in a distributed application. One of the greatest opportunities is for writing business logic and data access code for distributed objects in the middle tier of a large information system.

In the days of two-tier systems, Visual Basic was an incredibly popular tool for building the user interface. Companies used Visual Basic to build forms-based applications that ran on the desktop. Visual Basic programmers spent a good deal of their time designing forms and writing the code to deal with user interaction. Things sure have changed. More and more companies have switched to building browser-based applications for the presentation tier using HTML-based development tools such as Visual InterDev. In some ways, Visual Basic programmers have been looking for a new home.

The bright new future for Visual Basic programmers is in building nonvisual components for the middle tier. Companies that thought COM programming required C++ are changing their tune. An increasing number of shops are trying to write as much middle-tier code with Visual Basic as possible. And what's more, Visual Basic programmers have lots of support from the folks who are building the platform. The architects and implementers who have put COM+ together see Visual Basic programmers as their biggest customer.

Summary

This chapter has provided a high-level overview of the things you need to know to build large-scale information systems with COM+ and Windows 2000. Many companies demand multitier applications to reach their employees, vendors, and customers. But anyone who's involved in multitier development will tell you that building a distributed application is an incredibly challenging undertaking.

The designers of COM+ have tried their best to hide the complexities of building distributed applications. What's more, Visual Basic goes a long way toward hiding many of the complexities of COM and COM+. But however "hidden" some of the intricacies of the infrastructure are, you still can't get by without a solid understanding of the core technologies and the platform's interrelated subsystems. The more you know about the underlying infrastructure the better. The philosophy you should adopt is that you will be partnering with COM+ and Windows 2000. They will do some of the work, and so will you. The secret is to let them do what they do best—provide low-level infrastructure. With this infrastructure solidly behind you, you'll be able to spend more time doing what you need to do—writing the business logic and data access code that is specific to your application.



Programming Distributed Applications with COM+ and Microsoft Visual Basic 6.0
Programming Distributed Applications with Com and Microsoft Visual Basic 6.0 (Programming/Visual Basic)
ISBN: 1572319615
EAN: 2147483647
Year: 2000
Pages: 70
Authors: Ted Pattison

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