Figure 10-3. Data loaded into an intermediate object, followed by the web form in VB.NET

Generator PDF417 in VB.NET Figure 10-3. Data loaded into an intermediate object, followed by the web form

Figure 10-3. Data loaded into an intermediate object, followed by the web form
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This means that, in general, you can expect similar performance characteristics from the DataSet and business objects. However, business objects are often actually more lightweight than the ADO.NET DataSet object. This is because business objects are specific to the data they contain, and don t need to retain all the metadata required by the DataSet object. Better yet, business objects provide access not only to the application s data, but also to its business logic. As discussed in 1, business objects can be thought of as smart data. They encapsulate the business logic and the data so that the UI doesn t need to worry about potential data misuse. Overall, business objects provide the high-scalability characteristics of the DataSet, without the overhead. They offer a better use of database connections than the data reader, though at the cost of some performance in certain situations. When compared to both other technologies, business objects enable a much higher level of reuse and easier long-term maintenance, making them the best choice overall.
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The Achilles heel of web development is state management. The original design of web technology was merely for document viewing, not the myriad purposes for which it s used today. Because of this, the issue of state management was never thought through in a methodical way. Instead, state management techniques have evolved over time in a relatively ad hoc manner. Through this haphazard process, some workable solutions have evolved, though each requires trade-offs in terms of performance, scalability, and fault tolerance. The primary options at your disposal are as follows: State is maintained on the web server. State is transferred from server to client to server on each page request. State is stored in temporary files or database tables. Whether you use a DataSet, a data reader, or business objects to retrieve and update data is immaterial here ultimately, you re left to choose one of these three state management strategies. Table 10-1 summarizes the strengths and weaknesses of each.
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CHAPTER 10 s WEB FORMS UI
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Table 10-1. State Management Strategies
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State stored on web server
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Strengths
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Easy to code and use. Works well with business objects.
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Weaknesses
Use of global fields/data is poor programming practice. Scalability and fault tolerance via a web farm requires increased complexity of infrastructure. Hard to code, requires a lot of manual coding to implement. Performance can be a problem over slow network links. Increased load on database server since state is retrieved/stored on each page hit. Requires manual coding to implement. Data cleanup must be implemented to deal with abandoned state data.
State transferred to/from client
Scalability and fault tolerance are easily achieved by implementing a web farm. Scalability and fault tolerance are easily achieved by implementing a web farm. A lot of state data or very complex data can be easily stored.
State stored in file/database
As you can see, all of these solutions have more drawbacks than benefits. Unfortunately, in the more than ten years that the Web has been a mainstream technology, no vendor or standards body has been able to provide a comprehensive solution to the issue of dealing with state data. All you can do is choose the solution that has the lowest negative impact on your particular application. Let s go into some more detail on each of these techniques, in the context of using business objects behind web pages.
State on the Web Server
First, you can choose to keep state on the web server. This is easily accomplished through the use of the ASP.NET Session object, which is a name/value collection of arbitrary data or objects. ASP .NET manages the Session object, ensuring that each user has a unique Session, and that the Session object is available to all Web Forms code on any page request. This is by far the easiest way to program web applications. The Session object acts as a global repository for almost any data that you need to keep from page to page. By storing state data on the web server, you enable the type of host-based computing that has been done on mainframes and minicomputers for decades. As I ve already expressed, however, there are drawbacks. Session is a global repository for each user, but as any experienced programmer knows, the use of global fields is very dangerous and can rapidly lead to code that s hard to maintain. If you choose to use Session to store state, you must be disciplined in its use to avoid these problems. The use of Session also has scalability and fault tolerance ramifications.
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