ASP.NET PDF Viewer using C#, VB/NET

As noted earlier, a common approach to implementing data-oriented procedural logic is to place it in middle-tier .NET components. Although this incurs the cost of data marshaling, it remains a viable option, even with the advent of SQL Server 2005 and CLR Integration.

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You may have noticed that regardless of whether you use SQLData or ORAData, the code generated by JPublisher suffers from what many would justifiably consider a serious drawback. The problem is that the custom classes (which are domain objects that is, objects that represent end-user business entities such as an Address, a Person, and so on) are tightly coupled with the persistence mechanism. For example, the getAddress() method in the generated domain class MyAddressAuto executes the method get_address() to retrieve the data from the database. Even if database independence is not a goal of your design, it is a good coding practice to separate out the persistence mechanism that you use to save and retrieve your domain objects from the domain objects themselves. This is a fairly involved topic in its own right, and it s beyond the scope of this book. Many well-documented frameworks (such as the Spring framework) are available, using which this objective can be achieved.

FSharp.Compiler.CodeDom, Version=1.9.2.9, Culture=neutral, PublicKeyToken=a19089b1c74d0809"/> </compilers> </system.codedom> </configuration> In the configuration file, you first configure the connection string referenced by name as NorthwindData, which you used earlier in the module that contains the data-access functionality. Connection strings describe the connection details to the database and are discussed in 15. In the second section, you need to reference the additional .NET and F# Linq assemblies that we are using in the project. These assemblies are installed in the GAC, so you can just add a reference to them. The additional assemblies, namely, the FSharp.Linq.dll file, which includes the F# Linq implementation, and northwind.dll, which includes the generated Northwind type, can simply be copied to the Bin directory of the application, and ASP.NET will discover them automatically. Finally, the web.config file also has to include a configuration of the F# CodeDom provider.

Summary

The database server is typically the most heavily taxed server in the enterprise So, although the marshaling of data causes overhead, it also unloads the procedural processing from the database server, thus freeing precious CPU resources to do other tasks Understanding this tradeoff is key to making the right decision about where to execute the logic Here are a few other factors that can influence the ultimate placement of any procedural logic: The procedural logic may already be contained within the database as a stored procedure In this case, it s generally appropriate to take advantage of CLR Integration and port the logic to a managed language The procedural logic may represent business logic that you wish to share with other applications This is typically easier to do if the logic is in the middle tier.

So far you ve seen some very simple kinds of web applications with ASP.NET and F#. In practice, ASP.NET offers an enormously powerful framework for all aspects of server-side web development. In the following sections we ll explore some additional aspects, though for full details we recommend you consult some of the excellent books dedicated to the topic of ASP.NET. Some of these books are listed at http://www.expert-fsharp.com/Topics/WebProgramming.

In this chapter, you learned what strongly typed interfaces are. You examined the JDBC standard interface, SQLData, and the Oracle extension interfaces, ORAData and ORADataFactory. You learned about the various options provided by JPublisher, a utility that generates custom classes mapping SQL objects to Java for you. You also learned, through examples, how to use JPublisher to generate custom classes that implement either SQLData or ORAData interfaces that allow you to retrieve and manipulate objects stored in the database. In the next chapter, we will examine how to use collections and references in a JDBC program.

The first line of an .aspx file usually contains special markup embedded inside <%@ ... %> ... %> containing a number of ASP.NET directives, which are instructions given to the processing environment, indicating, among other things, which scripting language is used. Table 14-4 explains the most important directives and some of their attributes.