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While this syntax does remove the need to manually wrap disposable objects within try/finally logic, the C# using keyword unfortunately now has a double meaning (importing namespaces and invoking a Dispose() method). Nevertheless, when you are working with .NET types that support the IDisposable interface, this syntactical construct will ensure that the object being used will automatically have its Dispose() method called once the using block has exited. Also, be aware that it is possible to declare multiple objects of the same type within a using scope. As you would expect, the compiler will inject code to call Dispose() on each declared object: static void Main(string[] args) { Console.WriteLine("***** Fun with Dispose *****\n"); // Use a comma-delimited list to declare multiple objects to dispose. using(MyResourceWrapper rw = new MyResourceWrapper(), rw2 = new MyResourceWrapper()) { // Use rw and rw2 objects. } }

Theming involves transforming the data that has been retrieved, manipulated, or created into HTML (or XML or other output format). Drupal will use the theme the administrator has selected to give the web page the correct look and feel. The resulting output is then sent to the web browser (or other HTTP client).

At this point, we have seen two different approaches to constructing a class that cleans up internal unmanaged resources. On the one hand, you can override System.Object.Finalize(). Using this technique, you have the peace of mind that comes with knowing the object cleans itself up when garbage-collected (whenever that may be) without the need for user interaction. On the other hand, you can implement IDisposable to provide a way for the object user to clean up the object as soon as it is finished. However, if the caller forgets to call Dispose(), the unmanaged resources may be held in memory indefinitely.

As you might suspect, it is possible to blend both techniques into a single class definition. By doing so, you gain the best of both models. If the object user does remember to call Dispose(), you can inform the garbage collector to bypass the finalization process by calling GC.SuppressFinalize(). If the object user forgets to call Dispose(), the object will eventually be finalized and have a chance to free up the internal resources. The good news is that the object s internal unmanaged resources will be freed one way or another. Here is the next iteration of MyResourceWrapper, which is now finalizable and disposable, defined in a C# Console Application named FinalizableDisposableClass: // A sophisticated resource wrapper. public class MyResourceWrapper : IDisposable { // The garbage collector will call this method if the // object user forgets to call Dispose(). ~MyResourceWrapper() { // Clean up any internal unmanaged resources. // Do **not** call Dispose() on any managed objects. } // The object user will call this method to clean up // resources ASAP. public void Dispose() { // Clean up unmanaged resources here. // Call Dispose() on other contained disposable objects. // No need to finalize if user called Dispose(), // so suppress finalization. GC.SuppressFinalize(this); } } Notice that this Dispose() method has been updated to call GC.SuppressFinalize(), which informs the CLR that it is no longer necessary to call the destructor when this object is garbage-collected, given that the unmanaged resources have already been freed via the Dispose() logic.

Summary

In the real world, an end user has the option of supplying command-line arguments when starting a program. However, during the development cycle, you may wish to specify possible command-line flags for testing purposes. To do so with Visual Studio 2010, double-click the Properties icon from Solution Explorer and select the Debug tab on the left side. From there, specify values using the command-line arguments text box (see Figure 3-3).

Figure 3-3. Setting command arguments via Visual Studio 2010 Once you have established such command-line arguments, they will automatically be passed to the Main() method when debugging or running your application within the Visual Studio IDE.

After reading this chapter, you should understand in general how Drupal works and have an overview of what happens when Drupal serves a request. The components that make up the web page serving process will be covered in detail in later chapters.