.NET/ASP.NET/C#/VB.NET PDF Document SDK

Both protected internal and internal are much underused access modifiers. They are a very convenient way of hiding away library implementation details from your consumers, and reducing the amount of documentation and surface-area testing you need. I suspect that they are unpopular (as with most hidden by default or secure by default schemes) because they can sometimes get in your way. There are a fair number of implementation details of classes in the .NET Framework that are internal (or private) that people would very much like to access, for example. A common reason for taking something useful and applying the inter nal modifier is that it was not possible to fully document (or understand the full implications of) the hook this would provide into the framework. And rather than open up potential security or reliability problems, they are marked internal until a later date: perhaps much, much later, tending toward never. Although there is an intention to revisit these things, real-world pressures mean that they often remain unchanged. This is another example of the lock down by default strategy which helps improve software quality. That doesn t make it any less irritating when you can t get at the inner workings, though!

generate barcode excel vba, how to install barcode font in excel 2010, free barcode font excel mac, barcode add in for word and excel pour windows, how to make barcode in excel 2003, install barcode font excel 2007, how to create barcodes in excel 2010, barcode add in for word and excel 11.10 free download, barcode activex control for excel free download, formula to create barcode in excel 2010,

Figure 1-5. A standard C++ project is built. When using QMake, all header files are parsed by the meta-object compiler: moc. The moc looks for classes containing the Q_OBJECT macro and generates meta-objects for these classes. The generated meta-objects are then automatically linked into the final application. Figure 1-6 shows how this fits into the build process. QMake makes this completely transparent to you as a developer.

So we ll mark those methods in the base class virtual and protected, as shown in Example 4-10.

protected virtual void TurnOnHose() { Console.WriteLine("The fire is going out."); } protected virtual void TrainHoseOnFire() { Console.WriteLine("Training the hose on the fire."); }

As you can see from Figure 6-15, the only task associated with the UpdatePanel control is to add a ScriptManager control. The UpdatePanel control cannot function without a ScriptManager control on the page. Additionally, the ScriptManager control must be located before any UpdatePanel controls on your page. In other words, as you read your source code from top to bottom, the ScriptManager reference should appear before the UpdatePanel ones. Using the Tasks Assistant will ensure that it is placed correctly. If your ScriptManager control is not present or is incorrectly placed, you will get an error (see Figure 6-16). The UpdatePanel control contains a designer surface where you can place HTML. This code will be the only code updated upon a postback if the ScriptManager control is enabled for partial updates. Consider Figure 6-17, where several text boxes and a button appear on the screen. This application has two text boxes, two labels, and a button outside the UpdatePanel control, and it has a label inside the UpdatePanel designer. The label on the inside is called lblResult. The code behind the button reads as follows: int x = Convert.ToInt16(txt1.Text.ToString()); int y = Convert.ToInt16(txt2.Text.ToString()); int z = x+y; lblResult.Text = z.ToString(); As you can see, the label for the result will get updated to the value of the sum of the values of the text in the text boxes. Because lblResult is in the UpdatePanel control and the ScriptManager control is set to enable partial rendering, clicking the button will update only the text within the UpdatePanel control. You will see and dissect more examples of this in 7.

We can now create our TraineeFirefighter class (see Example 4-11).

class TraineeFirefighter : Firefighter { private bool hoseTrainedOnFire; protected override void TurnOnHose() { if (hoseTrainedOnFire) { Console.WriteLine("The fire is going out."); }

Remember that Qt is simply standard C++ mixed with some macros and the moc code generator. If Tip

else { } }

Console.WriteLine("There's water going everywhere!");

}

you get compiler or linker messages complaining about missing functions with names telling you that they are signals, the code for the signals is not being generated. The most common reason is that the class does not contain the Q_OBJECT macro. It is also possible to get strange compilation errors by not inheriting QObject (directly or indirectly) and still use the Q_OBJECT macro, or by forgetting to run qmake after having inserted or removed the macro in a class.

protected override void TrainHoseOnFire() { hoseTrainedOnFire = true; Console.WriteLine("Training the hose on the fire."); }

As you can see, the trainee is derived from Firefighter. We added an extra Boolean field to keep track of whether the trainee has actually trained the hose on the fire, and then provided our own implementations of TrainHoseOnFire and TurnOnHose that make use of that extra field. This is intended to model the detailed but slightly peculiar and occasionally erratic way in which the trainee follows the instructions for these operations in his copy of How to Be a Firefighter, rather than allowing common sense to prevail. We also need a quick update to our main function to use our trainee. Let s add the following code at the end: