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

he first three chapters of this book gave you an overview of Ajax and Atlas and how you can use them to build web applications using this technology to restrict unnecessary postbacks and processing on your web pages, thus improving the performance and polish of your web applications. s 4 and 5 introduced you to the client-side controls presented by Atlas and stepped you through many examples of how to use these controls in JavaScript and in a new XML-based script called Atlas Script. You looked at some advanced aspects of the scripting framework, including actions, which are compound commands associated with an event or stimulus on a control; behaviors, which are automatic units of functionality that can be associated with a control, enabling things such as drag and drop; and data binding, which allows for controls to be wired up to each other or to themselves in order to pass data between them. In this chapter, you will go to the other side of the action the server and begin exploring the various server-side controls available to you when building your Atlas applications. You have seen one of these controls, the ScriptManager control, already. In this chapter you will look at ScriptManager in more detail. In 7, you will start learning about how these controls work by navigating through some examples.

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As far as users of the Plane class are concerned, there s no discernible difference between the two approaches the way in which properties work is an encapsulated implementation detail. Example 3-11 shows an updated Main function that uses the new properties. It neither knows nor cares which one is the real one.

To try out the signals and slots in MyClass, the a, b, and c instances are created: QObject parent; MyClass *a, *b, *c; a = new MyClass( "foo", &parent ); b = new MyClass( "bar", &parent ); c = new MyClass( "baz", &parent ); Now connect them. To connect signals and slots, the QObject::connect method is used. The arguments are source object, SIGNAL(source signal), destination object, SLOT(destination slot). The macros SIGNAL and SLOT are required; otherwise, Qt refuses to establish the connection. The source and destination objects are pointers to QObjects or objects of classes inheriting QObject. The source signal and destination slot are the name and argument types of the signal and slot involved. The following shows how it looks in the code. Figure 1-3 shows how the object instances are connected. QObject::connect( a, SIGNAL(textChanged(const QString&)), b, SLOT(setText(const QString&)) ); QObject::connect( b, SIGNAL(textChanged(const QString&)), c, SLOT(setText(const QString&)) ); QObject::connect( c, SIGNAL(textChanged(const QString&)), b, SLOT(setText(const QString&)) );

static void Main(string[] args) { Plane someBoeing777 = new Plane("BA0049"); someBoeing777.SpeedInMilesPerHour = 150.0; Console.WriteLine( "Your plane has identifier {0}, " + "and is traveling at {1:0.00}mph [{2:0.00}kph]", someBoeing777.Identifier, someBoeing777.SpeedInMilesPerHour, someBoeing777.SpeedInKilometersPerHour); someBoeing777.SpeedInKilometersPerHour = 140.0; Console.WriteLine( "Your plane has identifier {0}, " + "and is traveling at {1:0.00}mph [{2:0.00}kph]", someBoeing777.Identifier, someBoeing777.SpeedInMilesPerHour, someBoeing777.SpeedInKilometersPerHour); } Console.ReadKey();

Although our public API supports two different units for speed while successfully keeping the implementation for that private, there s something unsatisfactory about that implementation. Our conversion relies on a magic number (1.609344) that appears repeatedly. Repetition impedes readability, and is prone to typos (I know that for a fact. I ve typed it incorrectly once already this morning while preparing the example!) There s an important principle in programming: don t repeat yourself (or dry, as it s sometimes abbreviated). Your code should aim to express any single fact or concept no more than once, because that way, you only need to get it right once. It would be much better to put this conversion factor in one place, give it a name, and refer to it by that instead. We can do that by declaring a field.

Notice how it includes the extra characters we included (the - and the but).

Caution Trying to specify signal or slot argument values when connecting will cause your code to fail at

Were you expecting the output to be 123-456 but 78 The framework applies the placeholder rule for the lefthand side of the decimal point, so it drops the first nonrequired placeholder, not the last one. Remember that this is a numeric conversion, not something like a telephone-number format. The behavior may be easier to understand if you replace each # with 0. In that case, we d get 012-345 but 678. Using # just loses the leading zero.

If you want to include one of the special formatting characters, you can do so by escaping it with a backslash. Don t forget that the C# compiler will attempt to interpret backslash as an escape character in a literal string, but in this case, we don t want that we want to include a backslash in the string that we pass to ToString. So unless you are using the @ symbol as a literal string prefix, you ll need to escape the escape character as Example 10-28 shows.

int value = 12345678; string text = value.ToString("###-### \\# ###"); Console.WriteLine(text);