INTERFACES in Visual C#

Printer Denso QR Bar Code in Visual C# INTERFACES

You can also define and implement interfaces with the Microsoft AJAX Library. These interfaces are again similar to those in the .NET Framework; they represent contracts that the class must implement. You can also implement multiple interfaces in a class. You indicate that a class should implement an interface by using the registerClass method. This was shown earlier and is repeated in the following code. The third parameter of this method represents the interfaceTypes that the class implements. You can pass a single interface (as shown here with Sys.IDisposable) or multiple interfaces.

Contoso.Utilities.ChangePasswordValidator.registerClass( 'Contoso.Utilities.ChangePasswordValidator', null, Sys.IDisposable);

The library also allows you to define and implement your own interfaces. To create an interface, you define it as you would a class. However, you do not add implementation to the interface, you just include method stubs. You then call the registerInterface method of the Type class. This registers your interface for use with the library. The following code shows an example of defining and registering an interface with the library.

//declare an interface Contoso.Utilities.IValidationLogic = function() {} Contoso.Utilities.IValidationLogic.prototype = { get_isValid: function(){}, get_validationRules: function() {}, validate: function(){} } Contoso.Utilities.IValidationLogic.registerInterface( "Contoso.Utilities.IValidationLogic");

When you write JavaScript that is intended to be used by the Microsoft AJAX Library, you need to tell the library when you have finished loading your script. You can do so by calling the notifyScriptLoaded method of the Sys.Application object. The following shows an example.

//indicate that this is the end of the class / script if (typeof(Sys) !== 'undefined') Sys.Application.notifyScriptLoaded();

Classes you create with the Microsoft AJAX Library can be used directly within your ASPX pages. To do so, you must first register the class with the ScriptManager. This tells the ScriptManager you have a class that is built with the library in mind. It also ensures that you get IntelliSense in the IDE for your namespaces, classes, methods, and so on. The following page script shows an example of how you would add the script that was defined in the previous section to the page.

<asp:ScriptManager ID="ScriptManager1" runat="server"> <Scripts> <asp:ScriptReference path="ContosoUtilities.js" /> </Scripts> </asp:ScriptManager>

After the custom classes have been defined, you can use the class library as required in pagelevel script. For example, you can create a new instance of the ChangePasswordValidator control created earlier by using the new keyword and passing in the appropriate parameters to the constructor. The following code shows an example of creating an instance of the class and uses the enumeration, calling properties, and calling methods.

<script language="javascript" type="text/javascript"> //call constructor var validator = new Contoso.Utilities.ChangePasswordValidator(true, true, true); //check the password strength strength = validator.CheckPasswordStrength("password"); switch (strength) { case Contoso.Utilities.PasswordStrength.Weak: alert("Weak"); break; case Contoso.Utilities.PasswordStrength.Medium: alert("Medium"); break; case Contoso.Utilities.PasswordStrength.Strong: alert("Strong"); break; }

//set properties validator.set_currentPassword("password"); validator.set_changeToPassword("pas2"); //call methods if (validator.AllowPasswordChange()) { alert("Password may be changed"); } else { var violations = validator.get_passwordRuleViolations(); alert("Rule violations: " + violations.length); for (i = 0; i < violations.length; i++) { alert("Rule violation " + i + " = " + violations[i]); } } </script>

The Microsoft AJAX Library also includes a client-based event life cycle. You can use this life cycle to intercept events when the page runs, and load your code as required. Think of this as similar to how you work with code-behind files. For example, in a code-behind file you might write code in the Page_Load event. Similarly, in the code you write to run in the browser, you can implement the Sys.Application.load event. Fortunately, the life cycle of your client code is very similar to that of your server code. This includes events for init, load, unload, and disposing. In this way, the Application client object works in a similar way as the Page object in your server code. To take advantage of this event model you must, of course, use a ScriptManager control on your page. You register an event in script by using the add_event syntax. The following code shows how you would register code with the Sys.Application.Load event.

Sys.Application.add_load(PageLoad); function PageLoad(sender) { //page-load code goes here }

The library also allows you to unregister (or remove) events. You do so in a similar manner, by using the remove_<event name> syntax. The following shows an example.

Sys.Application.remove_load(PageLoad);