Silverlight Interview Questions and Answers (58)

No, Silverlight project doesn't support normal ADO.NET objects like DataTable, DataSet, DataColumn, Database connection providers like SqlConnection, OledbConnection objects.

You can use System.Data namespace but that contains Services related stuffs not ADO.NET stuffs.

Styles elements are supported in the form of application resources. An app.xaml file can be created containing an application resource Xml construct. The target type for each style is set to the control on which the style needs to be applied.

App.xaml:
<Application.Resource>
<Style x:Key="MyBorder" TargetType="Border">
<setter property="width" value="5">
</style>

Page.xaml:
<Border Style="{StaticResource MyBorder}">
...
</Border>

Canvas Panel:

use a canvas for simple layouts and when there is no need to resize panel. Controls can overlapped each other when resizing the panel.

Stack Panel:

use this for grouping controls in a stack (horizontal/vertical). Controls do not overlapped.

Grid Panel:

most flexible, multi row/columns layouts. Similar to a HTML table

Generally you can't set the UserControl width in % like 100% so that the Silverlight contents can spread in the full screen.

To get the 100% width of the screen you can set width="auto" and height="auto".

To design the layout of the Silverlight application, XAML language is used.

Extensible Application Markup Language (XAML, pronounced zammel ['zæm??]) is a declarative XML-based language created by Microsoft which is used as a user interface markup language to define UI elements, data binding, eventing, and other features.

We can either use Visual C# or Visual Basic to code the backend of the silverlight application. Here backend means the code behind files for the Sivlerlight pages.

When we create a Silverlight application from Visual Studio, two (2) xaml files are created into the Silverlight project.

They are:
1. App.xaml - App.xaml is a file used to declare shared resources like brushes, various style objects etc. and to handle the global application level event (this is almost similar to global.asax file in asp.net application). By default following events are created in the App.xaml.cs file.

Application_Startup
Application_Exit
Application_UnhandledException
ReportErrorToDOM

2. MainPage.xaml or Page.xaml - This page is the default page of the Silverlight application and when the silverlight application runs this becomes the default page to appear (this page is like the default.aspx page of asp.net application)

To change the default page of Silverlight application, you need to set the RootVisual property inside the Application_Startup even of App.xaml file.

private void Application_Startup(object sender, StartupEventArgs e)

        {

            this.RootVisual = new YourPage();

        }

UserControl is the parent xaml tag of the Silverlight page. All other tags are placed under UserControl tag.

<UserControl x:Class="SilverlightApplication2.MainPage"

    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 

    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 

    Width="400" Height="300">

    <Grid x:Name="LayoutRoot" Background="White">



    </Grid>

</UserControl>

ClientBin folder is used to place the .xap file of Silverlight application. You can keep this anywhere in your web application but this is the default that is used by the Silverlight.

Following is a very good FAQ about the .xap posted on asp.net page.

What does XAP mean?
XAP (pronounced ZAP) is the file extension for a Silverlight-based application package (.xap). This file contains the compressed assemblies and resources of a Silverlight 2 application.

What is a .xap file?
A .xap file is a Silverlight-based application package (.xap) that is generated when the Silverlight project is built.

Why is XAP important?
Tools, such as Visual Studio 2008 with the Microsoft Silverlight Tools Beta 2 for Visual Studio 2008, allow you to create Silverlight applications that are heavily client based using managed code. You can use managed code, such as C# or Visual Basic, and benefit by using the tools that you are used to working with.

How does XAP work?
Once you have created the .xap file (explained below), the Silverlight 2 plug-in downloads the file and runs it in a separate work space.

How do I use a .xap file?
A .xap file is used to contain and transfer the assemblies and resources of a managed code application. This managed code application must be run within the Silverlight 2 browser plug-in.

Visit http://forums.asp.net/t/1277554.aspx for complete details.

Silverlight.js is a helper file which enables Web sites to create advanced Silverlight installation and instantiation experiences.

For more details visit http://code.msdn.microsoft.com/silverlightjs

No, You can't add the reference of a Class library inside the Silverlight application project. You can only add the reference of another Silverlight application project inside a Silverlight application project.

However, you can add the reference of a Web Service or WCF services.

Silverlight 1.0 uses JavaScript, while Silverlight 2.0 uses C# (managed code) for event handling. We will be describing the event model for Silverlight 2.0.

The event handlers are defined in the code-behind file that backs the XAML definition of your User Interface (UI), namely mypage.xaml.cs.

The Silverlight Event Mode

In Silverlight, there are two event cases:


Input events
Non-input events.

Input Events: The browser that hosts the Silverlight plug-in handles initial input stimulus for the input events. This is because Silverlight works within the plug-in architecture of the hosting browser. From the browser, the event is sent to the Silverlight plug-in.

Then, it is raised as an event in the Silverlight Object Model.


Non-input Events: They report a state change to a particular object, for example, the state change events that report asynchronous download state or progress of actions initiated by Web Client. Some non-input events provide lifetime information of objects at a framework level.

For example the FrameworkElement.Loaded event


Some events, such as OnError, can only be handled by the Silverlight plug-in instance and exist within the HTML Document Object Model (DOM). These events need to be continually exposed and possibly handled by any script working with the plug-in instance in the DOM. Therefore; these events are not passed to the managed programming model.