Q1. What is Silverlight?
-
Silverlight is a powerful technology used to build rich browser,
desktop and mobile user experience (UX) applications with the support
for Media, multithreading, data binding, 2-D and 3-D graphics. Powered
by the .NET framework, Silveright is a free plug-in and compatible with
multiple browsers, devices and operating systems
- It has its own CLR (coreclr.dll) and exists as a browser plug-In (npctrl.dll).
- For Silverlight development, you can either install Silverlight using the Web Platform Installer or use Silverlight 4 Tools for Visual Studio 2010.
- The latest version is Silverlight 4.0 and a plan has been laid out for Silverlight 5.0
Q2. Is Silverlight a replacement for ASP.NET?
Absolutely
not. ASP.NET provides its own power of server side programming, with
more enhanced security. Silverlight plugin executes inside the browser
sandbox (client side) and needs to be configured explicitly for security
using WCF services for authorization and authentication. A mix of
ASP.NET and Silverlight is used in most applications.
Q3. Can we develop Client-server applications or Intranet applications using Silverlight?
This
totally depends on the architecture and application requirements. One
important thing to note here is that Silverlight applications cannot
‘directly’ connect to the database server. So thinking of a
client-server application development using Silverlight might require
some thinking on your part. WindowsForm or WPF can be a good choice
in this scenario.
Q4. What type of applications can be developed using Silverlight?
You
can think of developing browser or mobile applications using
Silverlight, where you need to represent output in a graphical form, a
rich UX. For E.g. In case of a healthcare application, you can think of
using Silverlight for simulating ECG of the patient, as shown below:
The above output
makes use of Polyline 2-D graphical element of Silverlight. Likewise
various types of Line-of-Business (LOB) applications, for various
domains can be developed. Some example are :
- Healthcare.
- Insurance
- Logistic
and any other domains you can think of.
Q5. How then the data be made available to Silverlight applications?
-
For developing Line-Of-Business (LOB) applications, Silverlight
supports Data-Binding features with OneWay, TwoWay binding mechanism.
- Using Windows Communication Foundation (WCF), data from the remote server can be made available to Silverlight applications.
-
The communication between Silverlight and WCF service is possible using
‘basicHttpBinding’. This is the binding provided in WCF service for
HTTP protocol with plain text communication from Silverlight to WCF.
Q6. What types of security measures are provided with Silverlight?
- For secure communication, Silverlight makes use of WCF service and uses the security features of WCF.
- You can also make use of Secure Socket Layer (SSL) transport security mechanism from Silverlight to WCF.
Q7. Can the Silverlight application be deployed on the desktop?
-
Yes, Absolutely possible. With Silverlight 3.0 version and onwards, the
Out-Of-Browser (OOB) facility has been provided. Using this feature,
the Silverlight application can be physically deployed on local machine.
- In Silverlight 4.0 the OOB facility has been enhanced with
elevated rights, which allows a Silverlight application to do the
following:
-Communicate with Word, Excel type applications by using COM enhancements, provided in Silverlight 4.0.
-Communicate with local database e.g. MS-Access, Sql Server etc.
Q8. Where is the Silverlight application present, is it on the Web server or on the Client?
-
The Silverlight application in most cases is hosted in an ASP.NET
webpage, although it can be hosted on HTML pages too. The extension of
the SL plugin is .xap.
- When the end-user makes an HTTP request to
this ASP.NET page (.aspx), the Silverlight application is made available
to the browser and the result is displayed.
Q9. What are the controls provided in Silverlight for Line-of-Business (LOB) applications?
You can make use of following controls:
- DataGrid.
- DataForm.
- Chart controls etc.
Q10. Can the Silverlight application communicate with ASP.NET?
This can be possible using:
- Cookies.
- QueryString.
- You can use JavaScript on the ASP.NET page and it can be called in Silverlight.
Q11. What is the real advantage of using Excel/Word files or local database in Silverlight?
-
This can be required when the end-user is using Silverlight application
in OOB (Out-Of-Browser) and for storing and fetching the frequently
required data, instead of relying on WCF service for data communication,
the data can be fetched and stored in Excel sheet on the local database
- In case of the Excel/Word files communication, they are recommended to be stored in ‘MyDocuments’ special folder.
Q12.What are the advantages of Extensible Application Markup Language (XAML) over C# or VB.NET
- One important thing note here is that C#/VB.NET (code-behind files) have their own important roles to play.
-
XAML provides lots of features like code-less development, creating
complex UI controls E.g. creating image list by using ListBox and Image
control used together.
- The XAML file can define an instance of the
class created using C# and VB.NET and all public properties declared in
this class can be directly bound in XAML elements.
Q13. Can we use any specific Patterns in Silverlight programming?
-
Yes. In Silverlight, Model-View-View-Model (MVVM) can be used for
loosely coupled application development where code can be completed
isolated from the XAML.
- We can also use Prism in Silverlight which is a set of classes provided for developing next generation loosely coupled, flexible LOB applications.
What is XAP file?
XAP
(pronounced as ZAP) is the compressed output of the Silverlight
Application which includes application manifest file, compiled output
assembly and other resources used by your silverlight application. This
uses the normal ZIP compression method to reduce the total download
size. When you build your Silverlight application, it actually generates
this .XAP file & puts in the output folder which the .aspx page
refers as source to load the application.
Once you build
your project, it will create the XAP file (in our case:
SilverlightApps.HelloSilverlight.xap) and put it into the ClientBin
directory of the web project. When the page loads it will pickup from
the same location as the source you specified inside the aspx/html page.
What is MainPage.xaml file?
When you create the Silverlight
project, Visual Studio IDE will automatically add a default
“MainPage.xaml” file which is actually a startpage for your Silverlight
application. You can modify this page as per your need or can create a
new one. So, what’s there inside the file? Lets look at it:
Lets
walk-through each lines of the code. It contains a UserControl as root
of the file which may contain all other controls inside it. The
following line tells the compiler to use the specified class to use:
The
next couple of lines beginning with xmlns tells the compiler to import
some namespaces which can be used by the Silverlight XAML page.
The following line speaks about the design time Height & Width of the Silverlight page:
If
you want to specify actual Height & Width of your Silverlight
application, you can manually append the following line inside that:
Next
comes the Grid control which is used as a layout panel and that can
include more other controls. Though the default XAML file uses the Grid
as the layout panel, you can change it to any other panel as per your
need. I will discuss about the various panel later in this tutorial.
“MainPage.xaml”
has also it’s code behind file like App.xaml & you can use this to
write code to develop your functionalities. By default, it comes empty
with a call to Initialize() method inside the Constructor of the
MainPage class. The implementation of this method is also available in a
different partial class of MainPage inside “MainPage.g.i.cs” like “App”
class. Whenever you add some controls inside the XAML page, it will be
loaded here.
How can I host a Silverlight Application?
When
you create a Silverlight project, it asks you to create a Web
Application project. This project is responsible for hosting your XAP
file. Generally Silverlight application doesn’t require any server to
host it to run, but if you are planning to host it in web you must need a
web server for that.
Once you publish your Web Application to
host in IIS, you may need to add three MIME types in your IIS Server.
This is require to host it in earlier versions of IIS. Latest version of
IIS comes with that configuration by default. Followings are the list
of MIME Types those you need to add in your IIS Properties:
.xap application/x-silverlight-app
.xaml application/xaml+xml
.xbap application/x-ms-xbap
Silverlight
Application (XAP) generally loads inside the ASPX or HTML pages
pointing to the path to load the XAP. The aspx/html page uses <object
/> tag to load the Silverlight application.
Here is the code present inside the aspx/html pages for loading the Silverlight XAP:
Let us go line by line to learn the basics of it.
- In the first line <object> tag tells the browser to load the Silverlight plug-in.
- Next couple of lines uses <param> tag.
- The first param “source” has the value to the location of the .xap file.
- Second param “onError” tells the plug-in to call the javascript method mentioned in the value, if any application error occurs.
- The third param “background” specifies the color of the Silverlight application background.
- The next param “minRuntimeVersion” specifies the minimum required plug-in version to load your Silverlight application.
- If “autoUpgrade” is set as true in the next param, it will automatically upgrade the runtime.
- The
next lines are very interesting. Whatever you design there, will not be
visible in the browser in normal scenarios. If the user doesn’t have
Silverlight runtime installed in his PC or the Silverlight plug-in is
disabled this section will visible to the user. This part is well known
as “Silverlight Installation Experience panel”. By default, it shows a
Silverlight image to download the runtime from Microsoft site. When the
user clicks on it, this starts the installation. I will discuss about
the Silverlight Experience later in depth.
What is XAML?
XAML stands for eXtended Application Markup
Language. It is nothing but an XML file which is used to declaratively
create the User Interface of the Silverlight or WPF applications. This
XAML file generally rendered by the Silverlight plugin and displayed
inside the browser window. When you compile your projects which includes
XAML pages, those first converts into BAML (Binary Application Markup
Language) and then rendered in the web browser window. Let use see a
simple example of XAML here:
The
above XAML is a typical example where I am creating a text using the
TextBlock control by specifying different properties as attributes to
the control for name, font-family, weight, text etc.
What is Silverlight?
Silverlight is a powerful cross-browser
& cross-platform technology for building the next generation web
experience & rich internet applications for the web. You can run
Silverlight in most of all the popular browsers like Internet Explorer,
Firefox, Chrome, Safari etc. Silverlight can run in various devices and
operating systems like Windows, Apple Mac OS-X and Windows Phone 7.
Using Silverlight you can create rich, visually stunning web
applications like flash. Also you can create smooth animations using
Storyboards; you can stream media over the net etc.
Silverlight
web browser plug-in comes as free to install (approximately 4-5 MB in
size). You can download the required plug-in from Microsoft Silverlight
Site.
What is App.xaml file?
App.xaml file is the loader of your
Silverlight Application. You can declare your shared/global resources,
styles, templates, different brushes inside this file which will be
accessible by your application.
A typical App.xaml file looks like:
It
has a code behind file too named as “App.xaml.cs”. This file is used to
handle global application level events which you can use as per your
need. Visual Studio creates these two files at the time of project
creation. The three events inside the App.xaml.cs are:
- Application_Startup
- Application_Exit
- Application_UnhandledException.
These three events are registered in the constructor of your App.xaml.cs file. Here is the code snippet of the same:
Let us do a brief discussion on each part of the code file.
Overview of App Constructor: Inside
the constructor of the App class you will find that all the three event
has been registered. Also, there is a call to InitializeComponent()
method. If you look around the whole class you will not find the method
implementation. Strange!!! Where is the method?
The method
has been implemented inside the partial class of the App class. If you
go to the definition or just press F12 on top of the method, Visual
Studio will open up the actual file named “App.g.i.cs” which contains
the partial implementation of the same class. There you will find the
method implementation.
What this method does:
This method is responsible to load the XAML using the LoadComponent()
method into the memory which can be used by your application.
What can we do inside the App.g.i.cs file:
App.g.i.cs file is auto generated by the compiler and hence if you
modify something there will be overwritten by the compiler itself on
next build.
Why this file is not available inside my solution:
As this is an compiler generated file, it has been placed inside the
temporary directory named “obj”. If you go to the solution directory you
will see the “obj” folder. Open it and browse through it’s subfolder
(either debug or release) and you will see the file placed there. If you
are unable to find it there, just do a rebuild of your solution and
immediately it will be created there.
Overview of Application_Startup Event:
Application_Startup
event is the root of your application. In this event you can create the
instance of your initial page and set it as the RootVisual. Also, if
you want to create some global objects or want to write some app
initialization code, then this Application_Startup event will be the
best part for you to implement it.
Overview of Application_Exit Event:
Similarly,
you can write code to cleanup objects or do something when closing the
application inside the Application_Exit event.
Overview of Application_UnhandledException Event:
If
any exception comes while running and you didn’t handle that in the
actual place, you can write some code in Application_UnhandledException
to log the error details into database or show some message to the user.
This will allow the application to continue running after an exception
has been thrown. By default, if the app is running outside of the
debugger then report the exception using the Browser DOM & the error
will be visible in the status bar of Internet Explorer.
What are the Prerequisite to create a new Silverlight Application?
Before starting with the Silverlight application development be sure
you have all the necessary softwares installed in your PC. If you don’t
have then follow the steps mentioned in Microsoft Silverlight Site (
http://silverlight.net/getstarted/) to download & install the following items in your development environment:
- Visual
Studio 2008 SP1 for Silverlight 3 application development or Visual
Studio 2010 for Silverlight 3 & Silverlight 4 application
development
- Silverlight 3 Tools for Visual Studio 2008 SP1 or Silverlight 4 Tools for Visual Studio 2010
- Expression Blend 3 for Silverlight 3 or Expression Blend 4 Preview for Silverlight 4 (optional)
- WCF RIA Services for Silverlight (optional)
- Silverlight 3 Toolkit or Silverlight 4 Toolkit based on your earlier version of Silverlight (optional)
Remember that, Silverlight 3 comes preinstalled with Visual Studio 2010
and hence if you are using Visual Studio 2010, you don’t need to
install the Silverlight 3 Tools for it. Using Visual Studio 2010 you can
develop both Silverlight 3 and Silverlight 4 applications but Visual
Studio 2008 SP1 only supports Silverlight 3.
If you have
proper development environment ready for Silverlight application you can
proceed to the next chapter for creating our first simple Silverlight
project. I am using Visual Studio 2010 RC and Silverlight 4 RC while
writing these applications. Hence, the attached samples will not open in
Visual Studio 2008.
Can Silverlight run in other platforms other than Windows?
Yes, animations made in Silverlight can run in other platforms other
than Windows. In whatever platform you want to run, you just need the
Silverlight plug-in.
