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On demand assembly loading in silverlight

In this article I will explain how to load assembly on demand in Silverlight. This topic contains following sections

   1. Software Requirement

   2. Prerequisite Knowledge

   3. What is on demand assembly loading?

   4. Steps of implementation

   5. Create a new Silverlight project

   6. Add Silverlight class library project in the solution

   7. Add a Silverlight user control in the library project

   8. Add code in Silverlight user control

   9. Set the output path of library project

   10. Add a reference of library project in Silverlight application

   11. Add code in Silverlight application

   12. Output

Software Requirement

Before you start reading this tutorial you should make sure

   1. Visual studio 2008 (or above) is installed on your machine.

   2. Silverlight (4 or 5) runtime is installed on your machine.

   3. Silverlight plug in for browser.

Prerequisite Knowledge

Before you go ahead, it is required that you should know

   1. Basic knowledge of programming in C#.

   2. Basic knowledge of programming in Silverlight.

   3. How to create .net projects(Silverlight as well as non Silverlight)

What is on demand assembly loading?

In the real time scenario if we use a third party component then first of all the whole screen including the component gets loaded

Steps of implementation

Following steps will be followed

   1. Create a new Silverlight application.

   2. Add a custom control project in the solution.

   3. Set the output path of custom control project.

   4. Add reference of custom control project in Silverlight application.

   5. Use WebClient class to load the control at run time.

Let us execute each step one by one.

Create a new Silverlight project

First of all create a project of type ‘Silverlight Application’. See the screen shot below for project structure.

Click to Enlarge

Add Silverlight class library project in the solution

For adding new project, right click on the solution and add a new project of type ‘Silverlight class library’. See the screen shot below for project structure.

Click to Enlarge

Add a Silverlight user control in the library project

Add a new file of type ‘Silverlight user control’ in the custom library project. See the screen shot below for project structure.

Click to Enlarge

Add code in Silverlight user control

Add following control in ‘LoadOnDemandCustomControl.xaml’

xaml

<Grid x:Name="LayoutRoot" >
        <Border BorderThickness="5" CornerRadius="12" Width="500" Height="200" BorderBrush="DarkRed"  Background="BurlyWood" >
            <StackPanel Orientation="Vertical" >
                <TextBlock Text="Feedback Form"></TextBlock>
                <TextBlock Text="Date :" x:Name="txtLoaded"></TextBlock>
                <TextBlock Text="Enter Your Feedback Please" x:Name="lblFeedback"></TextBlock>
                <TextBox x:Name="txtFeedback" Width="Auto" Height="Auto" TextWrapping="Wrap"></TextBox>
                <Button Content="Submit" Height="23" Name="btnSubmit" Width="75" />
            </StackPanel>
        </Border>
</Grid>

Code behind

public LoadOnDemandCustomControl()
{
    InitializeComponent();
    this.Loaded += new RoutedEventHandler(LoadOnDemandCustomControl_Loaded);
}
void LoadOnDemandCustomControl_Loaded(object sender, RoutedEventArgs e)
{
     txtLoaded.Text += DateTime.Now.ToString();
}

Set the output path of library project

To set the output path

1. Right click on the project and click properties.

2. Property tab appears. In the ‘Build’ tab set the output path to the ‘ClientBin’ folder of the web application

Click to Enlarge

Add a reference of library project in Silverlight application

Add a reference of library project i.e. ‘OnDemand’ to the Silverlight application

Click to Enlarge

Add code in Silverlight application

Add the following code in ‘MainPage.xaml’

Xaml

<Grid x:Name="LayoutRoot">
        <StackPanel x:Name="stkControls" Orientation="Vertical" Width="Auto" HorizontalAlignment="Center" VerticalAlignment="Center" >
            <Button Content="Click here for feedback" x:Name="btnLoad" Click="btnLoad_Click"></Button>
        </StackPanel>
</Grid>

Code behind

private bool customControlsLoaded = false;

private void btnLoad_Click(object sender, RoutedEventArgs e)
{
            if (!customControlsLoaded)
            {
                WebClient wc = new WebClient();
                wc.OpenReadCompleted += new OpenReadCompletedEventHandler(wc_OpenReadCompleted);
                wc.OpenReadAsync(new Uri("OnDemand.dll", UriKind.Relative));
            }
            else
                AddCustomControl();
}

void wc_OpenReadCompleted(object sender, OpenReadCompletedEventArgs e)
{
            if (e.Error == null && e.Result != null)
            {
                AssemblyPart part = new AssemblyPart();
                part.Load(e.Result);
                customControlsLoaded = true;
                AddCustomControl();
            }
}

private void AddCustomControl()
{
            OnDemand.LoadOnDemandCustomControl ctrl = new OnDemand.LoadOnDemandCustomControl();
            stkControls.Children.Add(ctrl);
            this.btnLoad.Visibility = System.Windows.Visibility.Collapsed;
}

In the code I am calling dll at run time using WebClient class.

Output

Click to Enlarge

Now, click on ‘Click here for feedback’ button. You will get below output.

Click to Enlarge

Posted By -	Ritesh Arya

Posted On -	Monday, September 3, 2012

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