Handling Null values returned by the Bound object.
Using the ‘TargetNullValue=Value’ as an additional parameter in the Binding statement {} you can catch instances where the returned data is null and in its place use the specified value.
Example: <TextBlock x:Name="HandleNullsExample" Text="{Binding Cost, TargetNullValue=None}”>
Formatting Money/Currency
Using the ‘StringFormat=C’ as an additional parameter in the Binding statement {} you can format the returned data as a currency.
Example: <TextBlock x:Name="CurrencyExample" Text="{Binding Cost, StringFormat=C}”>
Formatting Dates
Using ‘StringFormat=MM/dd/yyyy’ as an additional parameter in the Binding statement {} you can format the returned data as a date.
Example: <TextBlock x:Name="BirthDateValueTextBlock" Text="{Binding BirthDate, StringFormat=MM/dd/yyyy}”>
Fallback Values when Binding fails
Using ‘FallbackValue=Value’ as an additional parameter in the Binding statement {} you can pass in a value that will be used when the data binding fails.
Example: <TextBlock x:Name="ManagerOfValueTextBlock" Text="{Binding ManagerOf, FallbackValue=NA}”>

To pass initialization parameters (InitParams) to your Silverlight application at its startup you can simply add a new  ‘initParams’ element to the Silverlight Object markup within your page. The ‘initParams’ element contains for its value a hash of key value pairs you wish to pass into the application in the for “key=value”.
Example:

<object data="data:application/x-silverlight-2," type="application/x-silverlight-2" width="100%" height="100%">
    <param name="source" value="ClientBin/JoxStrap.Silverlight.Home.xap"/>
    <param name="onError" value="onSilverlightError" />
    <param name="background" value="white" />
    <param name="minRuntimeVersion" value="3.0.40624.0" />
    <param name="autoUpgrade" value="true" />
    <param name="initParams" value="baseUri=http://local.joxstrap.com" />
    <a href="http://go.microsoft.com/fwlink/?LinkID=149156&v=3.0.40624.0" style="text-decoration:none">
      <img src="http://go.microsoft.com/fwlink/?LinkId=108181" alt="Get Microsoft Silverlight" style="border-style:none"/>
    </a>
     </object><iframe id="_sl_historyFrame" style="visibility:hidden;height:0px;width:0px;border:0px"></iframe></div>
After adding the ‘initParam’ element to the object markup you then read in these parameters in the Application_Startup method located in your App.xaml.cs file. 

private void Application_Startup(object sender, StartupEventArgs e)
        {
            StartUpParameters startup = StartUpParameters.Instance;

            try
            {
                string uriString = e.InitParams["baseUri"];
                if (!string.IsNullOrEmpty(uriString))
                {
                    Uri baseUri = new Uri(uriString);
                    startup.BaseUri = baseUri;
                }
            }
            catch
            {
                startup.BaseUri = null;
            }

            RootVisual = new MainPage();
        }
	

If when you hover over the dropdown menus in your website and find that they are disappearing behind your Silverlight media elements in the page making it impossible to click on the hidden menu items, there is a simple solution. You need to activate the ‘windowless’ mode for all Silverlight media elements which are within reach of your dropdowns.
To do this just add the following parameter to your object markup for the Silverlight element.

<param name="windowless" value="true"/>
Your object markup should now look something like this:

 <object data="data:application/x-silverlight-2," type="application/x-silverlight-2"
            width="950px" height="665px">
            <param name="windowless" value="true"/>
            <param name="source" value="URI_TO_SILVERLIGHT_FILE" />
            <param name="onError" value="onSilverlightError" />
            <param name="minRuntimeVersion" value="3.0.40624.0" />
            <param name="autoUpgrade" value="true" />
            <a href="http://go.microsoft.com/fwlink/?LinkID=149156&v=3.0.40624.0" style="text-decoration: none">
                <img src="http://go.microsoft.com/fwlink/?LinkId=108181" alt="Get Microsoft Silverlight"
                    style="border-style: none" />
            </a>
        </object>
        <iframe id="_sl_historyFrame" style="visibility: hidden; height: 0px; width: 0px; border: 0px"></iframe>
	

With the addition of Behaviors in Silverlight 3 we have the opportunity to reduce a lot of the code we write in order to create interactivity within our application. Expressions Blend 3 comes with several built-in behaviors right at your fingertips. You can find them in the Assets panel (left side) under the Behaviors group.

• ChangePropertyAction
• ControlStoryboardAction
• FluidMoveBehavior
• GoToStateAction
• HyperlinkAction
• MouseDragElementBehavior
• PlaySoundAction
• RemoveElementAction

In this example we will be building a simplistic sound playing app using the ChangePropertyAction as well as the PlaySoundAction Behaviors. By utilizing these 2 built-in Behaviors we can completely eliminate writing a single line of code.