Kevin Williams .NET and Stuff : Silverlight

Streaming Video - Silverlight, Sitecore, and Windows Media Services

Kevin — Thu, 04 Mar 2010 23:51:00 GMT

For quite a while now, I’ve been wanting a simple video streaming solution that I could recommend to clients for whom progressive video downloads won’t cut it and who don’t want to pay to use a CDN like Edgecast or UVault or Limelight. Clients who don’t need to serve a ton of video on their site, and would be able to host it themselves if it were easy and integrated with their WebCMS.

I’ve started working on just such a solution. Right now, I’m using Windows Media Services 2008 (an optional component of Windows 2008 Server - Standard and Enterprise editions) to host and stream the videos, Sitecore to manage uploading and publishing of new videos and related content, and a Silverlight video player I found called Minoplayer. This requires that videos be encoded to WMV format, but I’m already thinking about ways to support Flash video for people who don’t want to use Silverlight (lighttpd’s mod_flv_streaming module looks promising). And of course, HTML5’s <video> element looks interesting too (although codec support problems may make it more difficult to implement).

You can see an early example of the end result of my work here - http://www.kevinwilliams.name:8001/Kologarn.aspx

(be kind to my server - I’m asking a lot from it running Sitecore, SQL Server, Media Services, and a bunch of other stuff on crappy old hardware)

I will post details of my Media Services installation and configuration experience, some information about the Sitecore solution, etc in the next few days.

Using WebService Data With Silverlight

Kevin — Mon, 24 Mar 2008 04:58:00 GMT

Now, I want to do something a bit more dynamic. How about we call a web service, get some dynamic data back, and render something based on that data? In this post, I will build a simple example in order to clearly illustrate the concepts. But at the end, I will post an example of something a bit more useful to show what can be done!

First off, let's define a simple web service. I used VS2008's New Item wizard and selected "Web Service" from the dialog. Then, I replaced HelloWorld() with my own GetData() method. Here's what the code behind for MyService.asmx looks like:

[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
[ToolboxItem(false)]
// To allow this Web Service to be called from script, using ASP.NET AJAX, uncomment the following line. 
[System.Web.Script.Services.ScriptService]
public class MyService : System.Web.Services.WebService
{
    [WebMethod]
    [ScriptMethod]
    public string[] GetData()
    {
        string[] data = new[] { "first data", "second data", "third data" };
        return data;
    }
}

Note I also have uncommented the ScriptService attribute on my class and added a ScriptMethod attribute to my method. Calling web services from Javascript is a whole lot easier using ASP.NET AJAX. You'll need to have the ASP.NET AJAX 1.0 Extensions installed for this to work, but it's worth it. Oh, I'm also using the new array initialization syntax from C# 3.0 in case you've never seen it before. A real world application would probably query a database or something.

In order to call the web service from Javascript, ASP.NET AJAX requires us to place a ScriptManager on the page with a ServiceReference pointing to the .asmx. Here's what mine looks like:

<asp:ScriptManager ID="ScriptManager1" runat="server">
    <Services>
        <asp:ServiceReference Path="~/MyService.asmx" />
    </Services>
</asp:ScriptManager>

Thankfully, VS2008's web application project template already set up my web.config to use ASP.NET AJAX. If you are not using VS2008, you may need to follow the directions at http://asp.net/AJAX/Documentation/Live/ConfiguringASPNETAJAX.aspx to ensure your web.config is set up properly.

At this point, I can call my web service from Javascript and react to whatever data comes back. The question is - what should it do? For this post, I think I'll just put up a Silverlight TextBlock and rotate through the web service data when the user clicks on the text. Here's the XAML:

<Canvas xmlns="http://schemas.microsoft.com/client/2007" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
 
    <TextBlock x:Name="MyTextBlock" FontSize="10" FontFamily="Arial" Canvas.Top="10" Canvas.Left="10" Loaded="MyTextBlockLoaded" MouseLeftButtonDown="MyTextBlockClick" />
 
</Canvas>

First, I will retrieve the data from the web service once the text block has loaded by using the Loaded event. Let me show you the Javascript and then I will explain it...

var index;
var data;
 
function MyTextBlockLoaded( sender, args )
{
    MyService.GetData( GetDataSuccess, GetDataFailed );
}
 
function GetDataSuccess( result )
{
    data = result;
    index = 0;
    UpdateTextBlock();
}
 
function GetDataFailed()
{
    alert( 'Call to MyService.GetData() failed!' );
}
 
function UpdateTextBlock()
{
    var textblock = document.getElementById( '<%= Silverlight1.ControlId %>' ).content.findName( 'MyTextBlock' );
    textblock.Text = data[index];
}

First I declare a variable to hold the current index into the data array and a variable to hold the data itself. The implementation of the MyTextBlockLoaded() event handler is calling the web service using the proxy built by ASP.NET AJAX. Note that because this is an asynchronous call, you have to pass in event handlers for both success and failure - that is where my GetDataSuccess() and GetDataFailed() functions come from. On success, I store the data, set the initial index to 0, and call the function to set the text in the TextBlock. Note I'm using document.getElementById() to find the Silverlight viewer. I'm using some inline server-side script to get the Id of the Silverlight viewer from my control (covered in a previous post) to pass to getElementById(). The viewer object has a content property upon which I can call findName() (also covered in a previous blog post) to get a reference to the TextBlock.

The last thing to do is handle the MouseLeftButtonDown event on the TextBlock so that the text changes when the user clicks on it. Here's that Javascript function:

function MyTextBlockClick( sender, args )
{
    if ( index >= data.length-1 )
    {
        index = 0;
    }
    else
    {
        index = index + 1;
    }
 
    UpdateTextBlock();
}

Here, I increment the index and when the index reaches the end of the list, I reset it to 0 to go back to the beginning. Then I call UpdateTextBlock() to display the new text.

You can see this example in action at http://www.killeverything.com/zak/Silverlight1/WebService1.aspx.

At the beginning of this post, I promised to show a more useful example. How about a Silverlight app that displays headlines from an RSS feed and lets you click through to the articles? If you've been reading my Silverlight posts, there shouldn't be anything too new going on here. I have just combined several of the concepts I've been learning and blogging about into a single Silverlight app. You can see it running here: http://www.killeverything.com/zak/Silverlight1/WebService2.aspx and the code for both the simple example and the RSS headline viewer are attached to this post. If you're a .NET head, you might want to look at the source for the web service where I used LINQ to XML to make parsing the RSS feed easy as cake. Oh, and I want to point out the clipping I had to add to the TextBlock. Support for MaxHeight and MaxWidth may be coming in Silverlight 2.0, but clipping is how it's done for now...

My Silverlight Control

Kevin — Sun, 23 Mar 2008 17:00:00 GMT

Putting a Silverlight viewer on a web page is a lot of work. You have to import the Silverlight.js file (and make sure it's deployed to the web server), create a div to contain the viewer, and write some Javascript code to call Silverlight.createObject(). To me, this is just begging for an ASP.NET control - so I whipped up one of my own.

So what do I want my control to do for me? Let's start at the top with the Silverlight.js file. I want this to be an embedded resource so that I don't always have to remember to copy it in to a new project. If you're not familiar with this technique, it's been around since .NET 2.0 - keep up! :) You just throw the Silverlight.js file into your project and set it's build action to "Embedded Resource". Here's a screenshot:

Add it to your project's AssemblyInfo.cs like this:

// Embeded Resources
[assembly: System.Web.UI.WebResource("knw.Silverlight.Silverlight.js", "application/x-javascript")]

Then my control's code tells the page where to find it like this:

Page.ClientScript.RegisterClientScriptInclude("Silverlight.js", Page.ClientScript.GetWebResourceUrl(this.GetType(), "knw.Silverlight.Silverlight.js"));

Here is a link to an article on Code Project that explains the technique in a bit more detail.

Next, I want my control to render the container div for the Silverlight viewer. This is pretty straightforward - I just override Render() and use the HtmlTextWriter that's passed in. Here's what it looks like:

protected override void Render(HtmlTextWriter writer)
{
    base.Render(writer);
 
    writer.AddAttribute("id", ID + "Div");
    writer.RenderBeginTag(HtmlTextWriterTag.Div);
    writer.RenderEndTag();
}

Note I'm just concatenating "Div" onto the existing ID of my control when building the div's id, but that should make it unique.

The only thing that's left is the call to Silverlight.createObject(). There are a few variables in this call that I thought could be exposed as properties of my control. Specifically, the path to the Xaml document, the height and width of the viewer, and the background color. I'm using C# 3.0, so I took advantage of another language feature - automatic properties. Here's what that code looks like:

public string Xaml { get; set; }
public int Height { get; set; }
public int Width { get; set; }
public Color BackgroundColor { get; set; }

Lastly, I need to build the actual javascript to create the Silverlight viewer and register it with the page to run as a startup script. Like this:

string createObjectScript = string.Format("<script>Silverlight.createObject( \"{0}\", document.getElementById( \"{1}Div\" ), \"{2}Ctrl\", {{ width:'{3}', height:'{4}', inplaceInstallPrompt:false,background:'{5}', isWindowless:'false', framerate:'24', version:'1.0' }},{{ onError:null,onLoad:null }},null );</script>", Xaml, ID, ID, Width, Height, ColorTranslator.ToHtml(BackgroundColor) );
 
Page.ClientScript.RegisterStartupScript( this.GetType(), ID + "Create", createObjectScript );

At first glance, that code looks pretty confusing. All it's actually doing is using string.Format() to build the call to Silverlight.createObject(). {0} is the path to the Xaml, {1} is the ID of the control + "Div" (the id of container div), {2} is the ID of the control + "Ctrl" (a unique id for the viewer itself), {3} is the width, {4} is the height, and {5} is the background color (converted from a System.Drawing.Color using the System.Drawing.ColorTranslator class). Oh yeah, and you have to escape curly braces when using string.Format() by doubling them.

Ok, that was a lot of work - what has it bought me? Well, now when I want to use Silverlight on an .aspx page, all I have to do is add a reference to my DLL, register it at the top of the .aspx page, and put the control on the .aspx page somewhere. Which looks like this:

<knw:Silverlight id="Silverlight1" runat="server" Xaml="MySilverlight.xaml" BackgroundColor="Gray" Height="200" Width="200" />

I will attach the code for both the control and an example of using it to this post. I'll be using this control in future Silverlight posts here - plus, I do intend to extend it to do more in the future (as I learn more about Silverlight). So, I'll try to post updates here from time to time. I hope it's useful to someone! :)

Silverlight - Simple Animation

Kevin — Sun, 23 Mar 2008 07:12:00 GMT

Seems I've fallen way behind on my Silverlight blogging as of late. A few weeks ago, I managed to get some simple animation working. So, I guess I should blog about it.

Animation is done by transforming your object. Each graphic element has a RenderTransform property to which you can assign a Transform object to modify your element in some way. The different types of Transform objects include RotateTransform, SkewTransform, ScaleTransform, and TranslateTransform. Let's look at an example.

<Ellipse MouseLeftButtonDown="EllipseClick" Height="50" Width="100" Canvas.Top="50" Canvas.Left="50" Fill="Black">
    <Ellipse.RenderTransform>
        <RotateTransform x:Name="EllipseXForm" Angle="90" />
    </Ellipse.RenderTransform>
</Ellipse>

This example is pretty boring - it just renders a 50 pixel high and 100 pixel wide ellipse, rotated 90 degrees (so that it instead appears 100 pixels high and 50 pixels wide). However, it illustrates the effect that a RotateTransform will have on an object. Also note that I have named the transform (the x:Name attribute). The purpose of that will soon become apparent.

Animations are defined within objects called Storyboards. Basically, a Storyboard defines a timeline of changes that should occur to properties of objects. For my example, I want to change the Angle property of the RotateTransform object over time (so that the Ellipse rotates slowly as we watch). Here is the Storyboard I have defined:

<Canvas.Resources>
    <Storyboard x:Name="EllipseStoryboard">
        <DoubleAnimation Storyboard.TargetName="EllipseXForm" Storyboard.TargetProperty="Angle" To="0" Duration="00:00:05" />
    </Storyboard>
</Canvas.Resources>

For this example, I have used a DoubleAnimation. This is because the property I want to change ("Angle") is of type double. There are many other animation objects available such as DecimalAnimation, Int32Animation, and ColorAnimation. The Storyboard.Targetname attribute tells the animation which object it is changing (here's where I use the name I gave my transform earlier) and Storyboard.TargetProperty indicates what property will be changed. The To attribute is the value the animation should end with and the Duration should be self-explanatory. Note again, I have named my Storyboard so that I can reference it later. Oh yeah, and the Storyboard is a resource, so it's defined inside the <Canvas.Resources /> element.

I'm going to need something to trigger the animation to begin. I've chosen to do it using a mouse click on the ellipse. So, I will need to add a MouseLeftButtonDown handler to the Ellipse. Now it looks like this:

<Ellipse MouseLeftButtonDown="EllipseClick" Height="50" Width="100" Canvas.Top="50" Canvas.Left="50" Fill="Black">...

And I need an EllipseClick() function defined in Javascript, so here's what I came up with:

<script type="text/javascript">
    function EllipseClick( sender, args )
    {
        sender.findName("EllipseStoryboard").Begin();
    }
</script>

I placed this directly in my .aspx file for this example. I don't think I've blogged about findName() before, but Silverlight elements define this method and it allows you to get a reference to any other Silverlight element by name. Here, I am using it to get the "EllipseStoryboard" Storyboard and executing it's Begin() method.

You can see this example in action at http://www.killeverything.com/zak/Silverlight1/EllipseRotate1.aspx

It's not quite what I wanted, though. The rotation is happening around the top left corner of the ellipse instead of the center. Luckily, this was easy to fix - the RotateTransform has CenterX and CenterY properties that allow you to define the point around which the object rotates. Knowing that the ellipse is 100 wide and 50 tall, this is what I changed the transform to look like:

<RotateTransform x:Name="EllipseXForm" Angle="90" CenterX="50" CenterY="25" />

You can see the finished example at http://www.killeverything.com/zak/Silverlight1/EllipseRotate2.aspx

I've also attached a ZIP with the files needed for these examples in case you want to play with them yourself.

Silverlight Day 2

Kevin — Sat, 23 Feb 2008 02:53:00 GMT

Today's goal is to display an image and react to a mouse click in some way. I actually started by reading the QuickStart that gets installed along with the Silverlight SDK. You can also find it at http://silverlight.net/quickstarts/silverlight10/default.aspx if you still don't have the SDK installed (and why don't you? Huh?)

It looks like all I need to display an image is an object set to fill with an ImageBrush. Something like this should work:

<Ellipse Height="100" Width="200" Canvas.Top="10" Canvas.Left="10">
    <Ellipse.Fill>
        <ImageBrush ImageSource="lolcat_quadcore.jpg" />
    </Ellipse.Fill>
</Ellipse>

Bingo, that did the trick. It looks like this:

Oh wait, I just found the Image object - no brush needed if you do it like this:

<Image Source="lolcat_quadcore.jpg" Canvas.Top="120" Canvas.Left="10" Height="100" />

Which looks like this:

Note that in the first case, the image was automatically stretched to fit the dimensions of the ellipse and in the second, I only specified a height - so the image was automatically scaled proportionally. Cool!

Now, processing mouse clicks. This appears to be amazingly easy as well. First, you need to declare the event handler in the XAML mark-up like this:

<Image Source="lolcat_quadcore.jpg" Canvas.Top="120" Canvas.Left="10" Height="100" MouseLeftButtonDown="ChangeLolcat" />

Then you just need a javascript function to handle the event - mine looks like this:

function ChangeLolcat( sender, args )
{
    if ( sender.Source == "lolcat_quadcore.jpg" )
        sender.Source = "lolcat_schroedinger.jpg";
    else
        sender.Source = "lolcat_quadcore.jpg";
}

In this case, because the MouseLeftButtonDown event is on the Image object, that's the object that gets passed in to the javascript function as "sender". I am simply changing the Source property from how it was defined in the XAML in response to the mouse click. And it works! (sorry I can't show you - I don't have a good place to host .NET code at the moment) I think I'm going to like working with Silverlight.

In case you want to download the code for this project and try it out yourself, I will ZIP it up and attach it to this blog post.

Silverlight Day 1

Kevin — Thu, 21 Feb 2008 01:16:00 GMT

So I finally set out to do something with Silverlight... I set a simple goal for myself tonight - I just wanted to see "Hello World". That should be easy, right?

First, I downloaded the Silverlight 1.0 SDK from http://www.microsoft.com/silverlight and installed it.

Second, I created a new web site in Visual Studio.

Third, I grabbed a copy of Silverlight.js and added it to the web site. For me, it was in C:\Program Files\Microsoft Silverlight 1.0 SDK\Tools\Silverlight.js.

I added a link to Silverlight.js in the HTML head of default.aspx. Like this:

<script type="text/javascript" src="Silverlight.js">
</script>

Next, I added a div in the HTML body of default.aspx and gave it an id. It doesn't need the runat=server attribute, just an id (it will only be reference from Javascript). Like this:

<div id="MySilverlightDiv">

</div>

Next, I created a XAML file. I know next to nothing about XAML yet, so I just used Google to "borrow" someone else's example code for now. My XAML file is called MySilverlight.xaml and looks like this:

<Canvas xmlns="http://schemas.microsoft.com/client/2007" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <TextBlock FontSize="40" FontFamily="Arial" Canvas.Top="20" Canvas.Left="20">
        Hello World!
    </TextBlock>
</Canvas>

Last thing I did was add the javascript to my HTML file to actually create the Silverlight object in my div:

<script type="text/javascript">
    Silverlight.createObject(
        "MySilverlight.xaml", 
        document.getElementById( "MySilverlightDiv"),
        "MySilverlightControl",
        { width:'400',
          height:'200',
          inplaceInstallPrompt:false,
          background:'#DDDDDD',
          isWindowless:'false',
          framerate:'24',
          version:'1.0' },
        { onError:null,
          onLoad:null },
        null );
</script>

That's the filename of my XAML file, the Id of my div, a unique Id for the Silverlight control itself, and some various parameters for Silverlight that I do not yet fully understand.

That's it. I hit my web site with a browser and there was my awesome Hello World!

Hopefully tomorrow I will have time to research XAML some more and do something a bit more interesting with Silverlight. I hope to extend this simple starter project and continue writing about it here, so if you're interested - copy/paste the code above and come back tomorrow! :)