Microphone Access in Silverlight App: LIVE

Just a heads up that the technique described earlier (using Flash and Javascript for microphone support in a Silverlight app) is live now in the Tutor.com Classroom!

You'll need to create an account and connect to a tutor to see it in action (click the 'Connect to a Tutor' button in the classroom to get started)--

don't save foreign key relationships for "the end"

consider adding foreign keys part of creating a table; if you haven't set up foreign key relationships, you haven't finished creating your table.

indexes, on the other hand, can be saved for "the end", once you get a better sense of how you're querying the tables and what's most optimal. but even with indexes, if you have a good sense when you're creating the table of how you're most likely to access the data, you're better off taking an educated guess early than never doing it late--

using SQL Profiler to monitor database calls

just in case anyone’s not familiar with SQL Profiler: this is the app that gives you low-level database monitoring so you can trace all database calls. you can customize what you monitor to get a variety of information.

so for example, if you want to set up a trace to see all database calls from your web server, launch Profiler, click the New Trace… button, connect locally, and go to the second tab:

• check checkboxes in the DatabaseName column
• click the Column Filters… button and add filters for:
  o DatabaseName Like => your database
  o NTUserName Like => nt identity you run your webserver as
  o TextData Like => exec

use format codes in report files

the best way to format datetime/number values in an RDL file is with the textbox’s Format property. you use the same format codes that you use in .NET and elsewhere, and you don’t have to worry about null values (null’s appear as empty strings). for example, common date format codes are:


d – 2/26/2009
D – Thursday, February 26, 2009
g – 2/26/2009 11:52am

some number/currency codes:

g – 1234
N – 1,234.00
C – $1234.12

if you forget the codes, you can get the VS2005 to show you them by right-clicking on the textbox and choosing ‘Properties’, going to the ‘Format’ tab, and clicking the ‘…’ button next to ‘Format code’.

report server rdl files in visual studio 2008

hacked my way through this mostly by accident; if you rename a .rdl file to .rdlc, then you can open the file in visual studio 2008 and use the same GUI for report file edits that you have in 2005. you don’t get the data and preview tabs, so you need to make data source edits manually in notepad, but if you find yourself with only vs 2008 and need to make .rdl edits, this is a good way to get some GUI help--

Microphone access in Silverlight via Flash and JavaScript

Silverlight is unquestionably a powerful tool for .NET application developers; using almost of all the same WPF skills,.NET developers can create rich internet applications (RIA) right out of the gate. However, Silverlight has no microphone/webcam support, and if you need this functionality in a cross-browser RIA, the common thinking is cross out Silverlight and pencil in Flash or Java.

While it's true that you'll need to dip into Flash or Java for microphone/webcam support (at least until Silverlight 3, and possibly not even then), there's no reason you can't take advantage of Silverlight as your base application host and selectively use Flash as necessary for Silverlight's missing features. Then, using a JavaScript bridge, you can get these browser technologies communicating with each other fairly painlessly. This integrated solution is what we're considering at Tutor.com when we add voice communication support to the Tutor.com Classroom, and this post will detail how to use Flash for microphone support inside a Silverlight application, where the button controlling the microphone on/off switch is in the Silverlight application.

Flash: Microphone management
First, we'll create a simple Flash movie (I'm using ActionScript 2) that manages and outputs microphone input. Thankfully, there's really very little code you need to write to do this; just note that your Flash movie must be at least 250x150 to allow room for the microphone Allow/Decline dialog, and if you don't want the movie to be visible, you need to set its background color to transparent.

As an aside, note that there's similarly very little code you need to write to connect to a Flash Media Server (FMS) for real-time communication, although the example here omits the FMS part. As another aside, note that the code for Flash webcam support is almost identical, except instead of a Microphone object you're working with a Camera object.

OK, so in the first frame of your Flash movie, write a function to access the microphone and monitor microphone activity:

var mic:Microphone = null;

function toggleVoice(isOn:Boolean)
{
  //setup the mic
  if (mic == null)
  {  
    //call Microphone.get() to access the microphone and prompt user with Allow/Decline dialog
    mic = Microphone.get();

    //Microphone.get() will return null if user declined access
    if (mic == null)
      return;

    //setup onActivity handler to get notification of mic activity
    mic.onActivity = function(active:Boolean)
    {   
      //call out to JavaScript bridge via ExternalInterface
      flash.external.ExternalInterface.call("IsTalking", active);
    };

    //create movie clip and attach mic to clip so we can hear output
    this.createEmptyMovieClip("sound_mc", this.getNextHighestDepth());
    sound_mc.attachAudio(active_mic);
  }

  //set the microphone gain as per the isOn input variable
  mic.setGain(isOn ? 50 : 0);
}

Below the function, add a callback handler that makes the function callable via JavaScript:

  flash.external.ExternalInterface.addCallback("ToggleVoice", this, toggleVoice);

Html: Application host page
When you add a Silverlight application to your solution in Visual Studio, the boilerplate html makes your application full-screen in the browser window (as in the Tutor.com Classroom); this is exactly what we ant. Next, we need to add our Flash html object tag. Silverlight is a bit picky about where you add this html tag since you need to preserve this 100% height style, so slot the Flash object tag immediately before the div tag, and style it with "position:absolute" so that it doesn't interfere in the html layout:

  <form id="form1" runat="server" style="height:100%;">
    <asp:ScriptManager ID="ScriptManager1" runat="server" />
            
    <object 
      id="voice" 
      style="position:absolute;"
      classid="clsid:d27cdb6e-ae6d-11cf-96b8-444553540000"
      codebase="http://fpdownload.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=8,0,0,0" 
      width="250" 
      height="150" 
      align="middle"
      ...
    />

    <div style="height:100%;">
      <asp:Silverlight     
        ID="Xaml1" 
        runat="server"                 
        ...
      />                                
    </div>
  </form>

Javascript: Flash/Silverlight bridge
Next, we'll create the JavaScript function that our Silverlight app will call, which will in turn call into our Flash movie to set the Microphone input status. Since our Flash movie registered the ToggleVoice() callback function using ExternalInterface, Flash added a JavaScript entry point to function when the Flash movie loaded:

<script language="javascript" type="text/javascript">
function toggleVoice(on) 
{
    var flashVoiceObject = thisMovie("voice");
    if (!flashVoiceObject)
        return;

    flashVoiceObject.ToggleVoice(on);
}

function thisMovie(movieName) {
    if (navigator.appName.indexOf("Microsoft") != -1) {
        return document.getElementById(movieName);
    }
    else {
        return document[movieName];
    }
}
</script>

We can also very simply call from JavaScript into Silverlight, and we'll do this to alert our Silverlight application when Flash notifies us of microphone activity:

function IsTalking(active) 
{
    //access the Silverlight application
    var control = document.getElementById("Xaml1");

    control.Content.Page.ToggleIsTalking(active);
}

Silverlight – Microphone toggle button
Finally, in Page.xaml, add a toggle button with Checked and Unchecked handlers, and an indicator that we'll show when the microphone is active:

<ToggleButton Content="Toggle Microphone Input" Checked="ToggleVoice_CheckedToggled" Unchecked="ToggleVoice_CheckedToggled" />

<TextBlock Text="You are talking..." Visibility="Collapsed" x:Name="IsTalkingIndicator" />

Then in Page.xaml.cs, implement the handler and call into the JavaScript function:

private void ToggleVoice_CheckedToggle(object sender, RoutedEventArgs e)
{
    //call js layer to set microphone state
    ScriptObject voiceToggleScriptObject = (ScriptObject)HtmlPage.Window.GetProperty("toggleVoice");

    ToggleButton tb = sender as ToggleButton;
    voiceToggleScriptObject.InvokeSelf(tb.IsChecked.Value);
}

Lastly, implement the ToggleIsTalking() function that we'll call from JavaScript when the Flash movie responds to the microphone's onActivity() event. You just need to decorate this function with the [ScriptableMember] attribute so that Silverlight registers the function with the JavaScript runtime:

[ScriptableMember]
public void ToggleVoiceOn(bool On)
{
    IsTalkingIndicator.Visibility = (On) ? Visibility.Visible : Visibility.Collapsed;
}

And that's it! You now have a relatively straightforward Flash <=>JavaScript <=> Silverlight solution that affords you the best of all worlds.

Tutor.com Classroom How-To #11: Build a Silverlight ToolbarButton user control

These How-To tips are taken from The Tutor.com Classroom: Architecture and techniques using Silverlight, WPF, and the Microsoft .NET Framework.

You can check out the Silverlight Tutor.com Classroom in "practice" mode, although the real experience is with a live tutor on the other side!

One of the controls missing out-of-the gate from Silverlight is the Toolbar. There is no magic to the WPF Toolbar (it’s just a control container that auto-docks itself and auto-styles its children), but for free you get the flat button look-and-feel that users expect at the top of an application.

In Silverlight, we have to manually create this look-and-feel. Since our application’s toolbar consists solely of buttons (both normal and toggle buttons), and since the buttons in our toolbar have the “icon followed by a text description” format, we can abstract this to build the ToolbarButton user control.

Begin by creating a new user control. Define the styles for the Hover and Pressed states in your user control’s Xaml resources:

<UserControl.Resources>
  <LinearGradientBrush x:Key="HoverBrush" StartPoint="0,0" EndPoint="0,1">
    <LinearGradientBrush.GradientStops>
      <GradientStop Color="White" />
      <GradientStop Color="#F8D28F" Offset=".3" />
    </LinearGradientBrush.GradientStops>
  </LinearGradientBrush>

  <LinearGradientBrush x:Key="PressedBrush" StartPoint="0,0" EndPoint="0,1">
    <LinearGradientBrush.GradientStops>
      <GradientStop Color="#F8D28F"/>
      <GradientStop Color="White" Offset=".3" />
    </LinearGradientBrush.GradientStops>
  </LinearGradientBrush>
</UserControl.Resources>

Then, use a Grid to hold two Border objects; one contains the image and the text label, and the other is a half-opaque, white filled Border that we use when the button is disabled.

<Grid>
  <Border x:Name="MainBorder" BorderThickness="1" CornerRadius="1" MouseEnter="Border_MouseEnter" MouseLeave="Border_MouseLeave" MouseLeftButtonUp="Border_MouseLeftButtonUp" Cursor="Hand" Margin="1">
    <StackPanel Orientation="Horizontal" Margin="5,1,5,1">
      <Image x:Name="BorderImage" Width="16" />
      <TextBlock x:Name="BorderTextBlock" Style="{StaticResource blackText}" Margin="5" />
    </StackPanel>
  </Border>
  <Border Background="#B2FFFFFF" x:Name="DisabledBackground" BorderThickness="1" CornerRadius="2" BorderBrush="#B2FFFFFF" Visibility="Collapsed" />
</Grid>

Next, wire up the IsEnabled, ToolTip, ImageSource, and Caption properties, and implement the hover and click functionality. Note that these properties are backed by dependency properties on the objects we defined in our Xaml.

public partial class ToolbarButton : UserControl
{
  bool m_IsEnabled = true;

  public new bool IsEnabled
  {
     set
     {
       MainBorder.Background = null;
       MainBorder.BorderBrush = null;
       DisabledBackground.Visibility = (value) ? Visibility.Collapsed : Visibility.Visible;
     }
  }  

  public string ToolTip
  {
    get { return ToolTipService.GetToolTip(MainBorder).ToString();}
    set { ToolTipService.SetToolTip(MainBorder, value);}
  }

  public ImageSource ImageSource
  {
    get { return BorderImage.Source;}
    set { BorderImage.Source = value;}
  }

  public string Caption
  {
    get { return BorderTextBlock.Text;}
    set { BorderTextBlock.Text = value;}
  }

  public bool IsToggleButton { get; set; }
  public bool IsToggled { get; set; }

  public event MouseButtonEventHandler Clicked;

  public ToolbarButton()
  {
    InitializeComponent();
  }

  private void Border_MouseEnter(object sender, MouseEventArgs e)
  {
    //if we're a toggle button and we're on...
    if (this.IsToggleButton && this.IsToggled)
      return;

    Border b = sender as Border;

    b.Background = Resources["HoverBrush"] as Brush;
    b.BorderBrush = new SolidColorBrush(ColorHelper.FromHexString("FFCA8103"));
  }

  private void Border_MouseLeave(object sender, MouseEventArgs e)
  {
    //if we're a toggle button and we're on...
    if (this.IsToggleButton && this.IsToggled)
      return;

    Border b = sender as Border;

    b.Background = null;
    b.BorderBrush = null;
  }

  private void Border_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
  {
    if (!m_IsEnabled)
      return;

    if (this.IsToggleButton)
    {
      this.IsToggled = !this.IsToggled;

      //set state
      Border b = sender as Border;
      b.Background = (this.IsToggled) ? Resources["PressedBrush"] as Brush : Resources["HoverBrush"] as Brush;
    }

    if (this.Clicked != null)
      this.Clicked(sender, e);
  }
}

Finally, in your container Xaml, use the ToolbarButton class inside a StackPanel with Orientation set to Horizontal:

<StackPanel Orientation="Horizontal">
  <local:ToolbarButton ImageSource="/Resources/board.png" Caption="Add Whiteboard" Clicked="AddWhiteboard_Click" Margin="1" />
  ...
</StackPanel>