02May

The dream of "half-automatic" Automation Properties

Everyone who has worked with WPF knows the interface INotifyPropertyChanged. It only defines the PropertyChanged-event, that should be called when a property's value has been changed. The PropertyChanged-event is used by WPF's Data Binding. Normally a class fires the event in the set-Accessors of its properties. And that's the problem why you can't use Automation Properties for classes that implement INotifyPropertyChanged. (more…)
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06Apr

Take Snapshots of Videos with WPF

With WPF's Imaging-Classes you can take snapshots of any Visual. The snapshot can be saved in any common Image-Format, like e.g. JPG. Let's take a look at a pretty short example, that shows how easy this can be done. The example takes snapshots of a Video. The following Window contains a MediaElement and a Button. The MediaElement plays the Video thomasOnBoard.wmv. The Button defines an Eventhandler for the Click-Event. It takes a snapshot of the video, when you click it. 
<Window x:Class="SnapShots.Window1"
    xmlns=http://schemas.microsoft.com/winfx/2006/xaml/...
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Window1" Height="300" Width="300"

 ResizeMode="NoResize">
  <StackPanel>
   <MediaElement x:Name="media" Height="200" Stretch="Fill">
      <MediaElement.Triggers>
       <EventTrigger RoutedEvent="MediaElement.Loaded">
        <BeginStoryboard>
         <Storyboard>
          <MediaTimeline
Source="thomasOnBoard.wmv"
           RepeatBehavior="Forever"/>
         </Storyboard>
        </BeginStoryboard>
       </EventTrigger>
      </MediaElement.Triggers>
     </MediaElement>
     <Button Click="Button_Click" Content="Snapshot"/>
  </StackPanel>
</Window>
Let's look at the Eventhandler of the Button. An instance of the RenderTargetBitmap-class is created with some parameters about image-size, dots per inch (dpi) and Pixelformat. The Render-Method gets the MediaElement as a parameter, so MediaElements visual appearance is stored in the RenderTargetBitmap in memory. With a JpegBitmapEncoder and a FileStream the Image is written as a JPG to disk. That's it. 
void Button_Click(object sender, RoutedEventArgs e)
{
  Size dpi = new Size(96,96);
  RenderTargetBitmap bmp = 
    new RenderTargetBitmap(300, 200, 
      dpi.Width, dpi.Height, PixelFormats.Pbgra32);
  bmp.Render(media);

  JpegBitmapEncoder encoder = new JpegBitmapEncoder();
  encoder.Frames.Add(BitmapFrame.Create(bmp));

  string filename = Guid.NewGuid().ToString()+".jpg";
  FileStream fs = new FileStream(filename,FileMode.Create);
  encoder.Save(fs);
  fs.Close();

  Process.Start(filename);
}
Instead of taking the picture in the Button_Click eventhandler, you could create a Timer and take an Image every 0.1s. That allows you to extract an image-sequence of your videos. As it works for any Visual, and everything that's on the screen in a WPF-Application is a visual, there are many things you can do with it. You could create a snapshot of an Image drawn to an inkCanvas, upload it to a webserver to display it on a webpage etc.
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23Feb

Built-in DataGrid for WPF is planned

Yes, they are planning to release it. Really great news. Today there's no DataGrid for WPF-applications as part of .NET Framework 3.5. There are only third-party controls like the Grid from Xceed or Infragistics. Have you ever built a business application without a DataGrid? I haven't. I'm really happy to hear that microsoft will release a DataGrid for WPF as part of .NET. That wouldn't make thirdparty-components necessary (If you don't need all functionality e.g. Infragistics provides). I hope the DataGrid for WPF will be more like the DataGridView of WinForms in NET 2.0, and not like DataGrid in .NET < 2.0. :-) Take a look at the .NET 3.5 roadmap on Scott Guthries blogpost. There's a little line containing this information about a planned built-in DataGrid by end 2008. Also some other missing controls are planned, like Calendar/DatePicker.
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07Jan

Give your blog-code the "Visual Studio"-look

How do you write a blog-entry with code that has the same syntax-highlightning like Visual Studio has? I mean this look: <Code> <Code.Style> <Style TargetType="{x:Type Code}"> <Setter Property="IsReallyGoodReadable" Value="Yes"/> </Style> </Code.Style> </Code> There are many different blug-ins. But only a few get the code exactly look like in Visual Studio. To get your code looking like the code above, you have to do 2 steps (with a small 3rd css-step): 1. Install Live Writer: http://get.live.com/WL/config_all - LiveWriter is a tool for writing blog entries offline 2. Go to the Live Gallery and download the "Paste from Visual Studio add in": Link to the Paste-Plugin In LiveWriter you can paste the code direct from visual studio by clicking on the link of the plugin. After you've written your entry, you upload it, edit it online and finally publish it. Special things for Firefox: In Firefox the fontsize of the code is much smaller than in Internet Explorer 7. Fortunately the pasted code is inside a pre-Tag. The pre-Tags' class-Attribut is set to "code". So you can easily point to the "code" in your css and give the font a fixed size, and it'll look equal in Firefox and Internet Explorer. 3. The css-Step I've set the fontsize in the css-File of my Wordpress theme to 10. The gray background of the code and the dotted border is also specified in my css. Just past the following in your css to make the code exactly looking like the snippet above and the css-snippet itself: .code { font-family: Courier New; font-size: 10pt; background-color: #EEEEEE; margin: 0px; padding: 5px; border: dotted 1px #CCCCCC; } Tips: It's a good practice to enter all linebreaks in Visual Studio before you paste the code into LiveWriter. I normally paste and delete and paste and delete and so on... until it fits. Find more tips on Karl Shifflets blog Thanks to: Luca Bolognese and Charlie Calvert from Microsoft. They linked me to the plugin. Thanks also to Karl Shifflet who initiated this entry. I hope this entry helps you to write your post with this format. How do you paste your code today? Do you know other plugins that give your blog-code the Visual Studio-look?
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