Silverlight

Silverlight 2: How to get a Color or a SolidColorBrush from a String (by ColorName) for Binding

ftom — Thu, 21 Aug 2008 18:44:33 GMT

I ran into this problem last night when I was preparing a bigger demo for my blog. It took me some time to find a solution for a simple but important piece. I decided to go ahead an break the demo down into smaller pieces.

The problem is simple: How to get a Color Object from a String of Text (e.g. AliceBlue, Blanched Almond, or just Blue)

At the Silverlight Forum I found a good link which I used as a base:
http://silverlight.net/forums/p/9134/28837.aspx

Here is my modified snippet:

private Color getColorFromString(string colorString)
{
Type colorType = (typeof(System.Windows.Media.Colors));
if (colorType.GetProperty(colorString) != null)
{
   object color = colorType.InvokeMember(colorString, BindingFlags.GetProperty, null, null, null);
   if (color != null)
   {
     return (Color)color;
   }
   throw new InvalidCastException("Color not defined");
}

I decided to throw an InvalidCastException so I can process the Exception later on. Of course this also could be the place to return a default Color right now. I just like to keep it more flexible.

To be able to use it as a Converter Parameter in UI Bindinding,  I wrapped it into a ColorConverter:
public class ColorConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
   if (value.GetType() == typeof(String))
   {
     try
     {
       Color c = getColorFromString(value as string);
       return new SolidColorBrush(c);
     }
    catch (InvalidCastException ex)
    {
      return null;
    }
}
return null;
}

public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
throw new NotImplementedException();
}
}

I decided here to return null in case something goes wrong. In this case the binding Framework Element has the chance to use an attached Property form its parent.

Let me know if you have an issus with it or if you have a suggestion to make the code better. Feedback is always highly welcome.

Next time I will present the rest of the demo with a full blown solution. So stay tuned in.

Tom

P.S.: Is there a tool to format the codesnippets automatically?

Silverlight (SL2B2) Bug in Blend (Preview 2.5)

ftom — Mon, 18 Aug 2008 13:37:09 GMT

To gain more experience with Blend I completed some tutorials on

http://www.nibblestutorials.net/

Inspite of learning more about Blend it was interesting to see a full blown Silverlight app. It is very good looking but not being able to use the back button is kind of weird. My take on that is: For Webuser always provide a way to navigate back (I know windows user do not need it because they just use their undo button…)

But I really like how they guide you through the basics.

Also I was pleasantly surprised that the actual Xaml was not to much screwed up by Blend.

Of course there is always a but:

"But" I found on Bug with Blend in the 2.5 Preview version.

Coming from WPF and using Dynamic Resources you don’t spend too much attention of the sequence of elements in the Resource Dictionary.

But as you all know (I hate this expression – but I guess I have to use it at least once in my blog) Silverlight does only support StaticResources. Bummer.

This means when you add items to the ResourceDictonary - which itself use StaticResources - Blend gets confused. It compiles fine but you get a runtime error.

It is easy to fix – you just switch into Xaml mode and move the items to the correct position.

Note the CRL instantiated the items by sequence and if it does not find a StaticResource it throws an exception.

I have to admit somehow it was satisfying to see, that you still need Xaml knowledge and that all the effort to learn it was not a waste of time (or maybe it was just good for my ego to realize I am soooo smart that I can actually find a bug)

I wish all you Xaml people a good start into your Xaml week

Tom

Silverlight here I come - Fun and Pain in the whatever (PitW)

ftom — Tue, 12 Aug 2008 14:56:40 GMT

The last 3 months I was writing a couple of smaller Silverlight apps. Coming coming from WPF I have to admit is is similar but still so different.

They really stripped it down. So what do I really miss:

No Binding to UI Elements in XAML (this really sucks...). I found a work around to bind to a State class, but it is not as elegant
No {DynamicResource}. Only Static. This also really sucks. No skin change on the fly possible.
No Event Triggers (e.g. onMouse over,...) but in SL2B2 they at least have the Visual State Manager
Debugging is a pain in the whatever....

But I have to admit besides all these missing parts I think it is the right way to go. It is just lighter than WPF and the IDE is faster (at least on my machine)... It just is a stronger focus on the UI.

But enough of whining... let's look at the cool new features: Visual State Manager (VSM)

This is what will also replace all the UI-Triggers in WPF in the next version. And it integrates "smoothly" into Blend. I am not a big fan of Blend (I just love coding in XAML - like good old html days) but even I have to admit for a first beta version it is really really impressive!

I think the best article which is a must about the VSM is from one of the Developer of Silverlight:

http://scorbs.com/work

She has a 4 part series about VSM. If you plan to use WPF or Silverlight in the future => READ IT !!!!!!!!
This will save you lots of pain when you look at Blend code.

So that's it for today. I guess in the next blogs I will focus more on snippets and pain in the whatever (pitw) of my daily life with Silverlight

All the best to all you geeks

Tom