Using Effects in Blend and C#
       by kirupa  |  19 August 2009

One of the new features introduced in Silverlight 3 is support for what are known as Effects (also known as pixel shaders or shader effects) that you have in WPF. In a nutshell, shader effects allow you to affect what you see on the screen in cool and interesting ways.

For example, play with the slider in my following example to adjust how blurry the image gets:

Get Microsoft Silverlight

[ the graphic is from Daniel Cook's amazing Small World graphic set ]

The blurriness is not a special image or any custom code that creates that illusion. It is a shader effect that comes with Silverlight, called Blur, that I simply applied to the image instead. In this short tutorial, let's look at how to use effects both from inside Blend as well as in C#.

Using Effects in Blend
To use Effects in Blend, you first need something visual to apply your effect to. It can be anything, but I will use a Button for my example. So, on my artboard, I have a button displayed:

[ drag and drop a button on the artboard ]

To apply an effect, go to the Assets panel, find the Effects category, and click on it:

[ the Effects category displays the effects you can use]

When you have the Effects category selected, today in both WPF and Silverlight, you should see just two effects - BlurEffect and DropShadowEffect. We are interested in the BlurEffect right now, so click on the BlurEffect and drag and drop it onto your button.

You can drag the effect directly onto your button on the artboard, or you can drop it onto your button in the object tree. The object tree approach displays a cool tooltip though:

[ drag and drop the Effect on your button ]

Once you have applied the effect to your button, your button will now look blurry:

[ your button is now blurry! ]

You can tell an effect is applied not only by just looking at the effects of the effect (ha!) on the element, but you can tell by looking at the object tree as well. The effect will always be located directly under the element it has been applied to:

[ the effect icon is visible directly below the element you applied the effect to ]

The blurriness of the button is fully customizable. By default, when you drop an effect onto an element, the effect automatically gets selected and the Properties Inspector displays any properties the effect exposes...such as Radius for the BlurEffect:

[ the properties inspector displays properties of your selected effect ]

If you don't see your effect's properties displayed, be sure to select the effect in the object tree.

Adding Effects in Code
There will be cases where you need to add effects using nothing but code. Doing that is, obviously, not as easy as using the Blend UI, but it isn't the most difficult thing either.

The code for adding a BlurEffect to an element called foo is as follows:

BlurEffect effect = new BlurEffect();
effect.Radius = 10;
foo.Effect = effect;

Just make sure to add System.Windows.Media.Effects using statement to your project:

using System.Windows.Media.Effects;

That is all there is to the code, and it should be pretty self explanatory on what actually happens. The general template for adding an effect is always:

  1. Declare and initialize the effect object you are planning on using. That is what we are doing in the first line.

  2. Set any properties on the effect that are not going to be default. In our example, I set the Radius property to 10.

  3. Assign the effect object to the Effect property of the element you wish to apply the effect to. This is the equivalent of dragging the effect onto an element using Blend's UI. Most (if not all) visual elements in Silverlight and WPF have the Effect property that you can set an effect you declared to.

That is all there is to effects. Because Silverlight and WPF only ship with two effects, your choices out of the box are limited only to Drop Shadow and Blur. Currently, adding your own custom effects is not trivial, and I may cover in a future tutorial how to do just that.

Getting back to the tutorial at hand, if you are interested in looking at my final version of the project, feel free to download the source files by clicking the link below:

Download Final Source Files


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