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C# Silverlight - Using Sliders [Beginner]


Being the month of Silverlight, I decided to get off my PHP and JS butt, and learn something new. I am incredibly new to the whole silvery-light thing, but luckily with Visual Studio on your side, it is pretty easy to get things going. I am also using VS2010, which makes the whole experience a grand opening of new stuff for me.

So to begin my foray into Silverlight, I did something easy, but slightly useful at the same time. What I have made is a set of three sliders that represent a RGB value, which in turn changes the color of some text. It is some pretty short code, but it does showcase how to change the color of TextBlock text, which took me a few minutes to find.

[silverlight width="400" height="300" src="SilverlightApplication.xap" border="true"]
To begin with, lets get the XAML out of the way:
<UserControl x:Class="SilverLightColorSliders.Page"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d"
    d:DesignHeight="300" 
    d:DesignWidth="400" 
    xmlns:basics="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls">

  <Grid x:Name="LayoutRoot" Background="White">
    <Slider Height="22" Name="redSlider" Width="100" Maximum="255" 
      ValueChanged="slider_ValueChanged" SmallChange="1" 
      Margin="145,118,0,0" HorizontalAlignment="Left" 
      VerticalAlignment="Top" />
    <Slider Height="22" HorizontalAlignment="Left" Margin="145,146,0,0" 
      Name="greenSlider" VerticalAlignment="Top" Width="100" Maximum="255" 
      ValueChanged="slider_ValueChanged" SmallChange="1" />
    <Slider Height="22" HorizontalAlignment="Left" Margin="145,174,0,0" 
      Name="blueSlider" VerticalAlignment="Top" Width="100" Maximum="255" 
      ValueChanged="slider_ValueChanged" SmallChange="1" />
    <TextBlock Height="30" Margin="96,79,96,191" Name="textBlock1" 
      Text="Switch on the Code" Width="207" FontSize="20" 
      HorizontalAlignment="Left" VerticalAlignment="Top" />
    <TextBlock Height="21" HorizontalAlignment="Left" Margin="266,118,0,0" 
      Name="redValue" Text="0" VerticalAlignment="Top" Width="44" />
    <TextBlock Height="21" HorizontalAlignment="Left" Margin="266,145,0,0" 
      Name="greenValue" Text="0" VerticalAlignment="Top" Width="44" />
    <TextBlock Height="21" HorizontalAlignment="Left" Margin="266,172,0,0" 
      Name="blueValue" Text="0" VerticalAlignment="Top" Width="44" />
    <TextBlock Height="21" HorizontalAlignment="Left" Margin="80,119,0,0" 
      Name="redLabel" Text="Red" VerticalAlignment="Top" Width="59" 
      TextAlignment="Right" />
    <TextBlock Height="21" HorizontalAlignment="Left" Margin="80,173,0,0" 
      Name="blueLabel" Text="Blue" VerticalAlignment="Top" Width="60" 
      TextAlignment="Right" />
    <TextBlock Height="21" HorizontalAlignment="Left" Margin="80,146,0,0" 
      Name="greenLabel" Text="Green" VerticalAlignment="Top" Width="59" 
      TextAlignment="Right" />
  </Grid>
</UserControl>
 
The important things we have here are the sliders and the main "SOTC" label. Of course we have other labels that help us know what we are changing, but essentially all we need are the sliders and the text to recolor. The sliders are set to a max of 255, which is the maximum value for any RGB value.

The key to changing the color of the text inside the TextBlock is an abstract object called a Brush. Since it is abstract, we can't just use it willy-nilly. Thankfully, C# has objects we can use for exactly what we need to do, in our case a SolidColorBrush object.

To use this brush, all we need to do is give it a color object with the RGB values we want. The C# Code will end up looking something like so:
    private void slider_ValueChanged(object sender, 
      RoutedPropertyChangedEventArgs<double> e)
    {
      Color textColor = new Color();
      textColor.A = 255;
      textColor.R = (byte)redSlider.Value;
      redValue.Text = Math.Round(redSlider.Value).ToString();
      textColor.G = (byte)greenSlider.Value;
      greenValue.Text = Math.Round(greenSlider.Value).ToString();
      textColor.B = (byte)blueSlider.Value;
      blueValue.Text = Math.Round(blueSlider.Value).ToString();

      SolidColorBrush textBrush = new SolidColorBrush(textColor);
      textBlock1.Foreground = textBrush;
    }
 
What we want to do is change the color when any of the sliders change their value. So this event is tied to all of the sliders, which makes for great code reuse. What the event is actually doing is quite simple. We create a new C# color object, giving it a full value for alpha. This way there will be no transparency. Next, for each of the three RGB values, we pass it to the color object then display the value in the corresponding TextBlock. Finally we create a SolidColorBrush with the Color object and set the Foreground property of the TextBlock object. The Foreground property is actually a Brush that controls the color of the text inside the TextBlock, so all we have to do is set that property to our Brush object. The end result is text that changes color when we change the color's value.

Well, that is pretty much all there is to this tutorial. I hope this was informative, and there are sure to be more Silverlight tutorials to come.
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