A Style contains a collection of one or more Setter objects. Each Setter has a Property and a Value. The Property is the name of the property of the element the style is applied to. The Value is the value that is applied to the property.

Note:
If there is more than one setter in the setter collection with the same Property property value, the setter that is declared last is used. Similarly, if you set a value for the same property in a style and on an element directly, the value set on the element directly takes precedence.

You can set a Style on any element that derives from FrameworkElement. A style is most commonly declared with the x:Key attribute as a resource inside the Resources section and then referenced as a StaticResource. Because styles are resources, they obey the same scoping rules that apply to all resources, so where you declare a style affects where it can be applied. If, for instance, you declare the style in the root element of your application definition XAML file, the style can be used anywhere in your application.

You must set the TargetType property when you create a Style. If you do not, an exception is thrown.

You can change the values of individual properties that have been set within a style. For example, you can set the Template property at run time even if this property has been set by a style. Or you can add setters to the collection in Setters. However, as soon as that style is placed in use by a loaded object, the Style should be considered sealed. You can detect this state by checking the value of IsSealed for the Style. A style is considered to be in use as soon as it is referenced by a loaded object that is connected to the object tree and the Silverlight root visual. This point in time can be detected when the object where the Style property is set raises its Loaded event.

Styles in Silverlight differ from styles in Windows Presentation Foundation (WPF) in the following way:

• In Silverlight, you must add x:Key attributes to your custom styles and reference them as static resources. Silverlight does not support implicit styles applied using the TargetType attribute value.

In Silverlight 3, the write-once limitation on the Style property is removed. You can set the Style property to override a built-in default style. Setting the same style multiple times will not result in an exception.

The following example creates two styles: one for a TextBlock and one for a TextBox. Each style is applied to two instances of a control to create a uniform appearance for each TextBlock and TextBox. The example sets the Style property of each control by referencing the Style as a StaticResource.

Notice that in the style for the TextBox, the Margin property is set to 4, which means that the TextBox has a margin of 4 on all sides. To compensate for the length of the second TextBlock, which is shorter than the first TextBlock because "Last Name" takes less room than "First Name," a value of "6,4,4,4" is assigned to the Margin property on the second TextBox. This causes the second TextBox to have a different margin than what the style specifies, so that it aligns horizontally with the first TextBox.

<StackPanel>
  <StackPanel.Resources>
    <!--Create a Style for a TextBlock to specify that the
              Foreground equals Navy, FontSize equals 14, and
              VerticalAlignment equals Botton.-->
    <Style TargetType="TextBlock" x:Key="TextBlockStyle">
      <Setter Property="Foreground" Value="Navy"/>
      <Setter Property="FontSize" Value="14"/>
      <Setter Property="VerticalAlignment" Value="Bottom"/>
    </Style>

    <!--Create a Style for a TextBlock that specifies that
              the Width is 200, Height is 20, Margin is 4,
              Background is LightBlue, and FontSize is 14.-->
    <Style TargetType="TextBox" x:Key="TextBoxStyle">
      <Setter Property="Width" Value="200"/>
      <Setter Property="Height" Value="30"/>
      <Setter Property="Margin" Value="4"/>
      <Setter Property="FontSize" Value="14"/>
      <Setter Property="Background">
        <Setter.Value>
          <LinearGradientBrush StartPoint="0,0.5" EndPoint="1,0.5">
            <GradientStop Color="White" Offset="0.0"/>
            <GradientStop Color="LightBlue" Offset="0.5"/>
            <GradientStop Color="Navy" Offset="1"/>
          </LinearGradientBrush>
        </Setter.Value>
      </Setter>
    </Style>
  </StackPanel.Resources>

  <!--Apply the TextBlockStyle and TextBoxStyle to each 
          TextBlock and TextBox, respectively.-->
  <StackPanel Orientation="Horizontal">
    <TextBlock Style="{StaticResource TextBlockStyle}">
              First Name:
          </TextBlock>
    <TextBox Style="{StaticResource TextBoxStyle}"/>
  </StackPanel>
  <StackPanel Orientation="Horizontal">
    <TextBlock Style="{StaticResource TextBlockStyle}">
              Last Name:
          </TextBlock>
    <TextBox Style="{StaticResource TextBoxStyle}"  
                   Margin="6,4,4,4"/>
  </StackPanel>
</StackPanel>

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

Reference