At my previous company, we created our RIAs using Flex with graphical assets created in Flash. In Flash, you could simply lay out your graphics for different states, i.e. rollover, disabled.

Now, I'm working on a Silverlight 3 project. I've been given a bunch of images that need to serve as the graphics for buttons that have a rollover, pressed, and normal state. I cannot figure out how to simply create buttons with different images for different visual states in Visual Studio 2008 or Expression Blend 3.

Here's where I am currently. My button is defined like this in the XAML:

<Button Style="{StaticResource MyButton}"/>

The MyButton style appears as follows:

<Style x:Key="MyButton" TargetType="Button">
  <Setter Property="Template">
    <Setter.Value>
      <ControlTemplate TargetType="Button">
        <Image Source="/Assets/Graphics/mybtn_up.png" Width="54" Height="24">
          <VisualStateManager.VisualStateGroups>
            <VisualStateGroup x:Name="FocusStates">
              <VisualState x:Name="Focused"/>
              <VisualState x:Name="Unfocused"/>
            </VisualStateGroup>
            <VisualStateGroup x:Name="CommonStates">
              <VisualState x:Name="Normal"/>
              <VisualState x:Name="MouseOver"/>
              <VisualState x:Name="Pressed"/>
              <VisualState x:Name="Disabled"/>
            </VisualStateGroup>
          </VisualStateManager.VisualStateGroups>
        </Image>
      </ControlTemplate>
    </Setter.Value>
  </Setter>
</Style>

I cannot figure out how to assign a different template to different states, nor how to change the image's source based on which state I'm in. How do I do this? Also, if you know of any good documentation that describes how styles work in Silverlight, that would be great. All of the search results I can come up with are frustratingly unhelpful.

Edit:

I found a way to change the image via storyboards like this:

<Style x:Key="MyButton" TargetType="Button">
  <Setter Property="Template">
    <Setter.Value>
      <ControlTemplate TargetType="Button">
        <Image Source="/Assets/Graphics/mybtn_up.png" 
               Width="54" Height="24" x:Name="Image">
          <VisualStateManager.VisualStateGroups>
            <VisualStateGroup x:Name="FocusStates">
              <VisualState x:Name="Focused"/>
              <VisualState x:Name="Unfocused"/>
            </VisualStateGroup>
            <VisualStateGroup x:Name="CommonStates">
              <VisualState x:Name="Normal"/>
              <VisualState x:Name="MouseOver">
                <Storyboard Storyboard.TargetName="Image" 
                            Storyboard.TargetProperty="Source">
                  <ObjectAnimationUsingKeyFrames>
                    <DiscreteObjectKeyFrame KeyTime="0" Value="/Assets/Graphics/mybtn_over.png"/>
                  </ObjectAnimationUsingKeyFrames>
                </Storyboard>
              </VisualState>
              <VisualState x:Name="Pressed">
                <Storyboard Storyboard.TargetName="Image" 
                            Storyboard.TargetProperty="Source">
                  <ObjectAnimationUsingKeyFrames>
                    <DiscreteObjectKeyFrame KeyTime="0" Value="/Assets/Graphics/mybtn_active.png"/>
                  </ObjectAnimationUsingKeyFrames>
                </Storyboard>
              </VisualState>
              <VisualState x:Name="Disabled"/>
            </VisualStateGroup>
          </VisualStateManager.VisualStateGroups>
        </Image>
      </ControlTemplate>
    </Setter.Value>
  </Setter>
</Style>

However, this seems like a strange way of doing things to me. Is there a more standard way of accomplishing this?