Problem with statemanager in SL4 - silverlight-4.0

Question

I have a togglebotton
<ToggleButton Padding="1">
<TextBlock>
<Underline>Week</Underline>
</TextBlock>
</ToggleButton>
and what I need to change is set underline to false, when togglebutton is unchecked, and set it to true, when control is ckecked.
and now I have only
<ToggleButton Padding="1">
<VisualStateManager.VisualStateGroups>
<VisualStateGroup x:Name="CommonStates">
<VisualState x:Name="IsChecked">
<Storyboard Duration="0:0:0">
and I can't figure out what next .
I'm not stick with conception with textblock. Text in the ToggleButton should be underline and that's all.

Answer 1

In order to use VisualStateManager you would have to redefine the template of the ToggleButton - take a look at the MSDN ToggleButton Syles. Instead of that you can use Blend's triggers. First add to your project System.Windows.Interactivity.dll and Microsoft.Expression.Interactions.dll provided by Expression Blend SDK and then use the following code:
<ToggleButton x:Name="toggleButton" Padding="1">
<TextBlock x:Name="textBlock">
<i:Interaction.Triggers>
<ei:DataTrigger Binding="{Binding IsChecked, ElementName=toggleButton}" Value="True">
<ei:ChangePropertyAction PropertyName="TextDecorations">
<ei:ChangePropertyAction.Value>
<TextDecorationCollection>Underline</TextDecorationCollection>
</ei:ChangePropertyAction.Value>
</ei:ChangePropertyAction>
</ei:DataTrigger>
<ei:DataTrigger Binding="{Binding IsChecked, ElementName=toggleButton}" Value="False">
<ei:ChangePropertyAction PropertyName="TextDecorations"/>
</ei:DataTrigger>
</i:Interaction.Triggers>
Week
</TextBlock>
</ToggleButton>
The ei: and i: are the following:
xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
xmlns:ei="http://schemas.microsoft.com/expression/2010/interactions"