Develop Reference

Swapping brushes in VisualStateManager

I'm trying to create a custom style for a brush with a glass-type look. I have it looking the way I want it, but I can't get the Pressed behavior to work.
The pressed look is simply the normal look with one of the brushes reversed. I have set both brushes as resources and tried ObjectAnimationUsingKeyFrames, but it doesn't seem to take. The idea is something along the lines of this:
<VisualState x:Name="Pressed">
<Storyboard>
<!-- swap the brush from {StaticResource ButtonGlassBrushNormal} to
{StaticResource ButtonGlassBrushPressed -->
</Storyboard>
</VisualState>
Here are my resources and style:
<LinearGradientBrush x:Key="ButtonGlassBrushNormal" EndPoint="0.5,1" StartPoint="0.5,0">
<GradientStop Color="#00000000" Offset="0.31"/>
<GradientStop Color="White"/>
</LinearGradientBrush>
<LinearGradientBrush x:Key="ButtonGlassBrushPressed" EndPoint="0.5,0" StartPoint="0.5,1">
<GradientStop Color="White"/>
<GradientStop Color="#00000000" Offset="0.31"/>
</LinearGradientBrush>
<ControlTemplate x:Key="ButtonControlTemplate1" TargetType="{x:Type Button}">
<Grid>
<VisualStateManager.VisualStateGroups>
<VisualStateGroup x:Name="CommonStates">
<VisualState x:Name="Normal" />
<VisualState x:Name="Pressed">
<Storyboard>
<ObjectAnimationUsingKeyFrames
Storyboard.TargetName="_glassBorder"
Storyboard.TargetProperty="Background"
Duration="0:0:1"
RepeatBehavior="Forever">
<ObjectAnimationUsingKeyFrames.KeyFrames>
<DiscreteObjectKeyFrame KeyTime="0:0:1" Value="{StaticResource ButtonGlassBrushPressed}" />
</ObjectAnimationUsingKeyFrames.KeyFrames>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
<Border BorderBrush="Black" BorderThickness="1" HorizontalAlignment="Left" Width="{TemplateBinding Width}" Height="{TemplateBinding Height}" VerticalAlignment="Top" Margin="0,0,0,-21.167" CornerRadius="5">
<Border.Background>
<LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
<GradientStop Color="Black" Offset="0"/>
<GradientStop Color="#FF803A3A" Offset="1"/>
</LinearGradientBrush>
</Border.Background>
<Border BorderThickness="1" CornerRadius="5" x:Name="_glassBorder" Background="{StaticResource ButtonGlassBrushNormal}">
<ContentPresenter HorizontalAlignment="Center" VerticalAlignment="Center"/>
</Border>
</Border>
</Grid>
</ControlTemplate>
I'm guessing this will be head-slappingly simple, but what am I doing wrong here?

Do not set a Duration on the Storyboard, and perhaps a zero KeyTime. Moreover, you'll also have to declare the MouseOver state, otherwise the Pressed state will persist until the mouse leaves the Button:
<VisualStateGroup x:Name="CommonStates">
<VisualState x:Name="Normal"/>
<VisualState x:Name="MouseOver"/>
<VisualState x:Name="Disabled"/>
<VisualState x:Name="Pressed">
<Storyboard>
<ObjectAnimationUsingKeyFrames
Storyboard.TargetName="_glassBorder"
Storyboard.TargetProperty="Background">
<ObjectAnimationUsingKeyFrames.KeyFrames>
<DiscreteObjectKeyFrame KeyTime="0:0:0"
Value="{StaticResource ButtonGlassBrushPressed}"/>
</ObjectAnimationUsingKeyFrames.KeyFrames>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
</VisualStateGroup>

That's the way you should do if you don't care about animations (like me):
<VisualState x:Name="Pressed">
<Storyboard>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Background" Storyboard.TargetName="_glassBorder">
<DiscreteObjectKeyFrame KeyTime="0" Value="{StaticResource ButtonGlassBrushPressed}"/>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>

Changing the BorderBrush of a button during MouseOver

To start, it's important to note that I'm doing this in Silverlight, so Style Triggers aren't available.
I'm trying to create a custom Button template. I've avoided doing this in the past, so this is my first attempt at something like this. I want a button that is essentially transparent. When I mouseover, the button border should appear. When I click, I want the background to darken a bit. The trouble I'm having right now is getting the BorderBrush to change on mouseover.
Note, in my test code here I'm starting with the borderbrush as visible and trying to make it invisible on the mouseover, which is the opposite of what I'm trying to accomplish in the end.
<DoubleAnimation Duration="0" To="0" Storyboard.TargetProperty="(UIElement.Opacity)" Storyboard.TargetName="BorderBrush" />
Was my best attempt, but I just get an error saying 'Cannot resolve TargetName BorderBrush.'
Also, how would I start with my LinearGradient for my borderbrush defined like it is, but just with the opacity set to 0 (so that I can set it to 1 when I want it to appear).
Below is my entire template:
<Style x:Key="ButtonStyle_menu" TargetType="Button">
<Setter Property="Foreground" Value="#000000"/>
<Setter Property="Padding" Value="3"/>
<Setter Property="BorderThickness" Value="1"/>
<Setter Property="BorderBrush" >
<Setter.Value>
<!--Value="#FF000000"-->
<LinearGradientBrush>
<GradientStop Color="#FFA3AEB9" Offset="0" />
<GradientStop Color="#FF8399A9" Offset="0.375" />
<GradientStop Color="#FF718597" Offset="0.375" />
<GradientStop Color="#FF3C4400" Offset="1" />
</LinearGradientBrush>
</Setter.Value>
</Setter>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="Button">
<Grid>
<VisualStateManager.VisualStateGroups>
<VisualStateGroup x:Name="CommonStates">
<VisualState x:Name="Normal"/>
<VisualState x:Name="MouseOver">
<Storyboard>
<!--<DoubleAnimation Duration="0" To="0" Storyboard.TargetProperty="(UIElement.Opacity)" Storyboard.TargetName="BorderBrush" />-->
<DoubleAnimation Duration="0" To="0" Storyboard.TargetProperty="(frameworkelement.Opacity)" Storyboard.TargetName="BorderBrush" />
</Storyboard>
</VisualState>
<VisualState x:Name="Pressed"/>
<VisualState x:Name="Disabled">
<Storyboard>
<DoubleAnimation Duration="0" To="0.4" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="DisabledVisualElement"/>
</Storyboard>
</VisualState>
</VisualStateGroup>
<VisualStateGroup x:Name="FocusStates">
<VisualState x:Name="Focused">
<Storyboard>
<DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="FocusVisualElement"/>
</Storyboard>
</VisualState>
<VisualState x:Name="Unfocused"/>
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
<Border x:Name="Background" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}">
<Border.Background>
<SolidColorBrush Opacity="0" />
<!--
<LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
<GradientStop Color="#FF707070" Offset="0"/>
<GradientStop Color="#FF666666" Offset="0.49"/>
<GradientStop Color="#FF5e5e5e" Offset="0.51"/>
<GradientStop Color="#FF535353" Offset="1"/>
</LinearGradientBrush>-->
</Border.Background>
</Border>
<ContentPresenter x:Name="contentPresenter" ContentTemplate="{TemplateBinding ContentTemplate}" Content="{TemplateBinding Content}" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}">
<ContentPresenter.Effect>
<DropShadowEffect BlurRadius="3" ShadowDepth="2" Opacity="0.5"/>
</ContentPresenter.Effect>
</ContentPresenter>
<Rectangle x:Name="DisabledVisualElement" Fill="#FFFFFFFF" IsHitTestVisible="false" Opacity="0"/>
<Rectangle x:Name="FocusVisualElement" IsHitTestVisible="false" Margin="1" Opacity="0" Stroke="#FF6DBDD1" StrokeThickness="1"/>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>

I have something similar, a white border appears on mouseover, the pressed visual state can be easily modified to show a darker background on button click.
<Style TargetType="Button" x:Name="ButtonStyle4">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="Button">
<Canvas Height="15" VerticalAlignment="Top" Margin="0,0,21,0">
<VisualStateManager.VisualStateGroups>
<VisualStateGroup x:Name="CommonStates">
<VisualState x:Name="Pressed"/>
<VisualState x:Name="MouseOver">
<Storyboard>
<ColorAnimation Duration="0" To="#FFFFF6F6" Storyboard.TargetProperty="(Shape.Stroke).(SolidColorBrush.Color)" Storyboard.TargetName="rectangle" d:IsOptimized="True"/>
</Storyboard>
</VisualState>
<VisualState x:Name="Normal"/>
<VisualState x:Name="Disabled"/>
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
<Rectangle x:Name="rectangle" Stroke="{StaticResource MenuBarBackground}" Width="84" Height="25">
<Rectangle.OpacityMask>
<RadialGradientBrush>
<GradientStop Color="Black" Offset="0"/>
<GradientStop Color="White" Offset="1"/>
</RadialGradientBrush>
</Rectangle.OpacityMask>
</Rectangle>
<TextBlock x:Name="UnderlineTextBlock" Text="Manage Apps" Margin="2,0,21,0" TextDecorations="Underline"/>
<!--<ContentPresenter Name="btnManageApps" Height="25" Width="170" RenderTransformOrigin="0.5,1.367" Content="Manage Apps"/>-->
</Canvas>
</ControlTemplate>
</Setter.Value>
</Setter>
<Setter Property="Foreground" Value="{StaticResource MenuBarButtonTextColour}"/>
</Style>
Hope this helps!

I have something similar.
The problem you were having with "Cannot resolve TargetName BorderBrush" is because you don't have an element named BorderBrush. The TargetName should refer to the name of an element, not a property name.
This is example is pretty basic and just changes one property of one element ...
<Style x:Key="ButtonStyle" TargetType="Button">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="Button">
<Grid Height="24" MinHeight="24" MaxHeight="24">
<VisualStateManager.VisualStateGroups>
<VisualStateGroup x:Name="CommonStates">
<VisualStateGroup.Transitions>
<VisualTransition GeneratedDuration="0:0:0.1"/>
</VisualStateGroup.Transitions>
<VisualState x:Name="Disabled"/>
<VisualState x:Name="Normal"/>
<VisualState x:Name="MouseOver">
<Storyboard>
<DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="rectangle" />
</Storyboard>
</VisualState>
<VisualState x:Name="Pressed">
<Storyboard>
<DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="rectangle" />
</Storyboard>
</VisualState>
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
<Rectangle x:Name="rectangle" Margin="0" StrokeThickness="0" RadiusX="5" RadiusY="5" Height="24" MinHeight="24" MaxHeight="24" Opacity="0">
<Rectangle.Fill>
<LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
<GradientStop Color="#FF00A4CB" Offset="0"/>
<GradientStop Color="#FF006BA2" Offset="0.991"/>
</LinearGradientBrush>
</Rectangle.Fill>
</Rectangle>
<TextBlock x:Name="textBlock" Margin="10,5,10,6" TextWrapping="Wrap" Text="{TemplateBinding Content}" Foreground="White" HorizontalAlignment="Center"/>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
This changes the opacity property, of the element named 'rectangle' to 1 when the button receives a mouseover or pressed event.
Within the ControlTemplate just add whatever elements you want (give them a name) and then hook up the events to change the properties on those elements. .

If you want to animate the border thickness of the Background element, try this:
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="Background" Storyboard.TargetProperty="(Border.BorderThickness)">
<DiscreteObjectKeyFrame KeyTime="00:00:00">
<DiscreteObjectKeyFrame.Value>
<Thickness>0</Thickness>
</DiscreteObjectKeyFrame.Value>
</DiscreteObjectKeyFrame>
</ObjectAnimationUsingKeyFrames>

WP - AutoCompleteBox get list of items with bigger font size

This is my code fo ACB:
<toolkit:AutoCompleteBox x:Name="acbAddress" VerticalAlignment="Top"
ItemsSource="{Binding Source={StaticResource autoCompleteWordList}, Path=ListOfAddresses}"
TextChanged="acbAddress_TextChanged" KeyUp="acbAddress_KeyUp"
Style="{StaticResource AutoCompleteBoxStyle1}"
SelectionChanged="AcbAddress_OnSelectionChanged"/>
And I found this to get Text_OnSelectionChanged working for my cursor to set right position. But now I have popup with very little font size. How can I now set font size for items in popup?
<ControlTemplate x:Key="CommonValidationToolTipTemplate" TargetType="ToolTip">
<Grid x:Name="Root" Margin="5,0" Opacity="0" RenderTransformOrigin="0,0">
<Grid.RenderTransform>
<TranslateTransform x:Name="Translation" X="-25"/>
</Grid.RenderTransform>
<VisualStateManager.VisualStateGroups>
<VisualStateGroup x:Name="OpenStates">
<VisualStateGroup.Transitions>
<VisualTransition GeneratedDuration="0"/>
<VisualTransition GeneratedDuration="0:0:0.2" To="Open">
<Storyboard>
<DoubleAnimation Duration="0:0:0.2" To="0" Storyboard.TargetProperty="X" Storyboard.TargetName="Translation">
<DoubleAnimation.EasingFunction>
<BackEase Amplitude=".3" EasingMode="EaseOut"/>
</DoubleAnimation.EasingFunction>
</DoubleAnimation>
<DoubleAnimation Duration="0:0:0.2" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="Root"/>
</Storyboard>
</VisualTransition>
</VisualStateGroup.Transitions>
<VisualState x:Name="Closed">
<Storyboard>
<DoubleAnimation Duration="0" To="0" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="Root"/>
</Storyboard>
</VisualState>
<VisualState x:Name="Open">
<Storyboard>
<DoubleAnimation Duration="0" To="0" Storyboard.TargetProperty="X" Storyboard.TargetName="Translation"/>
<DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="Root"/>
</Storyboard>
</VisualState>
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
<Border Background="#052A2E31" CornerRadius="5" Margin="4,4,-4,-4"/>
<Border Background="#152A2E31" CornerRadius="4" Margin="3,3,-3,-3"/>
<Border Background="#252A2E31" CornerRadius="3" Margin="2,2,-2,-2"/>
<Border Background="#352A2E31" CornerRadius="2" Margin="1,1,-1,-1"/>
<Border Background="#FFDC000C" CornerRadius="2">
<TextBlock Foreground="White" MaxWidth="250" Margin="8,4,8,4" TextWrapping="Wrap" Text="{Binding (Validation.Errors)[0].ErrorContent}" UseLayoutRounding="false"/>
</Border>
</Grid>
</ControlTemplate>
<Style x:Key="AutoCompleteBoxStyle1" TargetType="toolkit:AutoCompleteBox">
<Setter Property="IsTabStop" Value="False"/>
<Setter Property="Padding" Value="2"/>
<Setter Property="BorderThickness" Value="1"/>
<Setter Property="BorderBrush">
<Setter.Value>
<LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
<GradientStop Color="#FFA3AEB9" Offset="0"/>
<GradientStop Color="#FF8399A9" Offset="0.375"/>
<GradientStop Color="#FF718597" Offset="0.375"/>
<GradientStop Color="#FF617584" Offset="1"/>
</LinearGradientBrush>
</Setter.Value>
</Setter>
<Setter Property="Background" Value="#FFFFFFFF"/>
<Setter Property="Foreground" Value="#FF000000"/>
<Setter Property="MinWidth" Value="45"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="toolkit:AutoCompleteBox">
<Grid Opacity="{TemplateBinding Opacity}">
<VisualStateManager.VisualStateGroups>
<VisualStateGroup x:Name="PopupStates">
<VisualStateGroup.Transitions>
<VisualTransition GeneratedDuration="0:0:0.1" To="PopupOpened"/>
<VisualTransition GeneratedDuration="0:0:0.2" To="PopupClosed"/>
</VisualStateGroup.Transitions>
<VisualState x:Name="PopupOpened">
<Storyboard>
<DoubleAnimation To="1.0" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="PopupBorder"/>
</Storyboard>
</VisualState>
<VisualState x:Name="PopupClosed">
<Storyboard>
<DoubleAnimation To="0.0" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="PopupBorder"/>
</Storyboard>
</VisualState>
</VisualStateGroup>
<VisualStateGroup x:Name="ValidationStates">
<VisualState x:Name="Valid"/>
<VisualState x:Name="InvalidUnfocused">
<Storyboard>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Visibility" Storyboard.TargetName="ValidationErrorElement">
<DiscreteObjectKeyFrame KeyTime="0">
<DiscreteObjectKeyFrame.Value>
<Visibility>Visible</Visibility>
</DiscreteObjectKeyFrame.Value>
</DiscreteObjectKeyFrame>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
<VisualState x:Name="InvalidFocused">
<Storyboard>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Visibility" Storyboard.TargetName="ValidationErrorElement">
<DiscreteObjectKeyFrame KeyTime="0">
<DiscreteObjectKeyFrame.Value>
<Visibility>Visible</Visibility>
</DiscreteObjectKeyFrame.Value>
</DiscreteObjectKeyFrame>
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="IsOpen" Storyboard.TargetName="validationTooltip">
<DiscreteObjectKeyFrame KeyTime="0">
<DiscreteObjectKeyFrame.Value>
<System:Boolean>True</System:Boolean>
</DiscreteObjectKeyFrame.Value>
</DiscreteObjectKeyFrame>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
<TextBox x:Name="Text" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" Foreground="{TemplateBinding Foreground}" IsTabStop="True" Margin="0" Padding="{TemplateBinding Padding}" Style="{TemplateBinding TextBoxStyle}" SelectionChanged="Text_OnSelectionChanged"/>
<Border x:Name="ValidationErrorElement" BorderBrush="#FFDB000C" BorderThickness="1" CornerRadius="1" Visibility="Collapsed">
<ToolTipService.ToolTip>
<ToolTip x:Name="validationTooltip" DataContext="{Binding RelativeSource={RelativeSource TemplatedParent}}" Placement="Right" PlacementTarget="{Binding RelativeSource={RelativeSource TemplatedParent}}" Template="{StaticResource CommonValidationToolTipTemplate}">
<ToolTip.Triggers>
<EventTrigger RoutedEvent="Canvas.Loaded">
<BeginStoryboard>
<Storyboard>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="IsHitTestVisible" Storyboard.TargetName="validationTooltip">
<DiscreteObjectKeyFrame KeyTime="0">
<DiscreteObjectKeyFrame.Value>
<System:Boolean>true</System:Boolean>
</DiscreteObjectKeyFrame.Value>
</DiscreteObjectKeyFrame>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</BeginStoryboard>
</EventTrigger>
</ToolTip.Triggers>
</ToolTip>
</ToolTipService.ToolTip>
<Grid Background="Transparent" HorizontalAlignment="Right" Height="12" Margin="1,-4,-4,0" VerticalAlignment="Top" Width="12">
<Path Data="M 1,0 L6,0 A 2,2 90 0 1 8,2 L8,7 z" Fill="#FFDC000C" Margin="1,3,0,0"/>
<Path Data="M 0,0 L2,0 L 8,6 L8,8" Fill="#ffffff" Margin="1,3,0,0"/>
</Grid>
</Border>
<Popup x:Name="Popup">
<Grid Opacity="{TemplateBinding Opacity}">
<Border x:Name="PopupBorder" BorderThickness="0" Background="#11000000" HorizontalAlignment="Stretch" Opacity="0">
<Border.RenderTransform>
<TranslateTransform X="1" Y="1"/>
</Border.RenderTransform>
<Border BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" CornerRadius="0" HorizontalAlignment="Stretch" Opacity="1.0" Padding="0">
<Border.Background>
<LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
<GradientStop Color="#FFDDDDDD" Offset="0"/>
<GradientStop Color="#AADDDDDD" Offset="1"/>
</LinearGradientBrush>
</Border.Background>
<Border.RenderTransform>
<TransformGroup>
<TranslateTransform X="-1" Y="-1"/>
</TransformGroup>
</Border.RenderTransform>
<ListBox x:Name="Selector" BorderThickness="0" Background="{TemplateBinding Background}" Foreground="{TemplateBinding Foreground}" ScrollViewer.HorizontalScrollBarVisibility="Auto" ItemTemplate="{TemplateBinding ItemTemplate}" ItemContainerStyle="{TemplateBinding ItemContainerStyle}" ScrollViewer.VerticalScrollBarVisibility="Auto"/>
</Border>
</Border>
</Grid>
</Popup>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
Thanks

You should be able to just give a custom Item style via ItemContainerStyle by targeting the ListBoxItem like;
<Style x:Key="myItemStyle" TargetType="ListBoxItem">
<Setter Property="Background" Value="Khaki" />
<Setter Property="Foreground" Value="DarkSlateGray" />
<Setter Property="Margin" Value="5" />
<Setter Property="FontStyle" Value="Italic" />
<Setter Property="FontSize" Value="14" /><!-- Your Property -->
<Setter Property="BorderBrush" Value="DarkGray" />
</Style>
<toolkit:AutoCompleteBox ItemContainerStyle="{StaticResource myItemStyle}" />
You could also use BasedOn to inherit the rest of the existing style stuff from the default template into your Style so you would only be changing the FontSize
More detailed info found here
Hope this helps.

How does the Silverlight combobox disappear the way it does?

In silverlight if I expand a combobox and then move the mouse cursor away, no matter where I click on the silverlight app the combobox dropdown collapses again. How does it do this and can I replicate it myself?

In Silverlight, this is done with states in the VisualStateManager (VSM for short).
Silverlight Introduces the VSM
And here is template for ComboBox that you can use to see how it works with the VSM to make that happen and play around with it:
<Style TargetType="ComboBox">
<Setter Property="Padding" Value="6,2,25,2"/>
<Setter Property="Background" Value="#FF1F3B53"/>
<Setter Property="HorizontalContentAlignment" Value="Left"/>
<Setter Property="BorderThickness" Value="1"/>
<Setter Property="TabNavigation" Value="Once"/>
<Setter Property="ScrollViewer.HorizontalScrollBarVisibility" Value="Auto"/>
<Setter Property="ScrollViewer.VerticalScrollBarVisibility" Value="Auto"/>
<Setter Property="BorderBrush">
<Setter.Value>
<LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
<GradientStop Color="#FFA3AEB9" Offset="0"/>
<GradientStop Color="#FF8399A9" Offset="0.375"/>
<GradientStop Color="#FF718597" Offset="0.375"/>
<GradientStop Color="#FF617584" Offset="1"/>
</LinearGradientBrush>
</Setter.Value>
</Setter>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="ComboBox">
<Grid>
<Grid.Resources>
<Style x:Name="comboToggleStyle" TargetType="ToggleButton">
<Setter Property="Foreground" Value="#FF333333"/>
<Setter Property="Background" Value="#FF1F3B53"/>
<Setter Property="BorderBrush">
<Setter.Value>
<LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
<GradientStop Color="#FFA3AEB9" Offset="0"/>
<GradientStop Color="#FF8399A9" Offset="0.375"/>
<GradientStop Color="#FF718597" Offset="0.375"/>
<GradientStop Color="#FF617584" Offset="1"/>
</LinearGradientBrush>
</Setter.Value>
</Setter>
<Setter Property="BorderThickness" Value="1"/>
<Setter Property="Padding" Value="3"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="ToggleButton">
<Grid>
<VisualStateManager.VisualStateGroups>
<VisualStateGroup x:Name="CommonStates">
<VisualState x:Name="Normal"/>
<VisualState x:Name="MouseOver">
<Storyboard>
<DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="BackgroundOverlay"/>
<ColorAnimation Duration="0" To="#7FFFFFFF" Storyboard.TargetProperty="(Shape.Fill).(GradientBrush.GradientStops)[3].(GradientStop.Color)" Storyboard.TargetName="BackgroundGradient"/>
<ColorAnimation Duration="0" To="#CCFFFFFF" Storyboard.TargetProperty="(Shape.Fill).(GradientBrush.GradientStops)[2].(GradientStop.Color)" Storyboard.TargetName="BackgroundGradient"/>
<ColorAnimation Duration="0" To="#F2FFFFFF" Storyboard.TargetProperty="(Shape.Fill).(GradientBrush.GradientStops)[1].(GradientStop.Color)" Storyboard.TargetName="BackgroundGradient"/>
</Storyboard>
</VisualState>
<VisualState x:Name="Pressed">
<Storyboard>
<DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="BackgroundOverlay2"/>
<DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="(UIElement.Opacity)" Storyboard.TargetName="Highlight"/>
<ColorAnimation Duration="0" To="#E5FFFFFF" Storyboard.TargetProperty="(Shape.Fill).(GradientBrush.GradientStops)[1].(GradientStop.Color)" Storyboard.TargetName="BackgroundGradient"/>
<ColorAnimation Duration="0" To="#BCFFFFFF" Storyboard.TargetProperty="(Shape.Fill).(GradientBrush.GradientStops)[2].(GradientStop.Color)" Storyboard.TargetName="BackgroundGradient"/>
<ColorAnimation Duration="0" To="#6BFFFFFF" Storyboard.TargetProperty="(Shape.Fill).(GradientBrush.GradientStops)[3].(GradientStop.Color)" Storyboard.TargetName="BackgroundGradient"/>
<ColorAnimation Duration="0" To="#F2FFFFFF" Storyboard.TargetProperty="(Shape.Fill).(GradientBrush.GradientStops)[0].(GradientStop.Color)" Storyboard.TargetName="BackgroundGradient"/>
</Storyboard>
</VisualState>
<VisualState x:Name="Disabled"/>
</VisualStateGroup>
<VisualStateGroup x:Name="CheckStates">
<VisualState x:Name="Checked">
<Storyboard>
<DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="(UIElement.Opacity)" Storyboard.TargetName="BackgroundOverlay3"/>
<DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="(UIElement.Opacity)" Storyboard.TargetName="Highlight"/>
<DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="(UIElement.Opacity)" Storyboard.TargetName="BackgroundGradient2"/>
<ColorAnimation Duration="0" To="#E5FFFFFF" Storyboard.TargetProperty="(Shape.Fill).(GradientBrush.GradientStops)[1].(GradientStop.Color)" Storyboard.TargetName="BackgroundGradient2"/>
<ColorAnimation Duration="0" To="#BCFFFFFF" Storyboard.TargetProperty="(Shape.Fill).(GradientBrush.GradientStops)[2].(GradientStop.Color)" Storyboard.TargetName="BackgroundGradient2"/>
<ColorAnimation Duration="0" To="#6BFFFFFF" Storyboard.TargetProperty="(Shape.Fill).(GradientBrush.GradientStops)[3].(GradientStop.Color)" Storyboard.TargetName="BackgroundGradient2"/>
<ColorAnimation Duration="0" To="#F2FFFFFF" Storyboard.TargetProperty="(Shape.Fill).(GradientBrush.GradientStops)[0].(GradientStop.Color)" Storyboard.TargetName="BackgroundGradient2"/>
</Storyboard>
</VisualState>
<VisualState x:Name="Unchecked"/>
</VisualStateGroup>
<VisualStateGroup x:Name="FocusStates">
<VisualState x:Name="Focused">
<Storyboard>
<ObjectAnimationUsingKeyFrames Duration="0" Storyboard.TargetProperty="Visibility" Storyboard.TargetName="FocusVisualElement">
<DiscreteObjectKeyFrame KeyTime="0">
<DiscreteObjectKeyFrame.Value>
<Visibility>Visible</Visibility>
</DiscreteObjectKeyFrame.Value>
</DiscreteObjectKeyFrame>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
<VisualState x:Name="Unfocused"/>
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
<Rectangle x:Name="Background" Fill="{TemplateBinding Background}" RadiusY="3" RadiusX="3" Stroke="{TemplateBinding BorderBrush}" StrokeThickness="{TemplateBinding BorderThickness}"/>
<Rectangle x:Name="BackgroundOverlay" Fill="#FF448DCA" Opacity="0" RadiusY="3" RadiusX="3" Stroke="#00000000" StrokeThickness="{TemplateBinding BorderThickness}"/>
<Rectangle x:Name="BackgroundOverlay2" Fill="#FF448DCA" Opacity="0" RadiusY="3" RadiusX="3" Stroke="#00000000" StrokeThickness="{TemplateBinding BorderThickness}"/>
<Rectangle x:Name="BackgroundGradient" Margin="{TemplateBinding BorderThickness}" RadiusY="2" RadiusX="2" Stroke="#FFFFFFFF" StrokeThickness="1">
<Rectangle.Fill>
<LinearGradientBrush EndPoint=".7,1" StartPoint=".7,0">
<GradientStop Color="#FFFFFFFF" Offset="0"/>
<GradientStop Color="#F9FFFFFF" Offset="0.375"/>
<GradientStop Color="#E5FFFFFF" Offset="0.625"/>
<GradientStop Color="#C6FFFFFF" Offset="1"/>
</LinearGradientBrush>
</Rectangle.Fill>
</Rectangle>
<Rectangle x:Name="BackgroundOverlay3" Fill="#FF448DCA" Opacity="0" RadiusY="3" RadiusX="3" Stroke="#00000000" StrokeThickness="{TemplateBinding BorderThickness}"/>
<Rectangle x:Name="BackgroundGradient2" Margin="{TemplateBinding BorderThickness}" Opacity="0" RadiusY="2" RadiusX="2" Stroke="#FFFFFFFF" StrokeThickness="1">
<Rectangle.Fill>
<LinearGradientBrush EndPoint=".7,1" StartPoint=".7,0">
<GradientStop Color="#FFFFFFFF" Offset="0"/>
<GradientStop Color="#F9FFFFFF" Offset="0.375"/>
<GradientStop Color="#E5FFFFFF" Offset="0.625"/>
<GradientStop Color="#C6FFFFFF" Offset="1"/>
</LinearGradientBrush>
</Rectangle.Fill>
</Rectangle>
<Rectangle x:Name="Highlight" IsHitTestVisible="false" Margin="{TemplateBinding BorderThickness}" Opacity="0" RadiusY="2" RadiusX="2" Stroke="#FF6DBDD1" StrokeThickness="1"/>
<ContentPresenter x:Name="contentPresenter" ContentTemplate="{TemplateBinding ContentTemplate}" Content="{TemplateBinding Content}" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
<Rectangle x:Name="FocusVisualElement" IsHitTestVisible="false" Margin="1" RadiusY="3.5" RadiusX="3.5" Stroke="#FF6DBDD1" StrokeThickness="1" Visibility="Collapsed"/>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</Grid.Resources>
<VisualStateManager.VisualStateGroups>
<VisualStateGroup x:Name="CommonStates">
<VisualState x:Name="Normal"/>
<VisualState x:Name="MouseOver"/>
<VisualState x:Name="Disabled">
<Storyboard>
<DoubleAnimation Duration="00:00:00" To=".55" Storyboard.TargetProperty="(UIElement.Opacity)" Storyboard.TargetName="DisabledVisualElement"/>
</Storyboard>
</VisualState>
</VisualStateGroup>
<VisualStateGroup x:Name="FocusStates">
<VisualState x:Name="Focused">
<Storyboard>
<DoubleAnimation Duration="00:00:00" To="1" Storyboard.TargetProperty="(UIElement.Opacity)" Storyboard.TargetName="FocusVisualElement"/>
</Storyboard>
</VisualState>
<VisualState x:Name="Unfocused"/>
<VisualState x:Name="FocusedDropDown">
<Storyboard>
<ObjectAnimationUsingKeyFrames Duration="00:00:00" Storyboard.TargetProperty="(UIElement.Visibility)" Storyboard.TargetName="PopupBorder">
<DiscreteObjectKeyFrame KeyTime="00:00:00">
<DiscreteObjectKeyFrame.Value>
<Visibility>Visible</Visibility>
</DiscreteObjectKeyFrame.Value>
</DiscreteObjectKeyFrame>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
</VisualStateGroup>
<VisualStateGroup x:Name="ValidationStates">
<VisualState x:Name="Valid"/>
<VisualState x:Name="InvalidUnfocused">
<Storyboard>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Visibility" Storyboard.TargetName="ValidationErrorElement">
<DiscreteObjectKeyFrame KeyTime="0">
<DiscreteObjectKeyFrame.Value>
<Visibility>Visible</Visibility>
</DiscreteObjectKeyFrame.Value>
</DiscreteObjectKeyFrame>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
<VisualState x:Name="InvalidFocused">
<Storyboard>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Visibility" Storyboard.TargetName="ValidationErrorElement">
<DiscreteObjectKeyFrame KeyTime="0">
<DiscreteObjectKeyFrame.Value>
<Visibility>Visible</Visibility>
</DiscreteObjectKeyFrame.Value>
</DiscreteObjectKeyFrame>
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="IsOpen" Storyboard.TargetName="validationTooltip">
<DiscreteObjectKeyFrame KeyTime="0">
<DiscreteObjectKeyFrame.Value>
<System:Boolean>True</System:Boolean>
</DiscreteObjectKeyFrame.Value>
</DiscreteObjectKeyFrame>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
<Border x:Name="ContentPresenterBorder">
<Grid>
<ToggleButton x:Name="DropDownToggle" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" HorizontalAlignment="Stretch" HorizontalContentAlignment="Right" Margin="0" Style="{StaticResource comboToggleStyle}" VerticalAlignment="Stretch">
<Path x:Name="BtnArrow" Data="F1 M 301.14,-189.041L 311.57,-189.041L 306.355,-182.942L 301.14,-189.041 Z " HorizontalAlignment="Right" Height="4" Margin="0,0,6,0" Stretch="Uniform" Width="8">
<Path.Fill>
<SolidColorBrush x:Name="BtnArrowColor" Color="#FF333333"/>
</Path.Fill>
</Path>
</ToggleButton>
<ContentPresenter x:Name="ContentPresenter" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}">
<TextBlock Text=" "/>
</ContentPresenter>
</Grid>
</Border>
<Rectangle x:Name="DisabledVisualElement" Fill="White" IsHitTestVisible="false" Opacity="0" RadiusY="3" RadiusX="3"/>
<Rectangle x:Name="FocusVisualElement" IsHitTestVisible="false" Margin="1" Opacity="0" RadiusY="2" RadiusX="2" Stroke="#FF6DBDD1" StrokeThickness="1"/>
<Border x:Name="ValidationErrorElement" BorderBrush="#FFDB000C" BorderThickness="1" CornerRadius="1" Visibility="Collapsed">
<ToolTipService.ToolTip>
<ToolTip x:Name="validationTooltip" DataContext="{Binding RelativeSource={RelativeSource TemplatedParent}}" Placement="Right" PlacementTarget="{Binding RelativeSource={RelativeSource TemplatedParent}}" Template="{StaticResource ValidationToolTipTemplate}">
<ToolTip.Triggers>
<EventTrigger RoutedEvent="Canvas.Loaded">
<BeginStoryboard>
<Storyboard>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="IsHitTestVisible" Storyboard.TargetName="validationTooltip">
<DiscreteObjectKeyFrame KeyTime="0">
<DiscreteObjectKeyFrame.Value>
<System:Boolean>true</System:Boolean>
</DiscreteObjectKeyFrame.Value>
</DiscreteObjectKeyFrame>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</BeginStoryboard>
</EventTrigger>
</ToolTip.Triggers>
</ToolTip>
</ToolTipService.ToolTip>
<Grid Background="Transparent" HorizontalAlignment="Right" Height="12" Margin="1,-4,-4,0" VerticalAlignment="Top" Width="12">
<Path Data="M 1,0 L6,0 A 2,2 90 0 1 8,2 L8,7 z" Fill="#FFDC000C" Margin="1,3,0,0"/>
<Path Data="M 0,0 L2,0 L 8,6 L8,8" Fill="#ffffff" Margin="1,3,0,0"/>
</Grid>
</Border>
<Popup x:Name="Popup">
<Border x:Name="PopupBorder" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" CornerRadius="3" HorizontalAlignment="Stretch" Height="Auto">
<Border.Background>
<LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
<GradientStop Color="#FFFFFFFF" Offset="0"/>
<GradientStop Color="#FFFEFEFE" Offset="1"/>
</LinearGradientBrush>
</Border.Background>
<ScrollViewer x:Name="ScrollViewer" BorderThickness="0" Padding="1">
<ItemsPresenter/>
</ScrollViewer>
</Border>
</Popup>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>

If you have Expression Blend, you can easily find out how it's done.
Simply create a SL project, add a ComboBox ot the surface, Right-Click it and select Edit Template->Make a Copy, then inspect the template, it's probably made with some animation on one of the transitions / Visual State Manager.

The key is that the control's template uses a Popup control, which you can use yourself in your own controls.
http://msdn.microsoft.com/en-us/library/system.windows.controls.primitives.popup%28v=VS.95%29.aspx

How to Begin a StoryBoard from ViewModel?

I am utilizing Telerik controls in my example.
<telerik:RadPanelBarItem Collapsed="RadPanelBarItem_Collapsed"
DropPosition="Inside"
Header="Searching for Clients"
IsExpanded="false"
IsTabStop="True"
TabNavigation="Once">
<i:Interaction.Triggers>
<i:EventTrigger EventName="Expanded">
<i:InvokeCommandAction Command="{Binding ExpandedComand}" />
</i:EventTrigger>
</i:Interaction.Triggers>
</telerik:RadPanelBarItem>
I would like to Run code within the ViewModel whenever the Expanded event is triggered. So far so good, but I also need to start an animation upon expanding it. But this is not possible from the ViewModel, but it has to run on the view:
ArrowStoryboard.Begin();
So how should I do this?
UPDATE:
Let me elaborate a bit more as it seems it caused some confusion. I don't have to execute the view related animation from the ViewModel. But I have to execute two thing upon expansion event. 1) Begin the Animation and 2) run a set of code on the viewModel.
The only way I know of but isn't great as it ads code to the code-behind is this:
Casting the DataContext to the ViewModel and run the according method on the ViewModel right after beginning of Animation.
Thanks,

Why not attach another behavior ControlStoryboardAction aside your InvokeCommandAction?
xmlns:eim="clr-namespace:Microsoft.Expression.Interactivity.Media;assembly=Microsoft.Expression.Interactions"
<i:Interaction.Triggers>
<i:EventTrigger EventName="Expanded">
<i:InvokeCommandAction Command="{Binding ExpandedComand}" />
<eim:ControlStoryboardAction Storyboard="{StaticResource YourStoryBoard}"/>
</i:EventTrigger>
</i:Interaction.Triggers>
UPDATE
It's actually not a lot of work to do this kind of animations inside the style using Blend.
What I've done here basically is I used Blend to generate the default style of RadPanelBarItem, then in the Expand visual state, I created an animation that flys out the arrow and made it run forever.
This is not exactly the animation you want (the arrow goes up rather than right) but it may give you some ideas. Hope this helps. :)
Just apply the style name AnimatedRadPanelBarItemStyle.
<LinearGradientBrush x:Key="ControlItem_Background_Normal" EndPoint="0.5,1" StartPoint="0.5,0">
<GradientStop Color="White"/>
<GradientStop Color="Gainsboro" Offset="0.43"/>
<GradientStop Color="#FFADADAD" Offset="0.44"/>
<GradientStop Color="#FFD4D4D4" Offset="1"/>
</LinearGradientBrush>
<SolidColorBrush x:Key="ControlItem_OuterBorder_Normal" Color="#FF848484"/>
<SolidColorBrush x:Key="ControlForeground_Normal" Color="#FF000000"/>
<SolidColorBrush x:Key="ControlItem_InnerBorder_Normal" Color="#FFFFFFFF"/>
<SolidColorBrush x:Key="ControlItem_OuterBorder_MouseOver" Color="#FFFFC92B"/>
<SolidColorBrush x:Key="ControlItem_InnerBorder_MouseOver" Color="#FFFFFFFF"/>
<LinearGradientBrush x:Key="ControlItem_Background_MouseOver" EndPoint="0.5,1" StartPoint="0.5,0">
<GradientStop Color="#FFFFFBA3" Offset="1"/>
<GradientStop Color="#FFFFFBDA" Offset="0"/>
<GradientStop Color="#FFFFD25A" Offset="0.43"/>
<GradientStop Color="#FFFEEBAE" Offset="0.42"/>
</LinearGradientBrush>
<LinearGradientBrush x:Key="ControlItem_OuterBorder_Selected" EndPoint="0.5,1" StartPoint="0.5,0">
<GradientStop Color="#FF282828"/>
<GradientStop Color="#FF5F5F5F" Offset="1"/>
</LinearGradientBrush>
<LinearGradientBrush x:Key="ControlItem_InnerBorder_Selected" EndPoint="0.5,1" StartPoint="0.5,0">
<GradientStop Color="#FFB69A78"/>
<GradientStop Color="#FFFFE17A" Offset="0.126"/>
</LinearGradientBrush>
<LinearGradientBrush x:Key="ControlItem_Background_Selected" EndPoint="0.5,1" StartPoint="0.5,0">
<GradientStop Color="#FFFFD74E" Offset="0.996"/>
<GradientStop Color="#FFFFDCAB" Offset="0.17"/>
<GradientStop Color="#FFFFB062" Offset="0.57"/>
<GradientStop Color="#FFFFD18F" Offset="0.56"/>
<GradientStop Color="#FFFFBA74"/>
</LinearGradientBrush>
<SolidColorBrush x:Key="ControlOuterBorder_Disabled" Color="#FF989898"/>
<SolidColorBrush x:Key="ControlInnerBorder_Disabled" Color="Transparent"/>
<SolidColorBrush x:Key="ControlBackground_Disabled" Color="#FFE0E0E0"/>
<SolidColorBrush x:Key="ControlElement_Normal" Color="#FF000000"/>
<SolidColorBrush x:Key="FocusBrushBlack" Color="#FF000000"/>
<ControlTemplate x:Key="PanelBarItemTopLevelTemplate" TargetType="telerik:RadPanelBarItem">
<Grid x:Name="RootElement">
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<VisualStateManager.VisualStateGroups>
<VisualStateGroup x:Name="CommonStates">
<VisualState x:Name="Normal"/>
<VisualState x:Name="Disabled">
<Storyboard>
<DoubleAnimation Duration="0" To="0" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="NormalVisual"/>
<DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="DisabledVisual"/>
<DoubleAnimation Duration="0" To="0.5" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="Header"/>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Visibility)" Storyboard.TargetName="arrow">
<DiscreteObjectKeyFrame KeyTime="0">
<DiscreteObjectKeyFrame.Value>
<Visibility>Collapsed</Visibility>
</DiscreteObjectKeyFrame.Value>
</DiscreteObjectKeyFrame>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
<VisualState x:Name="MouseOver">
<Storyboard>
<DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="MouseOverVisual"/>
</Storyboard>
</VisualState>
<VisualState x:Name="MouseOut"/>
</VisualStateGroup>
<VisualStateGroup x:Name="SelectionStates">
<VisualState x:Name="Unselected"/>
<VisualState x:Name="Selected">
<Storyboard>
<DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="SelectVisual"/>
</Storyboard>
</VisualState>
</VisualStateGroup>
<VisualStateGroup x:Name="ExpandStates">
<VisualState x:Name="Expanded">
<Storyboard RepeatBehavior="Forever">
<ObjectAnimationUsingKeyFrames Duration="0" Storyboard.TargetProperty="Visibility" Storyboard.TargetName="ItemsContainer">
<DiscreteObjectKeyFrame KeyTime="0" Value="Visible"/>
</ObjectAnimationUsingKeyFrames>
<DoubleAnimation Duration="0:0:0.2" From="0.0" To="1.0" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="ItemsContainer"/>
<DoubleAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.RenderTransform).(CompositeTransform.TranslateY)" Storyboard.TargetName="arrow">
<EasingDoubleKeyFrame KeyTime="0:0:1" Value="-6"/>
<EasingDoubleKeyFrame KeyTime="0:0:1.2" Value="0"/>
<EasingDoubleKeyFrame KeyTime="0:0:1.4" Value="0"/>
</DoubleAnimationUsingKeyFrames>
<DoubleAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.RenderTransform).(CompositeTransform.Rotation)" Storyboard.TargetName="arrow">
<EasingDoubleKeyFrame KeyTime="0" Value="180"/>
<EasingDoubleKeyFrame KeyTime="0:0:1" Value="180"/>
<EasingDoubleKeyFrame KeyTime="0:0:1.2" Value="180"/>
<EasingDoubleKeyFrame KeyTime="0:0:1.4" Value="180"/>
</DoubleAnimationUsingKeyFrames>
<DoubleAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Opacity)" Storyboard.TargetName="arrow">
<EasingDoubleKeyFrame KeyTime="0" Value="1"/>
<EasingDoubleKeyFrame KeyTime="0:0:1" Value="0"/>
<EasingDoubleKeyFrame KeyTime="0:0:1.2" Value="0"/>
<EasingDoubleKeyFrame KeyTime="0:0:1.4" Value="1"/>
</DoubleAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
<VisualState x:Name="Collapsed"/>
</VisualStateGroup>
<VisualStateGroup x:Name="FocusStates">
<VisualState x:Name="Focused">
<Storyboard>
<ObjectAnimationUsingKeyFrames Duration="0" Storyboard.TargetProperty="Visibility" Storyboard.TargetName="FocusVisual">
<DiscreteObjectKeyFrame KeyTime="0" Value="Visible"/>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
<VisualState x:Name="Unfocused">
<Storyboard>
<ObjectAnimationUsingKeyFrames Duration="0" Storyboard.TargetProperty="Visibility" Storyboard.TargetName="FocusVisual">
<DiscreteObjectKeyFrame KeyTime="0" Value="Collapsed"/>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
<Grid x:Name="HeaderRow">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<Border x:Name="NormalVisual" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Grid.ColumnSpan="5">
<Border BorderBrush="{StaticResource ControlItem_InnerBorder_Normal}" BorderThickness="1" Background="{TemplateBinding Background}"/>
</Border>
<Border x:Name="MouseOverVisual" BorderBrush="{StaticResource ControlItem_OuterBorder_MouseOver}" BorderThickness="1" Grid.ColumnSpan="5" Opacity="0">
<Border BorderBrush="{StaticResource ControlItem_InnerBorder_MouseOver}" BorderThickness="1" Background="{StaticResource ControlItem_Background_MouseOver}"/>
</Border>
<Border x:Name="SelectVisual" BorderBrush="{StaticResource ControlItem_OuterBorder_Selected}" BorderThickness="1" Grid.ColumnSpan="5" Opacity="0">
<Border BorderBrush="{StaticResource ControlItem_InnerBorder_Selected}" BorderThickness="1" Background="{StaticResource ControlItem_Background_Selected}"/>
</Border>
<Border x:Name="DisabledVisual" BorderBrush="{StaticResource ControlOuterBorder_Disabled}" BorderThickness="1" Grid.ColumnSpan="5" Opacity="0">
<Border BorderBrush="{StaticResource ControlInnerBorder_Disabled}" BorderThickness="1" Background="{StaticResource ControlBackground_Disabled}"/>
</Border>
<Path x:Name="arrow" Grid.Column="5" Data="M 1,1.5 L 4.5,5 L 8,1.5" HorizontalAlignment="Right" Margin="7 0" Opacity="1" RenderTransformOrigin="0.5 0.5" Stretch="None" Stroke="{StaticResource ControlElement_Normal}" StrokeThickness="2" VerticalAlignment="Center">
<Path.RenderTransform>
<CompositeTransform Rotation="0"/>
</Path.RenderTransform>
</Path>
<ContentPresenter x:Name="Header" Grid.ColumnSpan="4" ContentTemplate="{TemplateBinding HeaderTemplate}" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
<Rectangle x:Name="FocusVisual" Grid.ColumnSpan="5" Grid.Column="0" IsHitTestVisible="False" Stroke="{StaticResource FocusBrushBlack}" StrokeThickness="1" StrokeDashArray="1 2" Visibility="Collapsed"/>
</Grid>
<Grid x:Name="ItemsContainer" Grid.Row="1" Visibility="Collapsed">
<telerik:LayoutTransformControl x:Name="transformationRoot">
<ItemsPresenter/>
</telerik:LayoutTransformControl>
</Grid>
</Grid>
</ControlTemplate>
<SolidColorBrush x:Key="ControlSubItem_OuterBorder_MouseOver" Color="#FFFFC92B"/>
<Thickness x:Key="ControlSubItem_OuterBorderThickness">1</Thickness>
<SolidColorBrush x:Key="ControlSubItem_InnerBorder_MouseOver" Color="#FFFFFFFF"/>
<Thickness x:Key="ControlSubItem_InnerBorderThickness">1</Thickness>
<LinearGradientBrush x:Key="ControlSubItem_Background_MouseOver" EndPoint="0.5,1" StartPoint="0.5,0">
<GradientStop Color="#FFFFFBA3" Offset="1"/>
<GradientStop Color="#FFFFFBDA" Offset="0"/>
</LinearGradientBrush>
<CornerRadius x:Key="ControlSubItem_InnerCornerRadius">0</CornerRadius>
<CornerRadius x:Key="ControlSubItem_OuterCornerRadius">1</CornerRadius>
<SolidColorBrush x:Key="ControlSubItem_OuterBorder_Selected" Color="#FFFFC92B"/>
<SolidColorBrush x:Key="ControlSubItem_InnerBorder_Selected" Color="#FFFFFFFF"/>
<LinearGradientBrush x:Key="ControlSubItem_Background_Selected" EndPoint="0.5,1" StartPoint="0.5,0">
<GradientStop Color="#FFFCE79F" Offset="1"/>
<GradientStop Color="#FFFDD3A8"/>
</LinearGradientBrush>
<ControlTemplate x:Key="PanelBarItemSecondLevelTemplate" TargetType="telerik:RadPanelBarItem">
<Grid x:Name="RootElement">
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<VisualStateManager.VisualStateGroups>
<VisualStateGroup x:Name="CommonStates">
<VisualState x:Name="Normal"/>
<VisualState x:Name="Disabled">
<Storyboard>
<DoubleAnimation Duration="0" To="1.0" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="DisabledVisual"/>
</Storyboard>
</VisualState>
<VisualState x:Name="MouseOver">
<Storyboard>
<DoubleAnimation Duration="0:0:0.2" To="1.0" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="MouseOverVisual"/>
</Storyboard>
</VisualState>
<VisualState x:Name="MouseOut">
<Storyboard>
<DoubleAnimation Duration="0:0:0.2" To="0.0" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="MouseOverVisual"/>
</Storyboard>
</VisualState>
</VisualStateGroup>
<VisualStateGroup x:Name="SelectionStates">
<VisualState x:Name="Unselected"/>
<VisualState x:Name="Selected">
<Storyboard>
<DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="SelectionVisual"/>
</Storyboard>
</VisualState>
</VisualStateGroup>
<VisualStateGroup x:Name="ExpandStates">
<VisualState x:Name="Expanded">
<Storyboard>
<ObjectAnimationUsingKeyFrames Duration="0" Storyboard.TargetProperty="Visibility" Storyboard.TargetName="ItemsContainer">
<DiscreteObjectKeyFrame KeyTime="0" Value="Visible"/>
</ObjectAnimationUsingKeyFrames>
<DoubleAnimation Duration="0:0:0.2" From="0.0" To="1.0" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="ItemsContainer"/>
</Storyboard>
</VisualState>
<VisualState x:Name="Collapsed"/>
</VisualStateGroup>
<VisualStateGroup x:Name="FocusStates">
<VisualState x:Name="Focused">
<Storyboard>
<ObjectAnimationUsingKeyFrames Duration="0" Storyboard.TargetProperty="Visibility" Storyboard.TargetName="FocusVisual">
<DiscreteObjectKeyFrame KeyTime="0" Value="Visible"/>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
<VisualState x:Name="Unfocused">
<Storyboard>
<ObjectAnimationUsingKeyFrames Duration="0" Storyboard.TargetProperty="Visibility" Storyboard.TargetName="FocusVisual">
<DiscreteObjectKeyFrame KeyTime="0" Value="Collapsed"/>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
<Grid x:Name="HeaderRow" Background="Transparent">
<Border x:Name="MouseOverVisual" BorderBrush="{StaticResource ControlSubItem_OuterBorder_MouseOver}" BorderThickness="{StaticResource ControlSubItem_OuterBorderThickness}" CornerRadius="{StaticResource ControlSubItem_OuterCornerRadius}" Opacity="0">
<Border BorderBrush="{StaticResource ControlSubItem_InnerBorder_MouseOver}" BorderThickness="{StaticResource ControlSubItem_InnerBorderThickness}" Background="{StaticResource ControlSubItem_Background_MouseOver}" CornerRadius="{StaticResource ControlSubItem_InnerCornerRadius}"/>
</Border>
<Border x:Name="SelectionVisual" BorderBrush="{StaticResource ControlSubItem_OuterBorder_Selected}" BorderThickness="{StaticResource ControlSubItem_OuterBorderThickness}" CornerRadius="{StaticResource ControlSubItem_OuterCornerRadius}" Opacity="0">
<Border BorderBrush="{StaticResource ControlSubItem_InnerBorder_Selected}" BorderThickness="{StaticResource ControlSubItem_InnerBorderThickness}" Background="{StaticResource ControlSubItem_Background_Selected}" CornerRadius="{StaticResource ControlSubItem_InnerCornerRadius}"/>
</Border>
<Border x:Name="DisabledVisual" BorderBrush="{StaticResource ControlOuterBorder_Disabled}" BorderThickness="{StaticResource ControlSubItem_OuterBorderThickness}" CornerRadius="{StaticResource ControlSubItem_OuterCornerRadius}" Opacity="0">
<Border BorderBrush="{StaticResource ControlInnerBorder_Disabled}" BorderThickness="{StaticResource ControlSubItem_InnerBorderThickness}" Background="{StaticResource ControlBackground_Disabled}" CornerRadius="{StaticResource ControlSubItem_InnerCornerRadius}"/>
</Border>
<ContentPresenter x:Name="Header" ContentTemplate="{TemplateBinding HeaderTemplate}" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
<Rectangle x:Name="FocusVisual" IsHitTestVisible="False" RadiusY="2" RadiusX="2" Stroke="{StaticResource FocusBrushBlack}" StrokeThickness="1" StrokeDashArray="1 2" Visibility="Collapsed"/>
</Grid>
<Grid x:Name="ItemsContainer" Grid.Row="1" Visibility="Collapsed">
<ItemsPresenter/>
</Grid>
</Grid>
</ControlTemplate>
<Style x:Key="AnimatedRadPanelBarItemStyle" TargetType="telerik:RadPanelBarItem">
<Setter Property="Background" Value="{StaticResource ControlItem_Background_Normal}"/>
<Setter Property="BorderBrush" Value="{StaticResource ControlItem_OuterBorder_Normal}"/>
<Setter Property="BorderThickness" Value="1"/>
<Setter Property="Foreground" Value="{StaticResource ControlForeground_Normal}"/>
<Setter Property="TabNavigation" Value="Once"/>
<Setter Property="IsTabStop" Value="True"/>
<Setter Property="Template" Value="{StaticResource PanelBarItemTopLevelTemplate}"/>
<Setter Property="Padding" Value="3"/>
<Setter Property="HorizontalContentAlignment" Value="Stretch"/>
<Setter Property="VerticalContentAlignment" Value="Stretch"/>
<Setter Property="ChildItemsTemplate" Value="{StaticResource PanelBarItemSecondLevelTemplate}"/>
<Setter Property="ItemsPanel">
<Setter.Value>
<ItemsPanelTemplate>
<telerik:PanelBarPanel/>
</ItemsPanelTemplate>
</Setter.Value>
</Setter>
</Style>

It's a bad idea to raise view specific action from ViewModel since storyboard has nothing with view model. There're two ways to achieve what you want to do.
You can inject View into ViewModel but I really don't like this idea since MVVM try to make View and ViewModel less coupling.
Use Message Service to send and retrieve data between View and ViewModel this way they don't know each other. I adopt MVVMLight to my project and use its Messenger class. MVVMLight is very easy to use.