InvalidOperationException in VS2010 - wpf

Question

I'm using Expression Blend 4 + Visual Studio 2010 Pro to create a WPF application.
I have created an control Style (or should I say Template?) based on a CheckBox using only Blend 4, which works perfectly. However when I go to VS2010 I get the following "error":
'[Unknown]' property does not point to
a DependencyObject in path
'(0).(1)[0].(2)'.
Even though when I run the application it works perfectly fine. Now, I don't need to fix this error, but I would like to get rid of it anyway.
Here is the Style's XAML code:
<Style x:Key="IRSensorCheckBoxStyle" TargetType="{x:Type CheckBox}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type CheckBox}">
<Grid Cursor="Hand">
<VisualStateManager.VisualStateGroups>
<VisualStateGroup x:Name="CommonStates">
<VisualState x:Name="Normal">
<Storyboard>
<DoubleAnimationUsingKeyFrames Storyboard.TargetProperty="(Shape.StrokeThickness)" Storyboard.TargetName="ellipse">
<EasingDoubleKeyFrame KeyTime="0:0:0.1" Value="0"/>
</DoubleAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
<VisualState x:Name="MouseOver">
<Storyboard>
<DoubleAnimationUsingKeyFrames Storyboard.TargetProperty="(Shape.StrokeThickness)" Storyboard.TargetName="ellipse">
<EasingDoubleKeyFrame KeyTime="0:0:0.2" Value="2"/>
</DoubleAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
<VisualState x:Name="Pressed">
<Storyboard>
<DoubleAnimationUsingKeyFrames Storyboard.TargetProperty="(Shape.StrokeThickness)" Storyboard.TargetName="ellipse">
<EasingDoubleKeyFrame KeyTime="0" Value="2"/>
</DoubleAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
<VisualState x:Name="Disabled"/>
</VisualStateGroup>
<VisualStateGroup x:Name="CheckStates">
<VisualState x:Name="Checked">
<Storyboard>
<ColorAnimationUsingKeyFrames Storyboard.TargetProperty="(Shape.Fill).(GradientBrush.GradientStops)[0].(GradientStop.Color)" Storyboard.TargetName="ellipse">
<EasingColorKeyFrame KeyTime="0:0:0.3" Value="Red"/>
</ColorAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
<VisualState x:Name="Unchecked">
<Storyboard>
<ColorAnimationUsingKeyFrames Storyboard.TargetProperty="(Shape.Fill).(GradientBrush.GradientStops)[0].(GradientStop.Color)" Storyboard.TargetName="ellipse">
<EasingColorKeyFrame KeyTime="0:0:0.2" Value="#00FF0000"/>
</ColorAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
<VisualState x:Name="Indeterminate"/>
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
<Ellipse x:Name="ellipse" Stroke="Yellow" StrokeThickness="0">
<Ellipse.Fill>
<RadialGradientBrush>
<GradientStop Color="Red"/>
<GradientStop Offset="1" Color="#00FF0000"/>
</RadialGradientBrush>
</Ellipse.Fill>
</Ellipse>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
As you can see the error references to both Storyboards in the Checked and Unchecked states. However I don't agree with the error in that the property is not pointing to a DependencyObject (whatever that is...), because the Target is "ellipse" which is there; and the Target Property is pointing to a Shape's Fill, which is right there (Ellipse's Fill); to GradientStops[0] of a GreadientBrush, which there are 2 GradientStops in a RadialGradientBrush; and finally to the GradientStop's Color property, which is also there.
Does anyone has a suggestion?
Thanks in advance.

Answer 1

Someone helped me with a solution (I don't know if you would call it a direct solution or a work-around):
If you give a name to the GradientStop you can reference its Color property directly:
<Ellipse.Fill>
<RadialGradientBrush>
<GradientStop x:Name="Offset0" Color="Red"/>
<GradientStop x:Name="Offset1" Offset="1" Color="#00FF0000"/>
</RadialGradientBrush>
</Ellipse.Fill>
[...]
<VisualState x:Name="Checked">
<Storyboard>
<ColorAnimationUsingKeyFrames Storyboard.TargetProperty="Color" Storyboard.TargetName="Offset0">
<EasingColorKeyFrame KeyTime="0:0:0.3" Value="Red"/>
</ColorAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
<VisualState x:Name="Unchecked">
<Storyboard>
<ColorAnimationUsingKeyFrames Storyboard.TargetProperty="Color" Storyboard.TargetName="Offset0">
<EasingColorKeyFrame KeyTime="0:0:0.2" Value="#00FF0000"/>
</ColorAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
I guess that this approach shouldn't be necessary, but it certainly looks elegant.