wpf use VisualStateManager to change Visibility - wpf

Question

I'm working on transitioning some code from silverlight to WPF, and my VisualStates are not working correctly.
I am using visualstatemanager to control the visibility of some text fields. I am not using any transitions to animate the change, I just want the fields to be collapsed in one state, then visible in another.
Xaml from silverlight:
<VisualStateManager.VisualStateGroups>
<VisualStateGroup x:Name="LostPasswordStates">
<VisualState x:Name="LostPassword_Start">
<Storyboard>
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="lbl_UserName" Storyboard.TargetProperty="(UIElement.Visibility)">
<DiscreteObjectKeyFrame KeyTime="00:00:00" Value="Visible" />
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="txt_UserName" Storyboard.TargetProperty="(UIElement.Visibility)">
<DiscreteObjectKeyFrame KeyTime="00:00:00" Value="Visible" />
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="txt_UserName" Storyboard.TargetProperty="(TextBox.IsReadOnly)">
<DiscreteObjectKeyFrame KeyTime="00:00:00" Value="False" />
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
<VisualState x:Name="LostPassword_Success">
<Storyboard>
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="lbl_UserName" Storyboard.TargetProperty="(UIElement.Visibility)">
<DiscreteObjectKeyFrame KeyTime="00:00:00" Value="Collapsed" />
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="txt_UserName" Storyboard.TargetProperty="(UIElement.Visibility)">
<DiscreteObjectKeyFrame KeyTime="00:00:00" Value="Collapsed" />
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="btn_Reset" Storyboard.TargetProperty="(UIElement.Visibility)">
<DiscreteObjectKeyFrame KeyTime="00:00:00" Value="Collapsed" />
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
I get the following exception :
An unhandled exception of type 'System.Windows.Media.Animation.AnimationException' occurred in PresentationCore.dll
Additional information: Cannot animate the 'Visibility' property on a 'System.Windows.Controls.TextBox' using a 'System.Windows.Media.Animation.ObjectAnimationUsingKeyFrames'. For details see the inner exception.
So my question to you is:
If I can't use a System.Windows.Media.Animation.ObjectAnimationUsingKeyFrames for this, what should I be using?

Answer 1

This works for me, using .NET 4.5:
<VisualStateManager.VisualStateGroups>
<VisualStateGroup x:Name="LostPasswordStates">
<VisualState x:Name="LostPassword_Start">
<Storyboard>
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="lbl_UserName" Storyboard.TargetProperty="(UIElement.Visibility)">
<DiscreteObjectKeyFrame KeyTime="00:00:00" Value="{x:Static Visibility.Visible}" />
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="txt_UserName" Storyboard.TargetProperty="(UIElement.Visibility)">
<DiscreteObjectKeyFrame KeyTime="00:00:00" Value="{x:Static Visibility.Visible}" />
</ObjectAnimationUsingKeyFrames>
<BooleanAnimationUsingKeyFrames Storyboard.TargetName="txt_UserName" Storyboard.TargetProperty="(TextBox.IsReadOnly)">
<DiscreteBooleanKeyFrame KeyTime="00:00:00" Value="False" />
</BooleanAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
<VisualState x:Name="LostPassword_Success">
<Storyboard>
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="lbl_UserName" Storyboard.TargetProperty="(UIElement.Visibility)">
<DiscreteObjectKeyFrame KeyTime="00:00:00" Value="{x:Static Visibility.Collapsed}" />
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="txt_UserName" Storyboard.TargetProperty="(UIElement.Visibility)">
<DiscreteObjectKeyFrame KeyTime="00:00:00" Value="{x:Static Visibility.Collapsed}" />
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="btn_Reset" Storyboard.TargetProperty="(UIElement.Visibility)">
<DiscreteObjectKeyFrame KeyTime="00:00:00" Value="{x:Static Visibility.Collapsed}" />
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
There are two changes to your current code:
Instead of "Collapsed" and "Visible", the Value is set to "{x:Static Visibility.Collapsed}" and "{x:Static Visibility.Visible}";
The IsReadOnly property uses a BooleanAnimationUsingKeyFrames instead of an ObjectAnimationUsingKeyFrames;

Answer 2

You can only animate properties of numeric types (double). Visibility can not be animated because it is enum an there is no way to animate this meaningfull.
If you want to fadeout something you can use the opacity property.