Expander getting stuck after IsExpanded set to true by storyboard

Question

So I have an expander that I want to have the normal functionality (open and close with its own button) but I also want a different button to expand it when pressed (this button is in the header of the expander). I'm using a storyboard in an event trigger for the Button.Click which works, but after it is expanded this way the normal button doesn't work, it just stays expanded. My xaml is below, I would really prefer to keep this all in the xaml, I could come up with a way to do it in the codebehind/viewmodel myself.

<Expander x:Name="IndexExpander" IsExpanded="True" Grid.Row="4" Grid.ColumnSpan="5" Margin="10" MaxHeight="150">
                <Expander.Triggers>
                    <EventTrigger SourceName="btnAddIndex" RoutedEvent="Button.Click">
                        <BeginStoryboard>
                            <Storyboard>
                                <BooleanAnimationUsingKeyFrames Storyboard.TargetName="IndexExpander" Storyboard.TargetProperty="IsExpanded" BeginTime="0:0:0.25" Duration="0:0:0.20" >
                                    <DiscreteBooleanKeyFrame KeyTime="0" Value="True" />
                                </BooleanAnimationUsingKeyFrames>
                            </Storyboard>
                        </BeginStoryboard>
                    </EventTrigger>
                </Expander.Triggers>
                <Expander.Header>
                    <StackPanel DockPanel.Dock="Left" Orientation="Horizontal">
                        <TextBlock Text="Indexes" FontWeight="Bold"/>

                        <!-- Add/Delete Buttons-->
                        <Grid Margin="10,0,0,0">
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition Width="50*"/>
                                <ColumnDefinition Width="50*"/>
                            </Grid.ColumnDefinitions>
                            <Button Grid.Column="0" x:Name="btnAddIndex" Command="{Binding AddIndexCommand}" Template="{StaticResource AddButtonTemplate}" IsEnabled="{Binding IsEditable}" Margin="0,0,5,0" />
                        </Grid>
                    </StackPanel>
                </Expander.Header>

Answer 1

Alright, so for anyone following in my footsteps here's what I did. I got the idea from here, and adapted it until it worked correctly.

<Expander.Triggers>
    <EventTrigger SourceName="btnAddCol" RoutedEvent="Button.Click">
        <BeginStoryboard x:Name="ColumnExpanderStory">
            <Storyboard>
                <BooleanAnimationUsingKeyFrames Storyboard.TargetName="ColumnExpander" Storyboard.TargetProperty="IsExpanded">
                    <DiscreteBooleanKeyFrame KeyTime="0" Value="True" />
                </BooleanAnimationUsingKeyFrames>
             </Storyboard>
         </BeginStoryboard>
     </EventTrigger>
     <EventTrigger RoutedEvent="ToggleButton.PreviewMouseUp">
         <RemoveStoryboard BeginStoryboardName="ColumnExpanderStory" />
     </EventTrigger>
  </Expander.Triggers>
<Expander.Header>

The problem was that the storyboard overrides any other bindings to the IsExpanded property, so it has to be removed to restore them (read more here). The suggestion was to use the ToggleButton.Checked event to remove the storyboard, but that didn't work for me, only the "Preview" events seemed to have the right timing. I started with PreviewMouseDown, but it would remove the storyboard, then on mouse up toggle the expander, meaning the first click would just flip states back and forth quickly. Using PreviewMouseUp got around that issue.