Why the trigger doesn't work after GridSplitter is dragged - wpf

Question

Due to project privacy protection, I can't paste the product code here. So I made a simple example to show the problem.
I have a window like this:
When I click the Right button, I want the Right Column hide and the Left Column Stretch to full window:
Here is my Xaml:
<Window x:Class="WpfApplication1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition MinWidth="0"/>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition x:Name="rightCol" MinWidth="0"/>
</Grid.ColumnDefinitions>
<StackPanel Grid.Column="0">
<Button Height="100" Content="Left" />
</StackPanel>
<GridSplitter Grid.Column="1" Width="10" VerticalAlignment="Stretch" HorizontalAlignment="Center"/>
<StackPanel x:Name="right" Grid.Column="2" >
<Button Height="100" Content="Right" Click="Button_Click" />
</StackPanel>
</Grid>
</Window>
And here is my code-behind:
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
public override void OnApplyTemplate()
{
base.OnApplyTemplate();
var b = new Binding("Visibility")
{
Source = this.right
};
var style = new Style(typeof(ColumnDefinition))
{
Setters =
{
new Setter(ColumnDefinition.WidthProperty, new GridLength(300)),
new Setter(ColumnDefinition.MinWidthProperty, 0.0),
}
};
style.Triggers.Add(new DataTrigger()
{
Binding = b,
Value = System.Windows.Visibility.Collapsed,
Setters =
{
new Setter(ColumnDefinition.WidthProperty, new GridLength(0)),
new Setter(ColumnDefinition.MaxWidthProperty, double.PositiveInfinity),
new Setter(ColumnDefinition.MinWidthProperty, 0.0),
}
});
this.rightCol.Style = style;
}
private void Button_Click(object sender, RoutedEventArgs e)
{
this.right.Visibility = System.Windows.Visibility.Collapsed;
}
}
When I run it and Click the Right button, it works fine. But if I drag the GridSplitter before I Click the Right button, the trigger doesn't work:
Why this happened?
Note:
If I use below code, it can work.
private void Button_Click(object sender, RoutedEventArgs e)
{
this.right.Visibility = System.Windows.Visibility.Collapsed;
this.rightCol.Width = new GridLength(0);
}
But is there any way to use trigger?

Answer 1

I got my answer from this link:
GridSplitter overrides ColumnDefinition's style trigger?
So below code works fine:
public override void OnApplyTemplate()
{
base.OnApplyTemplate();
var b = new Binding("Visibility")
{
Source = this.rightPane,
Mode = BindingMode.OneWay
};
var style = new Style(typeof(ColumnDefinition))
{
Setters =
{
new Setter(ColumnDefinition.WidthProperty, new GridLength(300)),
new Setter(ColumnDefinition.MinWidthProperty, 0.0),
}
};
/*
style.Triggers.Add(new DataTrigger()
{
Binding = b,
Value = System.Windows.Visibility.Collapsed,
Setters =
{
new Setter(ColumnDefinition.WidthProperty, new GridLength(0)),
new Setter(ColumnDefinition.MaxWidthProperty, double.PositiveInfinity),
new Setter(ColumnDefinition.MinWidthProperty, 0.0),
}
});*/
Storyboard sb = new Storyboard();
ObjectAnimationUsingKeyFrames oaf = new ObjectAnimationUsingKeyFrames();
DiscreteObjectKeyFrame disobj = new DiscreteObjectKeyFrame();
disobj.KeyTime = TimeSpan.FromMilliseconds(0);
disobj.Value = GridLength.Auto;
oaf.KeyFrames.Add(disobj);
sb.Children.Add(oaf);
Storyboard.SetTargetProperty(oaf, new PropertyPath(ColumnDefinition.WidthProperty));
var actionBegin = new BeginStoryboard();
actionBegin.Storyboard = sb;
actionBegin.Name="BeginStoryboard1";
var actionEnd = new RemoveStoryboard();
actionEnd.BeginStoryboardName = "BeginStoryboard1";
var trigger = new DataTrigger()
{
Binding = b,
Value = System.Windows.Visibility.Collapsed
};
trigger.EnterActions.Add(actionBegin);
trigger.ExitActions.Add(actionEnd);
style.Triggers.Add(trigger);
style.RegisterName(actionBegin.Name, actionBegin);
this.rightCol.Style = style;
}