How to bind the IsChecked of a checkbox to Expander IsExpanded within a datagrid

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WPF

checkbox

Binding

Okay, I'm getting highly frustrated right now, and keep in mind that I am brand new to WPF and binding so..

I have a

Datagrid (that is within a tabcontrol). Within the Datagrid is an expander. I have a checkbox at the top of the Window called chkExpandAll. I want to bind the IsExpanded of the expander to the IsChecked of the checkbox. In other words I wish to expand all of the expanders in the datagrid when I select the checkbox.

In my Windows Resources section I have:

<local:BooleanToVisibilityConverter x:Key="boolConvertNormal" />

The checkbox is listed as:

<CheckBox Content="Expand All" Name="chkExpandAll" VerticalAlignment="Center" Margin="5,0,5,0" />

And then on my expander I have this:

<Expander Header="{Binding}" IsExpanded="{Binding IsChecked, ElementName=chkExpandAll, Converter={StaticResource ResourceKey=boolConvertNormal}, Mode=TwoWay}"  >

When I run the app and then click the checkbox nothing happens.

Oh, and here is the code for the resource:

public sealed class BooleanToVisibilityConverter : IValueConverter
   {
       public bool IsReversed { get; set; }
       public bool UseHidden { get; set; }
       public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
       {
           var val = System.Convert.ToBoolean(value, CultureInfo.InvariantCulture);
           if (this.IsReversed)
           {
               val = !val;
           }
           if (val)
           {
               return Visibility.Visible;
           }
           return this.UseHidden ? Visibility.Hidden : Visibility.Collapsed;
       }
       public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
       {
           throw new NotImplementedException();
       }
   }