Question

I have a ListView with some GridViewColumns and I’d like to be able to show or hide them through checkable items in a ContextMenu.

MainView.xaml:

<ListView>
  <ListView.ContextMenu>
    <ContextMenu>
      <MenuItem x:Name="cma" Header="a" IsCheckable="True" IsChecked="True"/>
      <MenuItem x:Name="cmb" Header="b" IsCheckable="True"/>
      <MenuItem x:Name="cmc" Header="c" IsCheckable="True" IsChecked="True"/>
      <MenuItem x:Name="cmd" Header="d" IsCheckable="True"/>
    </ContextMenu>
  </ListView.ContextMenu>
  <ListView.View>
    <GridView>
      <c:GridViewColumnExt c:GridViewColumnExt.IsVisible="{Binding ElementName=cma, Path=IsChecked}">
        <GridViewColumnHeader Content="a"/>
      </c:GridViewColumnExt>
      <c:GridViewColumnExt c:GridViewColumnExt.IsVisible="{Binding ElementName=cmb, Path=IsChecked}">
        <GridViewColumnHeader Content="b"/>
      </c:GridViewColumnExt>
      <c:GridViewColumnExt c:GridViewColumnExt.IsVisible="{Binding ElementName=cmc, Path=IsChecked}">
        <GridViewColumnHeader Content="c"/>
      </c:GridViewColumnExt>
      <c:GridViewColumnExt c:GridViewColumnExt.IsVisible="{Binding ElementName=cmd, Path=IsChecked}">
        <GridViewColumnHeader Content="d"/>
      </c:GridViewColumnExt>
    </GridView>
  </ListView.View>
</ListView>

GridViewColumnExt.cs:

public class GridViewColumnExt : GridViewColumn
{
  private double _visibleWidth = double.NaN;

  public bool IsVisible
  {
    get { return (bool)GetValue(IsVisibleProperty); }
    set { SetValue(IsVisibleProperty, value); }
  }

  public static readonly DependencyProperty IsVisibleProperty = DependencyProperty.Register("IsVisible", typeof(bool), typeof(GridViewColumnExt), new FrameworkPropertyMetadata(true, OnIsVisibleChanged));

  private static void OnIsVisibleChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
  {
    var newValue = bool.Parse(e.NewValue.ToString());
    var column = (GridViewColumnExt)d;
    var header = (GridViewColumnHeader)column.Header;
    header.IsEnabled = newValue;
    if (newValue)
    {
      column.Width = column._visibleWidth;
      header.IsEnabled = true;
      header.Visibility = Visibility.Visible;
    }
    else
    {
      column._visibleWidth = column.Width;
      column.Width = 0;
      header.IsEnabled = false;
      header.Visibility = Visibility.Collapsed;
    }
  }
}

MainViewModel.cs (Never mind, the solution doesn’t need this)

The problem:

• When the window is first shown, columns a and c are visible
• When the ContextMenu is first shown, columns a and c become hidden and only column b is shown. Also, only column b is checked in the ContextMenu

Does anyone know what causes this?

Solution:

Removed binding to ViewModel properties and and just set the MenuItem.IsChecked to a default value.
By the way, if anyone has an even better way of handling this kind of stuff, please let me know 🙂

Answer 1

FallbackValue is for when a binding is unable to return a value. Column b is checked and visible because you’re setting it to true in the constructor. Update your constructor appropriately.

public class MainViewModel
{
  public MainViewModel()
  {
    ColumnChecked_a = true;
    ColumnChecked_b = true;
    ColumnChecked_c = true;
  }
}

Also, I’m thinking the columns’ visibility changes because the contextmenu maybe isn’t “created” until the right-click. Try a normal menu and see if that works, yeah.