BooleanToVisibilityConverter，在真或空时转换为可见的，当为false时转换为折叠

Question

我在ThreeState ToggleButton和普通按钮之间做了一些绑定。

这就是我想要达到的目标：

button#1，如果button#2 IsChecked=True或Null可见的话

如果button#1 button#2 IsChecked=False崩溃

内置的BooleanToVisibilityConverter只在真时显示按钮。

如果你能帮忙改装，我将非常感激。谢谢

Answer 1

这太简单了。以下IValueConverter在value为true或null时返回true

public sealed class BooleanToVisibilityConverter : IValueConverter
{
  public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
  {
    return value is bool bValue && bValue 
      || value == null 
        ? Visibility.Visible 
        : Visibility.Collapsed;
  }

  public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
  {
    return value is Visibility visibility 
      && visibility == Visibility.Visible;
  }
}

Answer 2

没有BooleanToVisibilityConverter，只有XAML：

<Window.Resources>
    <Style TargetType="Button">
        <Setter Property="Visibility"
                Value="Visible" />
        <Style.Triggers>
            <DataTrigger Binding="{Binding ElementName=chk1, Path=IsChecked}"
                         Value="False">
                <Setter Property="Visibility"
                        Value="Collapsed" />
            </DataTrigger>
        </Style.Triggers>
    </Style>
</Window.Resources>
<Grid>
    <Button Content="Button"
            HorizontalAlignment="Left"
            Margin="34,68,0,0"
            VerticalAlignment="Top"
            Width="75" />
    <CheckBox x:Name="chk1"
              Content=" Toggle"
              HorizontalAlignment="Left"
              Margin="34,29,0,0"
              VerticalAlignment="Top"
              IsThreeState="True"
              IsChecked="True" />
</Grid>