这可以通过一些绑定和可选的值转换器来完成。此示例假设您绑定到具有 Items 属性的模型,并且该属性的类型为 ObservableCollection,以便在添加/删除项目时集合的 Count 属性将触发属性更改。
<Grid>
<Grid.Resources>
<local:CountToVisbilityConverter x:Key="CountToVis"/>
</Grid.Resources>
....
<Grid Width="25" Height="25" Visibility="{Binding Items.Count, Converter=CountToVis}">
<Ellipse Fill="Red" Width="25" Height="25"/>
<ViewBox Width="25" Height="25">
<TextBlock Text="{Binding Itmes.Count}" Foreground="White"/>
</Viewbox>
</Grid>
</Grid>
和值转换器:
public class CountToVisibilityConverter : IValueConverter
{
#region IValueConverter Members
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if(value == null) return Visibility.Collapsed;
int count = System.Convert.ToInt32(value);
return count == 0 ? Visibility.Collapsed : Visibility.Visible;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
#endregion
}
我看到可选“转换器的原因是因为您还可以像这样使用交互数据触发器
<Grid x:Name="UnreadNotification" Width="25" Height="25">
<Ellipse Fill="Red" Width="25" Height="25"/>
<ViewBox Width="25" Height="25">
<TextBlock Text="{Binding Itmes.Count}" Foreground="White"/>
</Viewbox>
</Grid>
<i:Interaction.Triggers>
<ei:DataTrigger Binding="{Binding Items.Count, Comparison="Equal"
Value="0">
<ei:ChangePropertyAction PropertyName="IsEnabled"
Value="True"
TargetName="UnreadNotification" />
</ei:DataTrigger>
</i:Interaction.Triggers>