wpf databind IsVisible to TabControl.SelectedItem！= null

Question

我有一個StackPanel，我只想讓SomeTabControl.SelectedItem != null可見。我如何在WPF綁定中做到這一點？

Answer 1

您可以使用樣式和觸發做到無需轉換器：

<StackPanel> 
    <StackPanel.Style> 
     <Style TargetType="{x:Type StackPanel}"> 
      <Setter Property="Visibility" Value="Visible" /> 
      <Style.Triggers> 
       <DataTrigger 
        Binding="{Binding SelectedItem,ElementName=tabControl1}" 
        Value="{x:Null}"> 
        <Setter Property="Visibility" Value="Hidden" /> 
       </DataTrigger> 
      <Style.Triggers> 
     </Style> 
    </StackPanel.Style> 
</StackPanel> 

這個例子默認顯示的StackPanel，但然後隱藏它當tabControl1的的SelectedItem爲null。

Answer 2

創建一個轉換器，將可空值轉換爲System.Windows.Visibility值並將其用於綁定。

例如：

<StackPanel x:Name="myPanel" Visibility="{Binding Path=SelectedItem, Mode=OneWay, ElementName=SomeTabControl, Converter={StaticResource visibilityConverter}}" /> 

代碼轉換器類：

public class VisibilityConverter : IValueConverter 
{ 
    #region [ IValueConverter ] 

    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) 
    { 
     if(value == null) 
      return System.Windows.Visibility.Collapsed; 

     return System.Windows.Visibility.Visible; 
    } 

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) 
    { 
     throw new NotSupportedException(); 
    } 

    #endregion 
} 

附：這假設在您的控件的XAML中有一個名爲visibilityConverter的靜態資源。