如果選擇了組合框項，C# WPF 更改網格可見性

Question

I'm trying to display a Grid and its contents when an item (anyone) in combobox is selected. 如果未選擇任何內容，網格將保持隱藏狀態。

XAML

    <ComboBox x:Name="cb" HorizontalAlignment="Left" VerticalAlignment="Top" Width="140" Height="25"/>
    <Grid x:Name="gr" Visibility="Hidden">
            <Border BorderThickness="1" HorizontalAlignment="Left" Height="600"  VerticalAlignment="Top" Width="346">
                <Border  BorderThickness="1" RenderTransformOrigin="0.5,0.5">
            </Border>
    </Grid>

我試過這個：

XAML文件

public void ChangeVisibility(ComboBox cb, Grid gr)
    {
        if (cb.SelectedItem != null)
        {
            gr.Visibility = Visibility.Visible;
        }
        else
        {
            gr.Visibility = Visibility.Hidden;
        }

但它不會改變任何東西。 我已經嘗試了多種方式，即使使用string.IsNullOrEmpty 。 combobox來源是List<string> 。

編輯

方法在這里被調用

public MainWindow()
        {
            InitializeComponent();
            WindowStartupLocation = WindowStartupLocation.CenterScreen;
            ChangeVisibility(cb, gr);
        }

Answer 1

 <ComboBox x:Name="cb" HorizontalAlignment="Left" VerticalAlignment="Top" Width="140" Height="25"/>
    <Grid x:Name="gr">
        <Grid.Style>
            <Style TargetType="Grid">
                <Setter Property="Visibility" Value="Visible"/>
                <Style.Triggers>
                    <DataTrigger Binding="{Binding ElementName=cb, Path=SelectedItem}" Value="{x:Null}">
                        <Setter Property="Visibility" Value="Collapsed"/>
                    </DataTrigger>
                </Style.Triggers>
            </Style>
        </Grid.Style>
        <Border BorderThickness="1" HorizontalAlignment="Left" Height="600"  VerticalAlignment="Top" Width="346">
            <Border  BorderThickness="1" RenderTransformOrigin="0.5,0.5">
            </Border>
    </Grid>

Answer 2

試試

主窗口.xaml.cs

private void ComboBox_Selected(object sender, RoutedEventArgs e)
{
    var item = Combo.SelectedItem as ComboBoxItem;
    if (item.Content.ToString() == "Visible")
    {
        RedGrid.Visibility = System.Windows.Visibility.Visible;
    }
    else

    {
        RedGrid.Visibility = System.Windows.Visibility.Hidden;
    }
}

主窗口.xaml：

<Grid>
    <Grid.RowDefinitions>
        <RowDefinition Height="30"/>
        <RowDefinition />
    </Grid.RowDefinitions>
    <ComboBox Name="Combo" SelectionChanged="ComboBox_Selected">
        <ComboBoxItem Content="Visible" />
        <ComboBoxItem Content="Hidden" />
    </ComboBox>
    <Grid Name="RedGrid" Grid.Row="1" Background="Red">

    </Grid>
</Grid>

或者更類似於您的問題：

主窗口.xaml.cs：

private void ComboBox_Selected(object sender, RoutedEventArgs e)
{
    var item = Combo.SelectedItem as ComboBoxItem;
    if (item != null)
    {
        RedGrid.Visibility = System.Windows.Visibility.Visible;
    }
}

主窗口.xaml：

<ComboBox Name="Combo" SelectionChanged="ComboBox_Selected" >
    <ComboBoxItem Content="Element 1" />
    <ComboBoxItem Content="Element 2" />
</ComboBox>
<Grid Name="RedGrid" Grid.Row="1" Background="Red" Visibility="Hidden">

</Grid>

但我不確定，你的方法是否正確。 您無法輕松取消選擇 ComboBox 中的項目，因此基本上，如果您選擇任何內容，網格將始終可見。 我寧願選擇具有多個 ComboBoxItem 的解決方案，其中一個將是“無”、“隱藏”或諸如此類。

您總是可以考慮在 WPF 框架中非常流行的 MVVM 模式