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根据第二个组合框的选择隐藏组合框项,反之亦然

visibility combobox wpf c#

1

nuuse · 技术社区 · 8 年前

我有两个组合框,每个都是绑定的(!)同样的 ObservableCollection<string> . 我想防止选择相同的项目。

这是我的C代码(firstload bool只是为了防止在第一次加载函数时执行):

private void comboBoxFilter1_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
    if (!firstload)
    {
        for (int i = 0; i <= comboBoxFilter2.Items.Count - 1; i++)
        {
            if ((((ComboBoxItem)(comboBoxFilter2.Items[i])).Content as string) == (((ComboBoxItem)comboBoxFilter1.SelectedItem).Content as string))
            // This is where I get the InvalidCaseException ^
            {
                (comboBoxFilter2.Items[i] as ComboBoxItem).Visibility = System.Windows.Visibility.Collapsed;
                //and on this line the nullreferenceException, in particular, although the Item[i] does have Value!
            }
            else
            {
                (comboBoxFilter2.Items[i] as ComboBoxItem).Visibility = System.Windows.Visibility.Visible;
                //and on this line the nullreferenceException, in particular, although the Item[i] does have Value!
            }
        }
    }
}

private void comboBoxFilter2_SelectionChanged(object sender, SelectionChangedEventArgs e)
{            
    if (!firstload)
    {
        for (int i = 0; i <= comboBoxFilter1.Items.Count - 1; i++)
        {
            if ((((ComboBoxItem)(comboBoxFilter1.Items[i])).Content as string) == (((ComboBoxItem)comboBoxFilter2.SelectedItem).Content as string))
            {
                (comboBoxFilter1.Items[i] as ComboBoxItem).Visibility = System.Windows.Visibility.Collapsed;
            }
            else
            {
                MessageBox.Show((comboBoxFilter2.Items[i] as ComboBoxItem).Visibility.ToString());
                (comboBoxFilter1.Items[i] as ComboBoxItem).Visibility = System.Windows.Visibility.Visible;
            }
        }
    }

    firstload = false;
}

这是我的Xaml:

<ComboBox x:Name="comboBoxFilter1" 
          Grid.Column="0" 
          Grid.Row="2"     
          HorizontalAlignment="Stretch" 
          VerticalAlignment="Bottom"     
          SelectionChanged="comboBoxFilter1_SelectionChanged" 
          SelectedIndex="0"     
          Visibility="Visible"/>    

<ComboBox x:Name="comboBoxFilter2" 
          Grid.Column="1" Grid.Row="2"     
          HorizontalAlignment="Stretch" 
          VerticalAlignment="Bottom"     
          SelectionChanged="comboBoxFilter2_SelectionChanged" 
          SelectedIndex="1"    
          Visibility="Visible"/>

注意,我在代码中执行Itemsource,而不是在Xaml中。

NullReferenceExecption 或者 InvalidCastException (参见代码中的注释)。同样的错误也发生在 comboBoxFilter2_SelectionChange

1 回复 | 直到 6 年前

1

3

Sinatr 8 年前

<StackPanel>
    <ComboBox ItemsSource="{Binding List1}" SelectedItem="{Binding Selected1}" />
    <ComboBox ItemsSource="{Binding List2}" SelectedItem="{Binding Selected2}" />
</StackPanel>

public class ViewModel : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;
    public void OnPropertyChanged([CallerMemberName] string property = "") => 
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(property));

    readonly List<string> _list = new List<string> { "a", "b", "c", "d", "e" };
    public IEnumerable<string> List1 => _list.Where(o => o != Selected2);
    public IEnumerable<string> List2 => _list.Where(o => o != Selected1);

    string _selected1;
    public string Selected1
    {
        get { return _selected1; }
        set
        {
            _selected1 = value;
            OnPropertyChanged();
            OnPropertyChanged(nameof(List2));
        }
    }

    string _selected2;
    public string Selected2
    {
        get { return _selected2; }
        set
        {
            _selected2 = value;
            OnPropertyChanged();
            OnPropertyChanged(nameof(List1));
        }
    }
}

注意:当视图更改所选项目时,viewmodel只会触发 NotifyPropertyChanged 评估绑定中使用的属性及其值的事件。

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
        DataContext = new ViewModel() { Selected1 = "a", Selected2 = "d" };
    }
}