Question

我创建了两个组合框，一个用于类别，一个用于项目。我想要的是当类别改变时，项目也将被改变。这是我的XAML：

<Window x:Class="ComboBoxTest.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWindow" Height="100" Width="202">
    <Grid>
        <ComboBox Height="23" HorizontalAlignment="Left" Name="comboBox1" VerticalAlignment="Top" Width="171"
                  ItemsSource="{Binding CategoryList}"
                  DisplayMemberPath="Name"
                  SelectedItem="{Binding SelectedCategory}"/>
        <ComboBox Height="23" HorizontalAlignment="Left" Margin="0,29,0,0" Name="comboBox2" VerticalAlignment="Top" Width="171"
                  ItemsSource="{Binding ItemList}"
                  DisplayMemberPath="Name"
                  SelectedItem="{Binding SelectedItem}"/>
    </Grid>
</Window>

这是代码隐藏：

namespace ComboBoxTest
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window, INotifyPropertyChanged
{
    private List<Categories> _CategoryList = new List<Categories>();
    private List<Items> _ItemList = new List<Items>();

    private Categories _SelectedCategory;
    private Items _SelectedItem;

    public MainWindow()
    {
        InitializeComponent();
        DataContext = this;
        _CategoryList.Add(new Categories(1, "Car"));
        _CategoryList.Add(new Categories(2, "Truck"));
        _CategoryList.Add(new Categories(3, "Motorcycle"));
        SelectedCategory = _CategoryList[0];
    }

    public List<Categories> CategoryList
    {
        get { return _CategoryList; }
    }
    public List<Items> ItemList
    {
        get { return _ItemList; }
    }

    public Categories SelectedCategory
    {
        get { return _SelectedCategory; }
        set 
        { 
            _SelectedCategory = value;
            OnPropertyChanged("SelectedCategory");
            UpdateItems();
            OnPropertyChanged("ItemList");
        }
    }
    public Items SelectedItem
    {
        get { return _SelectedItem; }
        set
        {
            _SelectedItem = value;
            OnPropertyChanged("SelectedItem");
        }
    }

    private void UpdateItems()
    {
        _ItemList.Clear();

        switch (_SelectedCategory.ID)
        {
            case 1:
                _ItemList.Add(new Items("BMW"));
                break;
            case 2:
                _ItemList.Add(new Items("Ford"));
                break;
            case 3:
                _ItemList.Add(new Items("Harley"));
                break;
            default:
                Console.WriteLine("Something is wrong");
                break;
        }
        if (_ItemList.Count != 0)
        {
            SelectedItem = _ItemList[0];
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;
    protected virtual void OnPropertyChanged(string propertyName)
    {
        PropertyChangedEventHandler handler = this.PropertyChanged;
        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

public class Categories
{
    private int _ID;
    private string _Name;

    public Categories(int id, string name)
    {
        _ID = id;
        _Name = name;
    }

    public int ID
    {
        get { return _ID; }
        set { _ID = value; }
    }

    public string Name
    {
        get { return _Name; }
        set { _Name = value; }
    }
}

public class Items
{
    public string _Name;

    public Items(string name)
    {
        _Name = name;
    }

    public string Name
    {
        get { return _Name; }
        set { _Name = value; }
    } 
}
}

乍一看，看起来很好。当我从汽车改为卡车时，物品清单从宝马变为福特。问题是如果我花费项目列表然后更改类别，新类别的项目列表将具有上一类别中的项目。我无法解决这个问题。任何帮助表示赞赏。

Answer 1

我的建议是使用ObservableCollection而不是简单List<>。

    private ObservableCollection<Categories> _CategoryList = new ObservableCollection<Categories>();
    private ObservableCollection<Items> _ItemList = new ObservableCollection<Items>();

    private Categories _SelectedCategory;
    private Items _SelectedItem;

    public MainWindow()
    {
        InitializeComponent();
        DataContext = this;
        _CategoryList.Add(new Categories(1, "Car"));
        _CategoryList.Add(new Categories(2, "Truck"));
        _CategoryList.Add(new Categories(3, "Motorcycle"));
        SelectedCategory = _CategoryList[0];
    }

    public ObservableCollection<Categories> CategoryList
    {
        get { return _CategoryList; }
    }
    public ObservableCollection<Items> ItemList
    {
        get { return _ItemList; }
    }

或者，在完成PropertyChanged更新后，您必须从ItemList方法提升UpdateItems() ItemList。

级联组合框与一个额外项目

1 个答案: