Question

我有3个组合框

<Grid>
   <ComboBox Name="cbo1" SelectionChanged="OnComboBoxChanged" />
   <ComboBox Name="cbo2" SelectionChanged="OnComboBoxChanged"/>
   <ComboBox Name="cbo3" SelectionChanged="OnComboBoxChanged" />

组合框列表是{a，b，c，d} 所以如果＆＃34; b＆＃34;在第一个框中选择，然后下拉列表不应该有b，如果第二个设置为a，则需要更新{a，c，d}，然后最后一个需要{c，d}。如果他们回去改变我们需要相应更新列表。我添加了一个oncomboboxchanged事件，但当我将项目源设置为新列表时，它没有更新组合框。

private List<string> comboList = new List<string>();
string[] defaultParam = { "A", "B", "C", "D" };

public MainWindow()
{   
       InitializeComponent();
       foreach(string s in defaultParam)
       {
           LoadCombo(s);
       } 

}
public void LoadCombo(string name)
{
   comboList.Add(name); 
   cbo1.ItemsSource = comboList;
   cbo2.ItemsSource = comboList;
   cbo3.ItemsSource = comboList;
}
private void OnComboBoxChanged(object sender,SelectionChangedEventArgs e)
{
   var combo = sender as ComboBox;
   string oldval = combo.Text;
   string id = combo.Name;
   string itemSel = (sender as ComboBox).SelectedItem.ToString();
   comboList.Remove(itemSel);
   //add old value only if it is not empty
   if (!string.IsNullOrEmpty(oldval))
   {
      comboList.Add(oldval);
   }
   combo.ItemsSource = comboList;
   ComboBox[] comboNameLst = {cbo1,cbo2,cbo3 }; 
   foreach (ComboBox cbo in comboNameLst)
   {
       if (id != cbo.Name)
       {
          if (cbo.SelectedItem == null)
          {
              cbo.ItemsSource = comboList;
          }
          else if (cbo.SelectedItem != null)
          {
             string tempitemsel = cbo.SelectedItem.ToString();
             comboList.Add(tempitemsel);
             cbo.ItemsSource = comboList;
             comboList.Remove(tempitemsel);
          }
       }
   }
}

所以cbo.ItemSource没有做任何事情，我是否需要以不同的方式做任何事情，所以我看到了更新。

Answer 1

您需要在XAML中使用绑定，而不是在后面的代码中设置ItemsSource。数据绑定SelectedItem：

 <Grid>
     <ComboBox ItemsSource="{Binding DefaultList}" SelectedItem="{Binding SelectedItem_Cob1}"/>
     <ComboBox ItemsSource="{Binding FilteredListA}" SelectedItem="{Binding SelectedItem_Cob2}"/>
     <ComboBox ItemsSource="{Binding FilteredListB}" SelectedItem="{Binding SelectedItem_Cob3}"/>
 </Grid>

在您的代码中，您需要实现INotifyPropertyChanged;将您的相关ItemsSources和SlectedItems定义为属性;并将Windows的DataContext设置为您自己的代码（您应该使用MVVM模式但稍后可能会担心）：

using System.ComponentModel;
public partial class MainWindow: INotifyPropertyChanged
{ 
    string[] defaultParam = { "A", "B", "C", "D" };
    private string _selecteditem_cob1;
    private string _selecteditem_cob2;
    private string _selecteditem_cob3;

    public List<string> DefaultList
    {
        get { return defaultParam.ToList(); }
    }

    public string SelectedItem_Cob1
    {
        get { return _selecteditem_cob1; }
        set
        {
            if (_selecteditem_cob1 != value)
            {
                _selecteditem_cob1 = value;
                RaisePropertyChanged("SelectedItem_Cob1");
                RaisePropertyChanged("FilteredListA");
                RaisePropertyChanged("FilteredListB");
            }
        }
    }

    public string SelectedItem_Cob2
    {
        get { return _selecteditem_cob2; }
        set
        {
            if (_selecteditem_cob2 != value)
            {
                _selecteditem_cob2 = value;
                RaisePropertyChanged("SelectedItem_Cob2");
                RaisePropertyChanged("FilteredListB");
            }
        }
    }

    public string SelectedItem_Cob3
    {
        get { return _selecteditem_cob3; }
        set
        {
            if (_selecteditem_cob3 != value)
            {
                _selecteditem_cob3 = value;
                RaisePropertyChanged("SelectedItem_Cob3");
            }
        }
    }

    public List<string> FilteredListA
    {
        get { return defaultParam.ToList().Where(a=>a!=SelectedItem_Cob1).ToList(); }
    }
    public List<string> FilteredListB
    {
        get { return FilteredListA.Where(a => a != SelectedItem_Cob2).ToList(); }
    }
    public MainWindow()
    {

        InitializeComponent();  
        this.DataContext=this;          
    }

    //Implementation for INotifyPropertyChanged
    public event PropertyChangedEventHandler PropertyChanged;

    protected virtual void OnPropertyChanged(PropertyChangedEventArgs e)
    {
        var handler = this.PropertyChanged;
        if (handler != null)
        {
            handler(this, e);
        }
    }

    protected void RaisePropertyChanged(String propertyName)
    {
        OnPropertyChanged(new PropertyChangedEventArgs(propertyName));
    }
}

结果：

三个组合框将在初始阶段显示 A，B，C，D 。和   然后，如果用户选择cbo2，则cbo3将仅显示   动态过滤结果。

我意识到这不是你想要的100％（感谢@TheodosiusVonRichthofen），但我觉得你仍然可以使用它，并且能够轻松修改它以满足你的需要。

Answer 2

此外，包含组合框项的列表应该是ObservableCollection而不是List。通过使其成为ObservableCollection，当您在列表中添加/删除/更改项目时，将更新组合框项目。

WPF组合框没有绑定更改

2 个答案: