如何在C# WinForm中根据ComboBoxA选择切换ComboBoxB数据源

我通过代码在WPF窗体中动态添加了两个ComboBox，需求是根据ComboBoxA的选择切换ComboBoxB的数据源：默认ComboBoxB使用itemsource_1，当ComboBoxA选中"4"时，ComboBoxB的数据源切换为itemsource_4。已为ComboBoxA添加SelectionChanged事件处理程序，但无法在事件中访问ComboBoxB，求解决办法。

相关代码片段 #

动态添加ComboBox的代码

string[] comboboxAitemsource = { "1", "2", "3", "4"};
string[] itemsource_1 = { "11", "12", "13", "14"};
string[] itemsource_2 = { "21", "22", "23", "24"};
string[] itemsource_3 = { "31", "32", "33", "34"};
string[] itemsource_4 = { "41", "42", "43", "44"};

int left_margin = 10, top_margin = margin, margin_inc = 40, sec_left_margin = 300;
System.Windows.Controls.Label ComboboxAlabel = new System.Windows.Controls.Label();
ComboboxAlabel.HorizontalAlignment = System.Windows.HorizontalAlignment.Left; ;
ComboboxAlabel.VerticalAlignment = VerticalAlignment.Top;
ComboboxAlabel.Name = "typeComboboxAlabel";
ComboboxAlabel.Content = "COMBOBOX A";
ComboboxAlabel.Height = 40;
ComboboxAlabel.Margin = new Thickness((double)left_margin, (double)top_margin, (double)10, (double)0);
grid.Children.Add(ComboboxAlabel);


System.Windows.Controls.ComboBox comboboxA = new System.Windows.Controls.ComboBox();
comboboxA.HorizontalAlignment = System.Windows.HorizontalAlignment.Left; ;
comboboxA.VerticalAlignment = VerticalAlignment.Top;
comboboxA.Name = "typeCombobox";
comboboxA.Height = 20;
comboboxA.Width = 250;
comboboxA.Margin = new Thickness((double)sec_left_margin, (double)top_margin, (double)10, (double)0);
comboboxA.ItemsSource = comboboxAitemsource;
comboboxA.SelectedIndex = 0;
comboboxA.SelectionChanged += new System.Windows.Controls.SelectionChangedEventHandler(typeCombobox_SelectionChangedEventHandler);
top_margin = top_margin + margin_inc;
grid.Children.Add(comboboxA);

System.Windows.Controls.Label comboboxBlabel = new System.Windows.Controls.Label();
comboboxBlabel.HorizontalAlignment = System.Windows.HorizontalAlignment.Left;
comboboxBlabel.VerticalAlignment = VerticalAlignment.Top;
comboboxBlabel.Name = "typeLabelUpdate";
comboboxBlabel.Content = "COMBOBOX B";
comboboxBlabel.Height = 40;
comboboxBlabel.Margin = new Thickness((double)left_margin, (double)top_margin, (double)10, (double)0);
grid.Children.Add(comboboxBlabel);

System.Windows.Controls.ComboBox comboboxB = new System.Windows.Controls.ComboBox();
comboboxB.HorizontalAlignment = System.Windows.HorizontalAlignment.Left;
comboboxB.VerticalAlignment = VerticalAlignment.Top;
comboboxB.Name = "typeComboBoxUpdate";
comboboxB.Height = 20;
comboboxB.Width = 250;
comboboxB.Margin = new Thickness((double)sec_left_margin, (double)top_margin, (double)10, (double)0);
comboboxB.ItemsSource = itemsource_1;
comboboxB.SelectedIndex = 0;
top_margin = top_margin + margin_inc;
grid.Children.Add(comboboxB);

ComboBoxA的事件处理程序

private void typeCombobox_SelectionChangedEventHandler(object sender, EventArgs e)
{
    ComboBox comboBox = (ComboBox)sender;
    
}

解决办法 #

方法1：将ComboBoxB声明为类级成员变量 #

在窗体类中定义一个成员变量存储ComboBoxB，这样事件处理程序可以直接访问它。

1. 在窗体类的顶部添加成员变量：

private ComboBox _comboboxB;

2. 在动态创建ComboBoxB时，将实例赋值给该成员变量：

// 创建comboboxB的代码...
_comboboxB = comboboxB; // 赋值给类成员变量
grid.Children.Add(comboboxB);

3. 修改事件处理程序：

private void typeCombobox_SelectionChangedEventHandler(object sender, SelectionChangedEventArgs e)
{
    ComboBox comboBoxA = (ComboBox)sender;
    string selectedValue = comboBoxA.SelectedItem.ToString();

    // 根据选中值切换ComboBoxB的数据源
    switch(selectedValue)
    {
        case "1":
            _comboboxB.ItemsSource = itemsource_1;
            break;
        case "2":
            _comboboxB.ItemsSource = itemsource_2;
            break;
        case "3":
            _comboboxB.ItemsSource = itemsource_3;
            break;
        case "4":
            _comboboxB.ItemsSource = itemsource_4;
            break;
    }
    _comboboxB.SelectedIndex = 0; // 重置默认选中项
}

方法2：通过容器的Children集合查找ComboBoxB #

如果不想使用类成员变量，可以通过控件容器（这里是grid）的Children集合，根据控件名称查找ComboBoxB。

注意：需要引入System.Linq命名空间才能使用OfType和FirstOrDefault方法。

修改事件处理程序：

using System.Linq;

// ...

private void typeCombobox_SelectionChangedEventHandler(object sender, SelectionChangedEventArgs e)
{
    ComboBox comboBoxA = (ComboBox)sender;
    string selectedValue = comboBoxA.SelectedItem.ToString();

    // 从grid中查找名为"typeComboBoxUpdate"的ComboBox
    ComboBox comboBoxB = grid.Children.OfType<ComboBox>()
        .FirstOrDefault(cb => cb.Name == "typeComboBoxUpdate");

    if(comboBoxB != null)
    {
        switch(selectedValue)
        {
            case "1":
                comboBoxB.ItemsSource = itemsource_1;
                break;
            case "2":
                comboBoxB.ItemsSource = itemsource_2;
                break;
            case "3":
                comboBoxB.ItemsSource = itemsource_3;
                break;
            case "4":
                comboBoxB.ItemsSource = itemsource_4;
                break;
        }
        comboBoxB.SelectedIndex = 0;
    }
}

方法3：利用Tag属性传递ComboBoxB #

在绑定ComboBoxA的事件时，将ComboBoxB赋值给ComboBoxA的Tag属性，这样在事件处理程序中可以直接从sender的Tag中获取ComboBoxB。

1. 修改ComboBoxA的创建代码，添加Tag赋值：

comboboxA.Tag = comboboxB; // 将comboboxB绑定到comboboxA的Tag属性
comboboxA.SelectionChanged += typeCombobox_SelectionChangedEventHandler;

2. 修改事件处理程序：

private void typeCombobox_SelectionChangedEventHandler(object sender, SelectionChangedEventArgs e)
{
    ComboBox comboBoxA = (ComboBox)sender;
    // 从Tag中获取ComboBoxB实例
    ComboBox comboBoxB = comboBoxA.Tag as ComboBox;

    if(comboBoxB != null)
    {
        string selectedValue = comboBoxA.SelectedItem.ToString();
        switch(selectedValue)
        {
            case "1":
                comboBoxB.ItemsSource = itemsource_1;
                break;
            case "2":
                comboBoxB.ItemsSource = itemsource_2;
                break;
            case "3":
                comboBoxB.ItemsSource = itemsource_3;
                break;
            case "4":
                comboBoxB.ItemsSource = itemsource_4;
                break;
        }
        comboBoxB.SelectedIndex = 0;
    }
}

内容的提问来源于stack exchange，提问作者DeLorean