c# - WPF : Close combobox on item selection and display Message box

Question

目标 我在 WPF 中有组合框，每当用户从组合框中选择项目时，我想关闭组合框(将旧值显示为所选值)并显示带有确定/取消按钮的消息框。如果用户单击“确定”，则应设置新选定的值，否则应返回。

问题当我选择项目时，我可以显示消息框并打开组合框，但我不希望这样做。一旦用户选择某些内容，我想关闭组合框并显示消息框。

我该怎么做？

XMAL代码

 <ComboBox Name="Currency" Grid.Row="1" Grid.Column="5" ItemsSource="{Binding comboboxSource}"
                        SelectedValuePath="Value.bank_currency" IsReadOnly="False" IsTextSearchEnabled="True" TextSearch.TextPath="Value.bank_currency" 
                        SelectedItem="{Binding SelectedBankCurrency, UpdateSourceTrigger=LostFocus,Mode=Twoway}">

C#代码

public KeyValuePair<string, bankCurrencyObject>? SelectedBankCurrency
    {
        get { return _selectedCurrency; }
        set
        {
                MessageBoxResult result = MessageBox.Show("Are you sure you want to change the currency?",
                       "Warning",
                       MessageBoxButton.OKCancel,
                       MessageBoxImage.Question);

                if (result == MessageBoxResult.Cancel)
                {
                    return;
                }
                else
                {
                    //set values
                }
   }
   }

尝试使用selectionChanged事件但这不起作用，

  private void Combobox_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        if (DataContext == null)
            return;
        var combo = (sender as ComboBox);

        if (combo != null && combo.IsDropDownOpen)
        {
            combo.IsDropDownOpen = false;
            var binding = combo.GetBindingExpression(ComboBox.SelectedItemProperty);

            binding.UpdateSource();
            binding.UpdateTarget();
        }
    }`

Answer 1

您可以在 SelectionChanged 事件中执行此操作。

selectedItem 字段会跟踪先前选择的项目，以便在货币没有变化时不会显示 MessageBox。如果所选项目已更改，它将在显示 MessageBox 之前隐藏 DropDown 菜单。然后，如果用户单击“取消”，它将恢复更改，否则会将当前选择存储在 selectedItem 中以便将来进行比较。

private object selectedItem = null;

private void Currency_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
    if (Currency.SelectedItem == selectedItem)
        return;

    Currency.IsDropDownOpen = false;

    MessageBoxResult result = MessageBox.Show("Are you sure you want to change the currency?",
           "Warning",
           MessageBoxButton.OKCancel,
           MessageBoxImage.Question);

    if (result == MessageBoxResult.Cancel)
        Currency.SelectedItem = selectedItem;
    else
        selectedItem = Currency.SelectedItem;
}