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[英]How to detect if Enter event triggered by DropDown event for a ComboBox (c#)
[英]C# WPF editable Combobox how to detect Enter key
我使用 C# 和 WPF 和 MVVM
我有一个可编辑的组合框,这样用户不仅可以从列表中选择项目,还可以在组合框的文本字段中输入自己的文本
XAML:
<br>
<ComboBox IsEditable="True"<br>
IsTextSearchEnabled="True" <br>
IsTextSearchCaseSensitive="False"<br>
StaysOpenOnEdit="True"<br>
Text="{Binding TextEntered}"<br>
</ComboBox>
<br>
在绑定属性“TextEntered”中,我可以在调试器中看到用户输入的文本 - 但是如果用户按 ENTER 完成他的输入,这将不起作用。 那么当用户按下 Enter 时我该如何反应呢?
谢谢你
如果不想对 PropertyChanged 做出反应,可以将 UpdateSourceTrigger 设置为Explicit
<ComboBox IsEditable="True"
IsTextSearchEnabled="True"
IsTextSearchCaseSensitive="False"
StaysOpenOnEdit="True"
Text="{Binding TextEntered, UpdateSourceTrigger=Explicit}">
<ComboBox.InputBindings>
<KeyBinding Gesture="Enter"
Command="{Binding UpdateBindingOnEnterCommand}"
CommandParameter="{Binding RelativeSource={RelativeSource FindAncestor,AncestorType={x:Type ComboBox}}}"></KeyBinding>
</ComboBox.InputBindings>
并在执行命令时调用绑定的UpdateSource
public class UpdateBindingOnEnterCommand : ICommand
{
...
public void Execute(object parameter)
{
if (parameter is ComboBox control)
{
var prop = ComboBox.TextProperty;
var binding = BindingOperations.GetBindingExpression(control, prop);
binding?.UpdateSource();
}
}
...
}
您可以处理PreviewKeyDown
事件,例如使用附加行为:
public class EnterBehavior
{
public static ICommand GetCommand(UIElement element)
{
return (ICommand)element.GetValue(CommandProperty);
}
public static void SetCommand(UIElement element, ICommand value)
{
element.SetValue(CommandProperty, value);
}
public static readonly DependencyProperty CommandProperty =
DependencyProperty.RegisterAttached(
"Command",
typeof(ICommand),
typeof(EnterBehavior),
new PropertyMetadata(OnCommandChanged));
private static void OnCommandChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
UIElement element = (UIElement)d;
element.PreviewKeyDown += (ss, ee) =>
{
if (ee.Key == Key.Enter)
{
GetCommand(element)?.Execute(null);
}
};
}
}
示例用法:
<ComboBox IsEditable="True"
local:EnterBehavior.Command="{Binding YourCommandProperty}" ... />
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