Question

当用户在TextBox中按Enter键时，我想在viewmodel中执行命令。该命令在绑定到按钮时有效。

<Button Content="Add" Command="{Binding Path=AddCommand}" />

但是我不能从TextBox开始工作。我尝试了一个Inputbinding，但它没有用。

<TextBox.InputBindings>
    <KeyBinding Command="{Binding Path=AddCommand}" Key="Enter"/>
</TextBox.InputBindings>

我还尝试将工作按钮设置为默认值，但按下输入时不会执行。

感谢您的帮助。

Answer 1

我知道我迟到了，但我让这个为我工作。尝试使用Key="Return"代替Key="Enter"

以下是完整示例

<TextBox Text="{Binding FieldThatIAmBindingToo, UpdateSourceTrigger=PropertyChanged}">
    <TextBox.InputBindings>
        <KeyBinding Command="{Binding AddCommand}" Key="Return" />
    </TextBox.InputBindings>
</TextBox>

确保在绑定中使用UpdateSourceTrigger=PropertyChanged，否则在焦点丢失之前不会更新属性，按Enter键不会失去焦点......

希望这有用！

Answer 2

您可能没有将命令设为属性，而是字段。它只能绑定到属性。将AddCommand更改为属性，它将起作用。（您的XAML对我来说很适合使用属性而不是命令的字段 - ＆gt;不需要任何代码！）

Answer 3

这是我为此创建的附加依赖项属性。它的优点是确保在命令触发之前将文本绑定更新回ViewModel（对于不支持属性更改的更新源触发器的silverlight非常有用）。

public static class EnterKeyHelpers
{
    public static ICommand GetEnterKeyCommand(DependencyObject target)
    {
        return (ICommand)target.GetValue(EnterKeyCommandProperty);
    }

    public static void SetEnterKeyCommand(DependencyObject target, ICommand value)
    {
        target.SetValue(EnterKeyCommandProperty, value);
    }

    public static readonly DependencyProperty EnterKeyCommandProperty =
        DependencyProperty.RegisterAttached(
            "EnterKeyCommand",
            typeof(ICommand),
            typeof(EnterKeyHelpers),
            new PropertyMetadata(null, OnEnterKeyCommandChanged));

    static void OnEnterKeyCommandChanged(DependencyObject target, DependencyPropertyChangedEventArgs e)
    {
        ICommand command = (ICommand)e.NewValue;
        FrameworkElement fe = (FrameworkElement)target;
        Control control = (Control)target;
        control.KeyDown += (s, args) =>
        {
            if (args.Key == Key.Enter)
            {
                // make sure the textbox binding updates its source first
                BindingExpression b = control.GetBindingExpression(TextBox.TextProperty);
                if (b != null)
                {
                    b.UpdateSource();
                }
                command.Execute(null);
            }
        };
    }
}

你这样使用它：

<TextBox 
    Text="{Binding Answer, Mode=TwoWay}" 
    my:EnterKeyHelpers.EnterKeyCommand="{Binding SubmitAnswerCommand}"/>

Answer 4

您需要定义Gesture而不是KeyBinding的Key属性：

<TextBox.InputBindings>
    <KeyBinding Gesture="Enter" Command="{Binding AddCommand}"/>
</TextBox.InputBindings>

Answer 5

除了Mark Heath的回答之外，我通过这种方式实现Command Parameter附加属性，使课程更进了一步;

public static class EnterKeyHelpers
{
        public static ICommand GetEnterKeyCommand(DependencyObject target)
        {
            return (ICommand)target.GetValue(EnterKeyCommandProperty);
        }

        public static void SetEnterKeyCommand(DependencyObject target, ICommand value)
        {
            target.SetValue(EnterKeyCommandProperty, value);
        }

        public static readonly DependencyProperty EnterKeyCommandProperty =
            DependencyProperty.RegisterAttached(
                "EnterKeyCommand",
                typeof(ICommand),
                typeof(EnterKeyHelpers),
                new PropertyMetadata(null, OnEnterKeyCommandChanged));


        public static object GetEnterKeyCommandParam(DependencyObject target)
        {
            return (object)target.GetValue(EnterKeyCommandParamProperty);
        }

        public static void SetEnterKeyCommandParam(DependencyObject target, object value)
        {
            target.SetValue(EnterKeyCommandParamProperty, value);
        }

        public static readonly DependencyProperty EnterKeyCommandParamProperty =
            DependencyProperty.RegisterAttached(
                "EnterKeyCommandParam",
                typeof(object),
                typeof(EnterKeyHelpers),
                new PropertyMetadata(null));

        static void OnEnterKeyCommandChanged(DependencyObject target, DependencyPropertyChangedEventArgs e)
        {
            ICommand command = (ICommand)e.NewValue;
            Control control = (Control)target;
            control.KeyDown += (s, args) =>
            {
                if (args.Key == Key.Enter)
                {
                    // make sure the textbox binding updates its source first
                    BindingExpression b = control.GetBindingExpression(TextBox.TextProperty);
                    if (b != null)
                    {
                        b.UpdateSource();
                    }
                    object commandParameter = GetEnterKeyCommandParam(target);
                    command.Execute(commandParameter);
                }
            };
        }
    }

用法：

<TextBox Text="{Binding Answer, Mode=TwoWay}" 
    my:EnterKeyHelpers.EnterKeyCommand="{Binding SubmitAnswerCommand}"
    my:EnterKeyHelpers.EnterKeyCommandParam="your parameter"/>

在TextBox中输入时执行viewmodels命令

5 个答案: