|ZYCWPF| Interaction.Triggers中的EventTrigger中的KeyDown如何将KeyEventArgs进行传参，谢谢

[javamy010]

如我有

<TextBox Height="30" Name="txtUserName" Width="160" FontSize="20" VerticalContentAlignment="Center" Text="{Binding UserNme}">
    <i:Interaction.Triggers>
        <i:EventTrigger EventName="KeyDown">
            <i:InvokeCommandAction Command="{Binding OnUserNameKeyDown}" CommandParameter="？？？" />
        </i:EventTrigger>
    </i:Interaction.Triggers>
</TextBox>

       public ICommand OnUserNameKeyDown { get; set; }
       /// <summary>
       /// 绑定事件
        /// </summary>
        void BindEvent()
        {
            this.OnUserNameKeyDown = new DelegateCommand<KeyEventArgs>(UserNameKeyDown);
        }
        void UserNameKeyDown(KeyEventArgs e)
        {
            if (e.Key == Key.Enter)
            {
                Login(null);
            }
        }

在XAML中如何绑定这个KeyDown的Event参数
谢谢

[javamy010]

UP。。。。。。

[jshi123]

据我所知InvokeCommandAction无法传这个事件参数。 你可以直接用CallMethodAction:

    <TextBox Height="30" Name="txtUserName" Width="160" FontSize="20" VerticalContentAlignment="Center" Text="{Binding UserNme}">
        <i:Interaction.Triggers>
            <i:EventTrigger EventName="KeyDown">
                <ei:CallMethodAction TargetObject="{Binding}" MethodName="UserNameKeyDown" />
            </i:EventTrigger>
        </i:Interaction.Triggers>
    </TextBox>

UserNameKeyDown要改成标准的事件处理方法的形式：

	public void UserNameKeyDown(object sender, KeyEventArgs e)
	{
		if (e.Key == Key.Enter)
		{
			Login(null);
		}
	}

当然模仿InvokeCommandAction自己写一个可以传参的action也很容易：

	public class InvokeEventCommand : TriggerAction<DependencyObject>
	{
		public static readonly DependencyProperty CommandProperty = 
			DependencyProperty.Register("Command", typeof(ICommand), typeof(InvokeEventCommand));

		public ICommand Command
		{
			get { return (ICommand)GetValue(CommandProperty); }
			set { SetValue(CommandProperty, value); }
		}

		protected override void Invoke(object parameter)
		{
			if (Command != null && Command.CanExecute(parameter))
				Command.Execute(parameter);
		}
	}

前台调用：

    <TextBox Height="30" Name="txtUserName" Width="160" FontSize="20" VerticalContentAlignment="Center" Text="{Binding UserNme}">
        <i:Interaction.Triggers>
            <i:EventTrigger EventName="KeyDown">
                <local:InvokeEventCommand Command="{Binding OnUserNameKeyDown}" />
            </i:EventTrigger>
        </i:Interaction.Triggers>
    </TextBox>

还是一种方法是做一个attached propety, 这样可以直接写在TextBox标记里，不必用Interaction.Triggers绕个圈子：

	public class CommandAction
	{
		public static DependencyProperty KeyDownProperty =
			DependencyProperty.RegisterAttached("KeyDown", typeof(ICommand), typeof(CommandAction),
												new UIPropertyMetadata(KeyDownCommandChanged));

		public static void SetKeyDown(UIElement target, bool value)
		{
			target.SetValue(KeyDownProperty, value);
		}

		private static void KeyDownCommandChanged(DependencyObject target, DependencyPropertyChangedEventArgs e)
		{
			var textbox = target as TextBox;
			if (textbox == null)
				throw new InvalidOperationException("This behavior can be attached to TextBox only.");
			if (e.NewValue != null && e.OldValue == null)
				textbox.KeyDown +=TextboxKeyDown;
			else if (e.NewValue == null && e.OldValue != null)
				textbox.KeyDown -= TextboxKeyDown;
		}

		static void TextboxKeyDown(object sender, KeyEventArgs e)
		{
			var textbox = (TextBox) sender; 
			var command = (ICommand)textbox.GetValue(KeyDownProperty);
			command.Execute(e);
		}
	}

前台：

    <TextBox Height="30" Name="txtUserName" Width="160" FontSize="20" VerticalContentAlignment="Center" Text="{Binding UserNme}" 
        local:CommandAction.KeyDown="{Binding OnUserNameKeyDown}"/>

[机器人]

ls 回答的很好，学习了。 另，MvvmLight 已经用 PassEventArgsToCommand 封装了。

  
 xmlns:gmc="clr-namespace:GalaSoft.MvvmLight.Command;assembly=GalaSoft.MvvmLight.Extras.WPF4"
 ...

<i:Interaction.Triggers>
    <i:EventTrigger EventName="KeyDown">
      <gmc:EventToCommand PassEventArgsToCommand="True" Command="{Binding KeyDownCommand}" />
    </i:EventTrigger>
  </i:Interaction.Triggers>