WPF中LiveCharts CartesianChart鼠标左右键按下事件绑定失败求助

• WPF原生事件（如MouseLeftButtonDown）无法直接绑定ViewModel中的ICommand，你当前的XAML写法混淆了事件绑定与命令绑定的规则，这是核心错误。
• ViewModel中ChartMouseRightButtonDownCommand的代码未闭合，存在语法错误，导致编译失败。
• Array.Append()不会修改原数组，它返回新数组，你未将返回值重新赋值给原变量，数据不会实际更新。

1. 安装行为库 #

要在ViewModel中处理控件事件，需借助行为库实现事件转命令。安装NuGet包Microsoft.Xaml.Behaviors.Wpf（官方替代旧版System.Windows.Interactivity）。

2. 修改XAML代码 #

添加行为命名空间，通过EventTrigger和InvokeCommandAction将事件绑定到ViewModel命令：

xmlns:i="http://schemas.microsoft.com/xaml/behaviors"

<lvc:CartesianChart
    x:Name="LibSpeed"
    DockPanel.Dock="Top"
    Series="{Binding SeriesCollection}"
    XAxes="{Binding XAxes}"
    YAxes="{Binding YAxes}">
    <i:Interaction.Triggers>
        <i:EventTrigger EventName="MouseLeftButtonDown">
            <i:InvokeCommandAction Command="{Binding ChartMouseLeftButtonDownCommand}"
                                   PassEventArgsToCommand="True"/>
        </i:EventTrigger>
        <i:EventTrigger EventName="MouseRightButtonDown">
            <i:InvokeCommandAction Command="{Binding ChartMouseRightButtonDownCommand}"
                                   PassEventArgsToCommand="True"/>
        </i:EventTrigger>
    </i:Interaction.Triggers>
</lvc:CartesianChart>

3. 修正ViewModel代码 #

补全语法错误，修复数组更新逻辑，同时注意事件参数类型：

private ICommand chartMouseLeftButtonDownCommand;
public ICommand ChartMouseLeftButtonDownCommand
{
    get => chartMouseLeftButtonDownCommand ?? (chartMouseLeftButtonDownCommand = new CommandHandler((parameter) =>
    {
        if (parameter is MouseButtonEventArgs args)
        {
            // 获取相对于图表的鼠标位置，而非全局位置
            var mousePosition = args.GetPosition(LibSpeed);
            var x = mousePosition.X;
            var y = mousePosition.Y;

            // 注意：直接用像素坐标匹配数据值可能不准确，建议用LiveCharts API转换
            // 示例：var chart = (CartesianChart)args.Source;
            // var dataX = chart.AxisX[0].ToPlotArea(x);
            // var dataY = chart.AxisY[0].ToPlotArea(y);

            if (lutLibrary.XValuesReduced.Contains(x) && lutLibrary.YValuesReduced.Contains(y))
            {
                lutLibrary.YValuesReduced = lutLibrary.YValuesReduced.Where(val => val != y).ToArray();
                lutLibrary.XValuesReduced = lutLibrary.XValuesReduced.Where(val => val != x).ToArray();
            }
        }
    }, () => true));
}

private ICommand chartMouseRightButtonDownCommand;
public ICommand ChartMouseRightButtonDownCommand
{
    get => chartMouseRightButtonDownCommand ?? (chartMouseRightButtonDownCommand = new CommandHandler((parameter) =>
    {
        if (parameter is MouseButtonEventArgs args)
        {
            var mousePosition = args.GetPosition(LibSpeed);
            var xValue = mousePosition.X;
            var yValue = mousePosition.Y;

            // 修复数组更新：重新赋值Append返回的新数组
            lutLibrary.YValuesReduced = lutLibrary.YValuesReduced.Append(yValue).ToArray();
            lutLibrary.XValuesReduced = lutLibrary.XValuesReduced.Append(xValue).ToArray();

            MainWindow_ViewModel.initPoints();
        }
    }, () => true));
}

4. 额外提示 #

• 直接用像素坐标匹配数据值精度低，建议使用LiveCharts的ToPlotArea/ToCoordinate方法将像素坐标转换为实际数据值，再进行匹配。
• 确保ViewModel实现INotifyPropertyChanged接口，数据更新后图表才能自动刷新。

内容的提问来源于stack exchange，提问作者Kaiser