Add Point On Click

View model

using System.Collections.ObjectModel;
using CommunityToolkit.Mvvm.Input;
using LiveChartsCore.Defaults;
using LiveChartsCore.Kernel.Events;
using LiveChartsCore.Kernel.Sketches;

namespace ViewModelsSamples.Events.AddPointOnClick;

public partial class ViewModel
{
    public ObservableCollection<ObservablePoint> Points { get; set; } =
        [
            new(0, 5),
            new(3, 8),
            new(7, 9)
        ];

    [RelayCommand]
    public void PointerDown(PointerCommandArgs args)
    {
        var chart = (ICartesianChartView)args.Chart;

        // scales the UI coordinates to the corresponding data in the chart.
        var scaledPoint = chart.ScalePixelsToData(args.PointerPosition);

        // finally add the new point to the data in our chart.
        Points.Add(new ObservablePoint(scaledPoint.X, scaledPoint.Y));
    }
}

XAML

<UserControl
    x:Class="AvaloniaSample.Events.AddPointOnClick.View"
    xmlns="https://github.com/avaloniaui"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:lvc="using:LiveChartsCore.SkiaSharpView.Avalonia"
    xmlns:vms="using:ViewModelsSamples.Events.AddPointOnClick"
    x:DataType="vms:ViewModel">

    <UserControl.DataContext>
        <vms:ViewModel/>
    </UserControl.DataContext>

    <lvc:CartesianChart
        PointerPressedCommand="{Binding PointerDownCommand}"
        TooltipPosition="Hidden">
        <lvc:CartesianChart.Series>
            <lvc:XamlLineSeries
                Values="{Binding Points}"
                Fill="{x:Null}"
                DataPadding="{lvc:Point '5,5'}"/>
        </lvc:CartesianChart.Series>
    </lvc:CartesianChart>

</UserControl>