Add Point On Click

View model

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

namespace ViewModelsSamples.Events.AddPointOnClick;

public partial class ViewModel : ObservableObject
{
    public ISeries[] SeriesCollection { get; set; } =
        new ISeries[]
        {
            new LineSeries<ObservablePoint>
            {
                Values = new ObservableCollection<ObservablePoint>
                {
                    new(0, 5),
                    new(3, 8),
                    new(7, 9)
                },
                Fill = null,
                DataPadding = new LiveChartsCore.Drawing.LvcPoint(5, 5)
            }
        };

    [RelayCommand]
    public void PointerDown(PointerCommandArgs args)
    {
        var chart = (ICartesianChartView<SkiaSharpDrawingContext>)args.Chart;
        var values = (ObservableCollection<ObservablePoint>)SeriesCollection[0].Values!;

        // 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.
        values.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">
  <UserControl.DataContext>
    <vms:ViewModel/>
  </UserControl.DataContext>
  <lvc:CartesianChart
      x:Name="chart"
      Series="{Binding SeriesCollection}"
      PointerPressedCommand="{Binding PointerDownCommand}"
      TooltipPosition="Hidden">
  </lvc:CartesianChart>
</UserControl>

View code behind

using Avalonia.Controls;
using Avalonia.Markup.Xaml;

namespace AvaloniaSample.Events.AddPointOnClick;

public partial class View : UserControl
{
    public View()
    {
        InitializeComponent();
    }

    private void InitializeComponent()
    {
        AvaloniaXamlLoader.Load(this);
    }
}