Add Point On Click

sample image

View model

using System.Collections.ObjectModel;
using CommunityToolkit.Mvvm.ComponentModel;
using LiveChartsCore;
using LiveChartsCore.Defaults;
using LiveChartsCore.SkiaSharpView;

namespace ViewModelsSamples.Events.AddPointOnClick;

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

        Data = data;

        SeriesCollection = new ISeries[]
        {
            new LineSeries<ObservablePoint>
            {
                Values = data,
                Fill = null,
                DataPadding = new LiveChartsCore.Drawing.LvcPoint(5, 5)
            }
        };
    }

    public ObservableCollection<ObservablePoint> Data { get; set; }

    public ISeries[] SeriesCollection { get; set; }
}

HTML

@page "/Events/AddPointOnClick"
@using LiveChartsCore.Defaults
@using LiveChartsCore.Drawing
@using LiveChartsCore.SkiaSharpView.Blazor
@using ViewModelsSamples.Events.AddPointOnClick

<CartesianChart
	@ref="_chart"
	Series="ViewModel.SeriesCollection"
	OnPointerDownCallback="onPointerDown"
	TooltipPosition="LiveChartsCore.Measure.TooltipPosition.Hidden">
</CartesianChart>

@code {
	private CartesianChart _chart;

	public ViewModel ViewModel { get; set; } = new();

	private void onPointerDown(PointerEventArgs e)
	{
        // scales the UI coordinates to the corresponding data in the chart.
        // ScaleUIPoint returns an array of double
        var scaledPoint = _chart.ScaleUIPoint(new LvcPoint((float)e.OffsetX, (float)e.OffsetY));

        // where the X coordinate is in the first position
        var x = scaledPoint[0];

        // and the Y coordinate in the second position
        var y = scaledPoint[1];

        // finally add the new point to the data in our chart.
        ViewModel.Data.Add(new ObservablePoint(x, y));
	}
}