Crosshairs

The [ObservableObject], [ObservableProperty] and [RelayCommand] attributes come from the CommunityToolkit.Mvvm package, you can read more about it here.

sample image

View model

using System.Collections.ObjectModel;
using CommunityToolkit.Mvvm.ComponentModel;
using LiveChartsCore;
using LiveChartsCore.SkiaSharpView;
using LiveChartsCore.SkiaSharpView.Painting;
using SkiaSharp;

namespace ViewModelsSamples.Axes.Crosshairs;

public partial class ViewModel : ObservableObject
{
    public ISeries[] Series { get; set; } =
    {
        new LineSeries<double>
        {
            Values = new ObservableCollection<double> { 200, 558, 458, 249, 457, 339, 587 },
        },
        new LineSeries<double>
        {
            Values = new ObservableCollection<double> { 210, 400, 300, 350, 219, 323, 618 },
        },
    };

    public Axis[] XAxes { get; set; } =
    {
        new Axis
        {
            CrosshairLabelsBackground = SKColors.DarkOrange.AsLvcColor(),
            CrosshairLabelsPaint = new SolidColorPaint(SKColors.DarkRed, 1),
            CrosshairPaint = new SolidColorPaint(SKColors.DarkOrange, 1),
            Labeler = value => value.ToString("N2")
        }
    };
    public Axis[] YAxes { get; set; } =
    {
        new Axis
        {
            CrosshairLabelsBackground = SKColors.DarkOrange.AsLvcColor(),
            CrosshairLabelsPaint = new SolidColorPaint(SKColors.DarkRed, 1),
            CrosshairPaint = new SolidColorPaint(SKColors.DarkOrange, 1),
            CrosshairSnapEnabled = true // snapping is also supported
        }
    };
}

XAML

<UserControl
    x:Class="UnoWinUISample.Axes.Crosshairs.View"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:lvc="using:LiveChartsCore.SkiaSharpView.WinUI"
    xmlns:vms="using:ViewModelsSamples.Axes.Crosshairs"
    mc:Ignorable="d">

    <UserControl.DataContext>
        <vms:ViewModel/>
    </UserControl.DataContext>
    <Grid>
        <lvc:CartesianChart
            Series="{Binding Series}"
            XAxes="{Binding XAxes}"
            YAxes="{Binding YAxes}">
        </lvc:CartesianChart>
    </Grid>
    
</UserControl>

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