Im trying to render a vertical red line from the bottom to top of my y axis , i have a specific wavelength in the x axis so when the user use the slider it will stop and take that specific wavelength.

Here is my code :

         public PlotViewModel()
        {
            InitializeRenderingLoop();

            // Initialize SpectralPlotModel
            SpectralPlotModel = new PlotModel
            {
                Title = "Data from Socket",
                Background = OxyColors.Transparent,
                TextColor = OxyColors.White,
                PlotAreaBorderColor = OxyColors.White
            };

            SpectralPlotModel.Axes.Add(new LinearAxis
            {
                Position = AxisPosition.Bottom,
                Title = "Wavelength",
                TitleColor = OxyColors.White,
                AxislineColor = OxyColors.White,
                TextColor = OxyColors.White,
                StringFormat = "0.###",
            });

            SpectralPlotModel.Axes.Add(new LinearAxis
            {
                Position = AxisPosition.Left,
                Title = "Data",
                TitleColor = OxyColors.White,
                AxislineColor = OxyColors.White,
                TextColor = OxyColors.White,
                StringFormat = "0.###",
                Minimum = 0,
                Maximum = 5
            });


            SpectralPlotModel.Series.Add(new LineSeries
            {
                Title = "Data",
                Color = OxyColors.White,
                MarkerFill = OxyColors.White,
                MarkerType = MarkerType.None,
                LineStyle = LineStyle.Solid,
                StrokeThickness = 2
            });

            SpectralPlotModel.Series.Add(new LineSeries
            {
                Title = "Red Line",
                Color = OxyColors.Red,
                MarkerFill = OxyColors.Red,
                MarkerType = MarkerType.Cross,
                LineStyle = LineStyle.Solid,
                StrokeThickness = 15,
            });

        }

and the function logic :

        public double WavelengthSliderValue
        {
            get => _wavelengthSliderValue;
            set
            {
                if (_wavelengthSliderValue != value)
                {
                    _wavelengthSliderValue = value;
                    OnPropertyChanged();
                    UpdateRedLine();
                }
            }
        }


        public void UpdateRedLine()
        {

            if (SpectralPlotModel != null && SpectralPlotModel.Series.Count > 1)
            {
                var redLineSeries = SpectralPlotModel.Series[1] as LineSeries;

                if (redLineSeries != null)
                {
                    var selectedWavelength = WavelengthSliderValue;
                    Debug.Print("Wavelength : " + selectedWavelength);

                    // Clear existing points
                    redLineSeries.Points.Clear();

                    // Ensure the axis limits are correct
                    var yAxis = SpectralPlotModel.Axes[1];
                    redLineSeries.Points.Add(new DataPoint(selectedWavelength, yAxis.Minimum)); // Min Y
                    redLineSeries.Points.Add(new DataPoint(selectedWavelength, yAxis.Maximum)); // Max Y
                    SpectralPlotModel.InvalidatePlot(true);
                }
                else
                {

                    Debug.Write("No red line series found");
                }
            }
        }

My xaml files (Im using MVVM) :

        <Border Grid.Row="0">
            <oxy:PlotView Name="SpectralPlot"
                          Width="Auto"
                          Height="Auto"
                          HorizontalAlignment="Stretch"
                          VerticalAlignment="Stretch"
                          Background="Transparent"
                          Model="{Binding SpectralPlotModel}" />
            <Slider Minimum="1546"
                    Maximum="1558"
                    Value="{Binding WavelengthSliderValue}"
                    VerticalAlignment="Center"
                    HorizontalAlignment="Stretch"
                    Margin="10,0,10,0" />

Inside UpdateRedLine i take correctly the Wavelength so the number i take is fine but for some reason it does not render my red line at all .

Do i set it wrong?

Thanks .