// attach even in chrome, which extends plotmodel.
this.MouseDown += OnMouseDown;
this.MouseMove += OnMouseMove;
this.MouseUp += OnMouseUp;
public MouseTool MouseTool{get;set;} // moues tool property.

//-------------------------------------------
// inside the chrome. and this mouse tool can be any tool people create.
private void OnMouseDown(object sender, OxyMouseDownEventArgs e) {
            if (_mouseTool != null) {
                _mouseTool.OnMouseDown(this, e);
            }
        }

//--------------------------------------------
// example of delete mouse tool, click an annotation, remove it from annotations collection.

public class DeleteAnnotationMouseTool : MouseTool {
     public override void OnMouseDown(ChromeModel chrome, OxyMouseDownEventArgs e) {
        HitTestResult hitResult;
        ScreenPoint screenPoint = e.Position;
        
        foreach (Annotation a in chrome.Annotations) {
            // here needs HitTest. 
            hitResult = a.HitTest(screenPoint, HIT_TEST_TOLERANCE);
            if (hitResult != null) {
                // add to collection for later to delete.
                break;
            }
        }
        // delete annotation.
    }
}

Public MouseTool MouseTool{get;set;} // include this property in PlotModel.
 public void HandleMouseDown(object sender, OxyMouseDownEventArgs e)
        {
            // handle mouse tool first.
            // pass plotmodel instead of plotControl. so mouse tool could modify annotations collection or other plotmodel's properties.
            if (mouseTool!=null){
               mouseTool.OnMouseDown(this, e)); 
               if(e.handled) return;
            }
            
            // Revert the order to handle the top-level elements first
            foreach (var element in this.GetElements().Reverse())
            {
                var uiElement = element as UIPlotElement;
                if (uiElement == null)
                {
                    continue;
                }

                var result = uiElement.HitTest(e.Position, MouseHitTolerance);
                if (result != null)
                {
                    e.HitTestResult = result;
                    uiElement.OnMouseDown(sender, e);
                    if (e.Handled)
                    {
                        this.currentMouseEventElement = uiElement;
                    }
                }

                if (e.Handled)
                {
                    break;
                }
            }

            if (!e.Handled)
            {
                this.OnMouseDown(sender, e);
            }
        }

<Style x:Key="cbSeriesCheckboxes" TargetType="{x:Type CheckBox}" >
    <Setter Property="MinHeight" Value="16" />
    <Setter Property="IsEnabled" Value="True" />
</Style>

<Style x:Key="AreaSeriesSampleStyle" TargetType="{x:Type oxy:AreaSeries}">
    <Setter Property="LineStyle" Value="Solid" />
    <Setter Property="StrokeThickness" Value="1" />
    <Setter Property="DataFieldY2" Value="Y2" />
    <Setter Property="DataFieldX2" Value="X" />
    <Setter Property="Visibility" Value="Collapsed" />
    <Setter Property="Title" Value="{Binding ElementName=cbAreaSeriesSample, Path=Content}" />
    <Style.Triggers>
        <MultiDataTrigger>
            <MultiDataTrigger.Conditions>
                <Condition Binding="{Binding ElementName=cbAreaSeriesSample, Path=IsChecked}" Value="True"/>
                <Condition Binding="{Binding ElementName=cbAreaSeriesSample, Path=IsVisible}" Value="True"/>
            </MultiDataTrigger.Conditions>
            <Setter Property="Visibility" Value="Visible" />
        </MultiDataTrigger>
    </Style.Triggers>
    <Style.Triggers>
        <Trigger Property="Tag" Value="0">
            <Setter Property="Fill" Value="#4490EE90" />
            <Setter Property="Color" Value="LightGreen" />
        </Trigger>
        <Trigger Property="Tag" Value="1">
            <Setter Property="Fill" Value="#44FFD700" />
            <Setter Property="Color" Value="Gold" />
        </Trigger>
        <Trigger Property="Tag" Value="2">
            <Setter Property="Fill" Value="#44FFA500" />
            <Setter Property="Color" Value="Orange" />
        </Trigger>
        <Trigger Property="Tag" Value="3">
            <Setter Property="Fill" Value="#445F9EA0" />
            <Setter Property="Color" Value="CadetBlue" />
        </Trigger>
    </Style.Triggers>
</Style>
<Style x:Key="cbAreaSeriesSample" TargetType="{x:Type CheckBox}" BasedOn="{StaticResource cbSeriesCheckboxes}">
    <Setter Property="Foreground" Value="Green" />
    <Setter Property="Background" Value="WhiteSmoke" />
</Style>

<Style x:Key="StepSeriesSampleStyle" TargetType="{x:Type my:StairStepSeries}">
    <Setter Property="Color" Value="Blue" />
    <Setter Property="Title" Value="{Binding ElementName=cbStepSeriesSample, Path=Content}" />
    <Style.Triggers>
        <MultiDataTrigger>
            <MultiDataTrigger.Conditions>
                <Condition Binding="{Binding ElementName=cbStepSeriesSample, Path=IsChecked}" Value="True"/>
                <Condition Binding="{Binding ElementName=cbStepSeriesSample, Path=IsVisible}" Value="True"/>
            </MultiDataTrigger.Conditions>
            <Setter Property="Visibility" Value="Visible" />
        </MultiDataTrigger>
    </Style.Triggers>
</Style>
<Style x:Key="cbStepSeriesSample" TargetType="{x:Type CheckBox}" BasedOn="{StaticResource cbSeriesCheckboxes}">
    <Setter Property="Foreground" Value="Blue" />
    <Setter Property="Background" Value="WhiteSmoke" />
</Style>

<Style x:Key="LineSeriesSampleStyle" TargetType="{x:Type oxy:LineSeries}" >
    <Setter Property="LineStyle" Value="Solid" />
    <Setter Property="StrokeThickness" Value="3" />
    <Setter Property="Visibility" Value="Collapsed" />
    <Setter Property="CanTrackerInterpolatePoints" Value="False" />
    <Setter Property="Color" Value="Brown" />
    <Setter Property="Title" Value="{Binding ElementName=cbLineSeriesSample, Path=Content}" />
    <Style.Triggers>
        <MultiDataTrigger>
            <MultiDataTrigger.Conditions>
                <Condition Binding="{Binding ElementName=cbLineSeriesSample, Path=IsChecked}" Value="True"/>
                <Condition Binding="{Binding ElementName=cbLineSeriesSample, Path=IsVisible}" Value="True"/>
            </MultiDataTrigger.Conditions>
            <Setter Property="Visibility" Value="Visible" />
        </MultiDataTrigger>
    </Style.Triggers>
</Style>
<Style x:Key="cbLineSeriesSample" TargetType="{x:Type CheckBox}" BasedOn="{StaticResource cbSeriesCheckboxes}">
    <Setter Property="Foreground" Value="Brown" />
    <Setter Property="Background" Value="WhiteSmoke" />
</Style>




<StackPanel x:Name="Graphs" Orientation="Vertical">
    <oxy:Plot x:Name="TopPlot" Style="{StaticResource Plot}" MinHeight="380" Height="400" >
        <oxy:Plot.Axes>
            <oxy:DateTimeAxis Style="{StaticResource DateTimeAxis}"/>
            <oxy:LinearAxis Style="{StaticResource LinearAxis}"/> 
        </oxy:Plot.Axes>
        <oxy:AreaSeries Style="{StaticResource AreaSeriesSampleStyle}" ItemsSource="{Binding AreaSeriesData0}" Tag="0"/>
        <oxy:AreaSeries Style="{StaticResource AreaSeriesSampleStyle}" ItemsSource="{Binding AreaSeriesData1}" Tag="1"/>
        <oxy:AreaSeries Style="{StaticResource AreaSeriesSampleStyle}" ItemsSource="{Binding AreaSeriesData2}" Tag="2"/>
        <oxy:AreaSeries Style="{StaticResource AreaSeriesSampleStyle}" ItemsSource="{Binding AreaSeriesData3}" Tag="3"/>
        <my:StairStepSeries Style="{StaticResource StepSeriesSampleStyle}" ItemsSource="{Binding StepSeriesSampleData}"/>
        <oxy:LineSeries Style="{StaticResource LineSeriesSampleStyle}" ItemsSource="{Binding LineSeriesSampleData}"/>
    </oxy:Plot>
</StackPanel>

<StackPanel>
    <CheckBox x:Name="cbAreaSeriesSample" Style="{StaticResource cbAreaSeriesSample}" Content="Area Series" />
    <CheckBox x:Name="cbStepSeriesSample" Style="{StaticResource cbStepSeriesSample}" Content="StairStep Series" IsChecked="True"/>
    <CheckBox x:Name="cbLineSeriesSample" Style="{StaticResource cbLineSeriesSample}" Content="Line Series" IsChecked="False"  />
</StackPanel>

/// <summary>
///     Refreshes the custom legend based on the axes and series in the PlotModel.
/// </summary>
private void UpdateCustomLegend()
{
    uiSeriesLegendLayout.Controls.Clear();
    uiAxesLegendLayout.Controls.Clear();

    foreach (LineSeries s in PlotModel.Series.OfType<LineSeries>().OrderBy(s => s.Title))
    {
        var seriesColorButton = new Button
        {
            AutoSize = true,
            BackColor = s.Color.ToColor(),
            FlatStyle = FlatStyle.Flat,
            Size = new Size(30, 15),
            Tag = s.Tag,
            UseVisualStyleBackColor = false
        };
        seriesColorButton.Click += (sender, args) =>
        {
            using (var d = new ColorDialog())
            {
                d.Color = s.Color.ToColor();
                if (d.ShowDialog() != DialogResult.OK)
                    return;

                s.Color = d.Color.ToOxyColor();
                ((Button) sender).BackColor = d.Color;
                PlotModel.InvalidatePlot(false);
            }
        };

        var seriesVisibilityCheckBox = new CheckBox
        {
            AutoSize = true,
            Checked = s.IsVisible,
            Tag = s.Tag,
            Text = s.Title
        };
        seriesVisibilityCheckBox.CheckedChanged += (sender, args) =>
        {
            s.IsVisible = ((CheckBox) sender).Checked;
            PlotModel.InvalidatePlot(false);
        };

        uiSeriesLegendLayout.Controls.Add(seriesColorButton);
        uiSeriesLegendLayout.Controls.Add(seriesVisibilityCheckBox);
        uiSeriesLegendLayout.SetFlowBreak(seriesVisibilityCheckBox, true);
    }

    var seriesSelectAllCheckBox = new CheckBox
    {
        AutoSize = true,
        Checked = true,
        Text = "Select All"
    };
    seriesSelectAllCheckBox.CheckedChanged += (sender, args) =>
    {
        foreach (CheckBox cb in uiSeriesLegendLayout.Controls.OfType<CheckBox>())
            cb.Checked = ((CheckBox) sender).Checked;
    };

    uiSeriesLegendLayout.Controls.Add(seriesSelectAllCheckBox);

    var hideLinkedSeriesCheckBox = new CheckBox
    {
        AutoSize = true,
        Checked = false,
        Text = "Hide Linked Series"
    };

    foreach (LinearAxis a in PlotModel.Axes.OfType<LinearAxis>())
    {
        var axisVisibilityCheckBox = new CheckBox
        {
            AutoSize = true,
            Checked = a.IsAxisVisible,
            Tag = a.Tag,
            Text = a.Title
        };
        axisVisibilityCheckBox.CheckedChanged += (sender, args) =>
        {
            a.IsAxisVisible = ((CheckBox) sender).Checked;
            PlotModel.InvalidatePlot(false);

            if (!hideLinkedSeriesCheckBox.Checked)
                return;

            foreach (
                LineSeries s in
                    PlotModel.Series.OfType<LineSeries>()
                             .Where(s => s.YAxisKey == a.Key || s.XAxisKey == a.Key))
            {
                s.IsVisible = a.IsAxisVisible;
                uiSeriesLegendLayout.Controls.OfType<CheckBox>()
                                    .Single(cb => cb.Tag == s.Tag)
                                    .Checked = s.IsVisible;
            }
        };

        uiAxesLegendLayout.Controls.Add(axisVisibilityCheckBox);
        uiAxesLegendLayout.SetFlowBreak(axisVisibilityCheckBox, true);
    }

    var axisSelectAllCheckBox = new CheckBox
    {
        AutoSize = true,
        Checked = true,
        Text = "Select All"
    };
    axisSelectAllCheckBox.CheckedChanged += (sender, args) =>
    {
        foreach (
            CheckBox cb in
                uiAxesLegendLayout.Controls.OfType<CheckBox>()
                                  .Where(cb => cb != hideLinkedSeriesCheckBox))
            cb.Checked = ((CheckBox) sender).Checked;
    };

    uiAxesLegendLayout.Controls.Add(axisSelectAllCheckBox);
    uiAxesLegendLayout.Controls.Add(hideLinkedSeriesCheckBox);
}