Legend in .NET MAUI Chart (SfFunnelChart)

10 Jan 202515 minutes to read

The Legend provides a list of data points, helping to identify the corresponding data points in the chart. Here’s a detailed guide on how to define and customize the legend in the funnel chart.

Defining the legend

To define the legend in the chart, initialize the ChartLegend class and assign it to the Legend property.

<chart:SfFunnelChart ItemsSource="{Binding Data}" 
                     XBindingPath="XValue" 
                     YBindingPath="YValue">
    <chart:SfFunnelChart.Legend>
        <chart:ChartLegend/>
    </chart:SfFunnelChart.Legend>
</chart:SfFunnelChart>
SfFunnelChart chart = new SfFunnelChart()
{
    ItemsSource = new AdmissionViewModel().Data,
    XBindingPath = "XValue",
    YBindingPath = "YValue",
};

chart.Legend = new ChartLegend(); // Initialize the legend for the chart.
this.Content = chart;

Legend visibility

The visibility of the chart legend can be controlled using the IsVisible property. By default, the IsVisible property is set to true.

<chart:SfFunnelChart ItemsSource="{Binding Data}" 
                     XBindingPath="XValue"
                     YBindingPath="YValue">
    <chart:SfFunnelChart.Legend>
        <chart:ChartLegend IsVisible="True"/>
    </chart:SfFunnelChart.Legend>
</chart:SfFunnelChart>
SfFunnelChart chart = new SfFunnelChart()
{
    XBindingPath = "XValue",
    YBindingPath = "YValue",
    ItemsSource = new AdmissionViewModel().Data,
};

chart.Legend = new ChartLegend()
{ 
    IsVisible = true // Set the visibility of the chart legend.
};

this.Content = chart;

Customizing labels

The appearance of the legend label can be customized using the LabelStyle property.

  • TextColor – Gets or sets the color of the label.
  • FontFamily - Gets or sets the font family for the legend label.
  • FontAttributes - Gets or sets the font style for the legend label.
  • FontSize - Gets or sets the font size for the legend label.
  • Margin - Gets or sets the margin size of labels.
<chart:SfFunnelChart ItemsSource="{Binding Data}" 
                     XBindingPath="XValue"
                     YBindingPath="YValue">
    <chart:SfFunnelChart.Legend>
        <chart:ChartLegend>
            <chart:ChartLegend.LabelStyle>
                <chart:ChartLegendLabelStyle TextColor="Blue" Margin="5" FontSize="18"
                     FontAttributes="Bold" FontFamily="PlaywriteAR-Regular"/>
            </chart:ChartLegend.LabelStyle>
        </chart:ChartLegend>
    </chart:SfFunnelChart.Legend>
</chart:SfFunnelChart>
SfFunnelChart chart = new SfFunnelChart()
{
    XBindingPath = "XValue",
    YBindingPath = "YValue",
    ItemsSource = new ViewModel().Data,
};

ChartLegend legend = new ChartLegend(); // Initialize the legend.

// Define the label style for the legend.
ChartLegendLabelStyle labelStyle = new ChartLegendLabelStyle()
{
    TextColor = Colors.Blue,
    Margin = new Thickness(5),
    FontSize = 18,
    FontAttributes = FontAttributes.Bold,
    FontFamily = "PlaywriteAR-Regular"
};

legend.LabelStyle = labelStyle; // Set the label style for the legend.
chart.Legend = legend; // Set the legend for the chart.
this.Content = chart;

Legend labels customization support in Maui Chart

Legend icon

To specify the legend icon based on associate series type using the LegendIcon and change its type using ChartLegendIconType enum values.

<chart:SfFunnelChart ItemsSource="{Binding Data}" 
                     XBindingPath="XValue"  LegendIcon="Diamond"
                     YBindingPath="YValue">
    <chart:SfFunnelChart.Legend>
        <chart:ChartLegend/>
    </chart:SfFunnelChart.Legend>
</chart:SfFunnelChart>
SfFunnelChart chart = new SfFunnelChart()
{
    ItemsSource = new AdmissionViewModel().Data,
    XBindingPath = "XValue",
    YBindingPath = "YValue",
    LegendIcon = ChartLegendIconType.Diamond // Set the legend icon type.
};

chart.Legend = new ChartLegend();

this.Content = chart;

Placement

The legend can be positioned to the left, right, top, or bottom of the chart area using the Placement property in the ChartLegend class. The default placement is Top.

<chart:SfFunnelChart ItemsSource="{Binding Data}" 
                     XBindingPath="XValue"  
                     YBindingPath="YValue">
    <chart:SfFunnelChart.Legend>
        <chart:ChartLegend Placement="Bottom"/>
    </chart:SfFunnelChart.Legend>
</chart:SfFunnelChart>
SfFunnelChart chart = new SfFunnelChart()
{
    XBindingPath = "XValue",
    YBindingPath = "YValue",
    ItemsSource = new ViewModel().Data,
};
   
chart.Legend = new ChartLegend()
{ 
    Placement = LegendPlacement.Bottom // Set the legend placement.
};

this.Content = chart;

Toggle the series visibility

The visibility of segments in the funnel chart can be controlled by tapping the legend item using the ToggleSeriesVisibility property. The default value of ToggleSeriesVisibility is false.

<chart:SfFunnelChart ItemsSource="{Binding Data}" 
                     XBindingPath="XValue"         
                     YBindingPath="YValue">
    . . .
    <chart:SfFunnelChart.Legend>
        <chart:ChartLegend ToggleSeriesVisibility="True"/>
    </chart:SfFunnelChart.Legend>
    . . .
</chart:SfFunnelChart>
AdmissionViewModel viewModel = new();

SfFunnelChart funnelChart = new SfFunnelChart()
{
    ItemsSource = viewModel.Data,
    XBindingPath = "XValue",
    YBindingPath = "YValue"
};

funnelChart.Legend = new ChartLegend()
{
    ToggleSeriesVisibility = true // Enable the toggle visibility of the series using legend.
};

this.Content = chart;

Legend maximum size request

To set the maximum size request for the legend view, override the GetMaximumSizeCoefficient protected method in ChartLegend class. The value should be between 0 and 1, representing the maximum size request, not the desired size for the legend items layout.

<chart:SfFunnelChart>
    . . .
    <chart:SfFunnelChart.Legend>
        <chart:LegendExt/>
    </chart:SfFunnelChart.Legend>
    . . .
</chart:SfFunnelChart>
public class LegendExt : ChartLegend
{
    // Set the maximum size request for the legend view.
    protected override double GetMaximumSizeCoefficient()
    {
        return 0.7;
    }
}

SfFunnelChart chart = new SfFunnelChart();
chart.Legend = new LegendExt(); // Set the custom legend for the chart.
this.Content = chart;

Items layout

The ItemsLayout property is used to customize the arrangement and position of each legend item. The default value is null. This property accepts any layout type.

<chart:SfFunnelChart ItemsSource="{Binding Data}" 
                     XBindingPath="XValue"  
                     YBindingPath="YValue">
    <chart:SfFunnelChart.Legend>
        <chart:ChartLegend>
            <chart:ChartLegend.ItemsLayout>
                <FlexLayout Wrap="Wrap"
                            WidthRequest="400">
                </FlexLayout>
            </chart:ChartLegend.ItemsLayout>
        </chart:ChartLegend>
    </chart:SfFunnelChart.Legend>
</chart:SfFunnelChart>
SfFunnelChart chart = new SfFunnelChart()
{
    XBindingPath = "XValue",
    YBindingPath = "YValue",
    ItemsSource = new AdmissionViewModel().Data,
    LegendIcon = ChartLegendIconType.Diamond,
};
. . .
ChartLegend legend = new ChartLegend(); // Initialize the legend.

// Define the layout for legend items.
legend.ItemsLayout = new FlexLayout()
{
    Wrap = FlexWrap.Wrap,
    WidthRequest = 400
};

chart.Legend = legend; // Set the legend for the chart.
this.Content = chart;

Item template

The ChartLegend supports customizing the appearance of legend items using the ItemTemplate property. The default value of ItemsTemplate is null.

NOTE

The BindingContext of the template is the corresponding underlying legend item provided in the ChartLegendItem class.

<chart:SfFunnelChart ItemsSource="{Binding Data}" 
                     XBindingPath="XValue"  
                     YBindingPath="YValue" x:Name="chart">
    <chart:SfFunnelChart.Resources>
        <DataTemplate x:Key="legendTemplate">
            <StackLayout Orientation="Horizontal">
                <Rectangle HeightRequest="12" 
                           WidthRequest="12" Margin="3"
                           Background="{Binding IconBrush}"/>
                <Label Text="{Binding XValue}" 
                       Margin="3"/>
            </StackLayout>
        </DataTemplate>
    </chart:SfFunnelChart.Resources>  
    
    <chart:SfFunnelChart.Legend>
        <chart:ChartLegend ItemTemplate="{StaticResource legendTemplate}"/>
    </chart:SfFunnelChart.Legend>
</chart:SfFunnelChart>
SfFunnelChart chart = new SfFunnelChart()
{
    XBindingPath = "XValue",
    YBindingPath = "YValue",
    ItemsSource = new AdmissionViewModel().Data,
};
     
ChartLegend legend = new ChartLegend(); // Initialize the legend.
legend.ItemTemplate = chart.Resources["legendTemplate"] as DataTemplate; // Set the item template for the legend.
...
chart.Legend = legend; // Set the legend for the chart.
this.Content = chart;

Legend layout for funnel chart

Event

LegendItemCreated

The LegendItemCreated event is triggered when the chart legend item is created. The argument contains the LegendItem object. The following properties are present in LegendItem.

  • Text – used to get or set the text of the label.
  • TextColor – used to get or set the color of the label.
  • FontFamily - used to get or set the font family for the legend label.
  • FontAttributes - used to get or set the font style for the legend label.
  • FontSize - used to get or set the font size for the legend label.
  • TextMargin - used to get or set the margin size of labels.
  • IconBrush - used to change the color of the legend icon.
  • IconType - used to get or set the icon type for the legend icon.
  • IconHeight - used to get or set the icon height of the legend icon.
  • IconWidth - used to get or set the icon width of the legend icon.
  • IsToggled - used to get or set the toggle visibility of the legend.
  • DisableBrush - used to get or set the color of the legend when toggled.
  • Index - used to get index position of the legend.
  • Item - used to get the corresponding data points for the legend item.

    Limitations

  • Do not add items explicitly.
  • When using BindableLayouts, do not bind ItemsSource explicitly.
  • For better UX, arrange items vertically for left and right dock positions, and horizontally for top and bottom dock positions.
  • If the layout’s measured size is larger than the MaximumHeightRequest, scrolling will be enabled.
  • If MaximumHeightRequest is set to 1 and the chart’s available size is smaller than the layout’s measured size, the series may not have enough space to draw properly.