How to achieve the draggable legend in WPF Chart (SfChart)?

3 mins read

This article describes how to make it possible for end-users to move a chart's legend at runtime.

To change the position of legend at any arbitrary location inside the chart area, set the DockPosition as Floating with subscribing the necessary mouse events to change their X and Y legend offset as per follows.

[XAML]

<chart:SfChart x:Name="sfChart" MouseMove="SfChart_MouseMove" 
                        MouseLeftButtonUp= "SfChart_MouseLeftButtonUp">
            <chart:SfChart.Legend>
                <chart:ChartLegend  x:Name="legend" DockPosition="Floating"
                                   MouseLeftButtonDown="Legend_MouseLeftButtonDown"
                                   OffsetX="200"/>
            </chart:SfChart.Legend>
            …
</chart:SfChart>

[C#]

private bool isDragable = false;
private void SfChart_MouseMove(object sender, MouseEventArgs e)
{
     var chart = sender as SfChart;
     if (isDragable)
     {
          var position = e.GetPosition(chart);
          ChartLegend legend = chart.Legend as ChartLegend;
          legend.OffsetX = position.X - (chart.SeriesClipRect.Left + legend.DesiredSize.Width / 2);
          legend.OffsetY = position.Y - (chart.SeriesClipRect.Top + legend.DesiredSize.Height / 2);
 
          if ((chart.Legend as ChartLegend).IsMouseOver)
          {
              if (Mouse.OverrideCursor == null)
                  Mouse.OverrideCursor = Cursors.Hand;
          }
     }
}
 
private void SfChart_MouseLeftButtonUP(object sender, MouseButtonEventArgs e)
{
            isDragable = false;
}
 
private void Legend_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
            isDragable = true;
}

Output

Drag the legend in WPF Chart

Download the complete sample here.

How to achieve the draggable legend in WPF Chart (SfChart)?

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