How can I have text in a Pie Chart Legend but a value in the point label?

[Nic Adams]

I am trying to create a pie chart where my series contains 4 items.

I would like the legend to display the item text

I would like the point labels to show the value for each segment.

How can I achieve this?

Thanks

Nic

[Anandaraj T]

Hi Nic, 

Thanks for using Syncfusion products. 

We have prepared a simple sample based on your requirements and it can be downloaded from the following link 

https://www.syncfusion.com/downloads/support/forum/136900/ze/PieChartLegend-357211638 

Query #1: I would like the legend to display the item text 

We can use the Text property of ChartLegendItem to customize the text displayed in a legend item. 

Please refer the following code snippet to achieve this 

[C#] 

 

            //Replace the text with custom string values of all legend items in pie chart 

            foreach (ChartLegendItem item in this.chartControl1.Legend.Items) 

            { 

                //LegendItem.Children is not null only for pie series or accumulation type series 

                int pointIndex = series.LegendItem.Children.IndexOf(item); 

 

                if (pointIndex != -1) 

                { 

                    //Customize the text displayed in legend item 

                    //You can use any string as value 

                    item.Text = series.Points[pointIndex].Category; 

                } 

                else //This is the case for first point in chart series 

                    item.Text = series.Points[0].Category; 

 

                //Customizing the text color of legend item 

                item.TextColor = Color.Black; 

            } 

 

Query #2: I would like the point labels to show the value for each segment 

We can use the Style.DisplayText property of ChartSeries to show or hide the data labels for points in a series. 

Please refer the following code snippet to achieve this 

[C#] 

 

            //Display label for points 

            series.Style.DisplayText = true; 

 

[Pie chart with different text in legend item and data labels] 

 

 

Please let us know if you have any concern. 

Regards, 

Anand

[Nic Adams]

Thanks Anad,

I think I was misled by the fact that adding a data point with a text category causes an exception if you are using BeginUpdate(). I,e if I modify your sample:

            this.chartControl1.BeginUpdate();
            this.chartControl1.Text = "Car Sales in January";
            this.chartControl1.Series.Clear();
            ChartSeries series = new ChartSeries("Car Sales", ChartSeriesType.Pie);
            series.Points.Add("SUV's", 20);
            series.Points.Add("Van", 10);
            series.Points.Add("Minivan", 30);
            series.Points.Add("Sports", 5);
            series.Points.Add("Compact", 30);

            this.chartControl1.Series.Add(series);

                        

            this.chartControl1.EndUpdate();

You will get an exception:

System.NullReferenceException

  HResult=0x80004003

  Message=Object reference not set to an instance of an object.

  Source=Syncfusion.Chart.Base

  StackTrace:

   at Syncfusion.Windows.Forms.Chart.ChartSeriesRenderer.PrepearePoints()

   at Syncfusion.Windows.Forms.Chart.ChartSeriesRenderer.CanRender()

   at Syncfusion.Windows.Forms.Chart.ChartPlace.CalculateSpace(ChartSeriesCollection series, Boolean doManyAreas, IChartAreaHost chart)

   at Syncfusion.Windows.Forms.Chart.ChartSeriesCollection.DrawSeries(Graphics g, IChartAreaHost chart)

   at Syncfusion.Windows.Forms.Chart.ChartArea.Draw2D(PaintEventArgs e, ChartPaintFlags flags)

   at Syncfusion.Windows.Forms.Chart.ChartArea.Draw(PaintEventArgs e, ChartPaintFlags flags)

   at Syncfusion.Windows.Forms.Chart.ChartControl._Paint(Graphics g, Rectangle r)

   at Syncfusion.Windows.Forms.Chart.ChartControl.OnPaint(PaintEventArgs e)

   at System.Windows.Forms.Control.PaintWithErrorHandling(PaintEventArgs e, Int16 layer)

   at System.Windows.Forms.Control.WmPaint(Message& m)

   at System.Windows.Forms.Control.WndProc(Message& m)

   at Syncfusion.Windows.Forms.Chart.ChartControl.WndProc(Message& m)

   at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

[Anandaraj T]

Hi Nic, 

Thanks for the update. 

We have confirmed that the reported issue is a defect and logged a defect report. This issue will be fixed in our upcoming service pack release which is expected to be available by the end of April 2018. 

As a workaround solution, we can use the XAxis property of ChartSeries to avoid this issue. The modified sample can be downloaded from the following link 

https://www.syncfusion.com/downloads/support/forum/136900/ze/PieChartLegend_modified-855243839 

Please refer the following code snippet to achieve this 

[C#] 

 

            //Setting X-axis for chart series 

            series.XAxis = this.chartControl1.PrimaryXAxis; 

 

Please let us know if you have any concern. 

Regards, 

Anand