Data Labels in ASP.NET CORE Chart

12 May 202224 minutes to read

Data label can be added to a chart series by enabling the visible option in the dataLabel. By default, the labels will arrange smartly without overlapping.

<ejs-chart id="container" width="60%">
        <e-chart-primaryxaxis valueType="Category"></e-chart-primaryxaxis>
        <e-series-collection>
            <e-series dataSource="ViewBag.dataSource" xName="x" yName="y"
                      type="@Syncfusion.EJ2.Charts.ChartSeriesType.Column">
             <e-series-marker>
                 <e-series-datalabel visible="true"></e-series-datalabel>
             </e-series-marker>
            </e-series>
        </e-series-collection>
    </ejs-chart>
public ActionResult Index()
        {
            List<Data> chartData = new List<Data>
            {
           new Data{ x= "Jan", y= 3,   fill= "#498fff", text= "January" },
           new Data{ x= "Feb", y= 3.5, fill= "#ffa060", text= "February" },
           new Data{ x= "Mar", y= 7,   fill= "#ff68b6", text= "March" },
           new Data{ x= "Apr", y= 13.5,fill= "#81e2a1", text= "April" }
            };
            ViewBag.dataSource = chartData;
            return View();
        }
        public class Data
        {
            public string x;
            public double y;
            public string fill;
            public string text;
        }

Position

Using position property, you can place the label either on Top, Middle, Bottom or Outer (outer is applicable for column and bar type series).

<ejs-chart id="container" width="60%">
        <e-chart-primaryxaxis valueType="Category"></e-chart-primaryxaxis>
        <e-series-collection>
            <e-series dataSource="ViewBag.dataSource" xName="x" yName="y"
                      type="@Syncfusion.EJ2.Charts.ChartSeriesType.Column">
             <e-series-marker>
                 <e-series-datalabel visible="true" position="Middle"></e-series-datalabel>
             </e-series-marker>
            </e-series>
        </e-series-collection>
    </ejs-chart>
public ActionResult Index()
        {
            List<Data> chartData = new List<Data>
            {
           new Data{ x= "Jan", y= 3,   fill= "#498fff", text= "January" },
           new Data{ x= "Feb", y= 3.5, fill= "#ffa060", text= "February" },
           new Data{ x= "Mar", y= 7,   fill= "#ff68b6", text= "March" },
           new Data{ x= "Apr", y= 13.5,fill= "#81e2a1", text= "April" }
            };
            ViewBag.dataSource = chartData;
            return View();
        }
        public class Data
        {
            public string x;
            public double y;
            public string fill;
            public string text;
        }

The position Outer is applicable for column and bar type series.

Datalabel template

Label content can be formatted by using the template option. Inside the template, you can add the placeholder text ${point.x} and ${point.y} to display corresponding data points x & y value. Using template property, you can set data label template in chart.

<ejs-chart id="container" width="60%">
        <e-chart-primaryxaxis valueType="Category"></e-chart-primaryxaxis>
        <e-series-collection>
            <e-series dataSource="ViewBag.dataSource" xName="x" yName="y"
                      type="@Syncfusion.EJ2.Charts.ChartSeriesType.Column">
             <e-series-marker>
                 <e-series-datalabel visible="true" position="Middle"
                  template="#template"></e-series-datalabel>
             </e-series-marker>
            </e-series>
        </e-series-collection>
    </ejs-chart>
<script id="template">
    <div style="background:#f5f5f5; border: 1px solid black; padding: 3px 3px 3px 3px">
        <div>${point.x}</div>
        <div>${point.y}</div>
    </div>
</script>
public ActionResult Index()
        {
            List<Data> chartData = new List<Data>
            {
           new Data{ x= "Jan", y= 3,   fill= "#498fff", text= "January" },
           new Data{ x= "Feb", y= 3.5, fill= "#ffa060", text= "February" },
           new Data{ x= "Mar", y= 7,   fill= "#ff68b6", text= "March" },
           new Data{ x= "Apr", y= 13.5,fill= "#81e2a1", text= "April" }
            };
            ViewBag.dataSource = chartData;
            return View();
        }
        public class Data
        {
            public string x;
            public double y;
            public string fill;
            public string text;
        }

Text Mapping

Text from the data source can be mapped using name property.

<ejs-chart id="container" width="60%">
        <e-chart-primaryxaxis valueType="Category"></e-chart-primaryxaxis>
        <e-series-collection>
            <e-series dataSource="ViewBag.dataSource" xName="x" yName="y"
                      type="@Syncfusion.EJ2.Charts.ChartSeriesType.Column">
             <e-series-marker>
                 <e-series-datalabel visible="true" name="text"></e-series-datalabel>
             </e-series-marker>
            </e-series>
        </e-series-collection>
    </ejs-chart>
public ActionResult Index()
        {
            List<Data> chartData = new List<Data>
            {
           new Data{ x= "Jan", y= 3,   fill= "#498fff", text= "January" },
           new Data{ x= "Feb", y= 3.5, fill= "#ffa060", text= "February" },
           new Data{ x= "Mar", y= 7,   fill= "#ff68b6", text= "March" },
           new Data{ x= "Apr", y= 13.5,fill= "#81e2a1", text= "April" }
            };
            ViewBag.dataSource = chartData;
            return View();
        }
        public class Data
        {
            public string x;
            public double y;
            public string fill;
            public string text;
        }

Margin

The margin for data label can be applied to use left, right, bottom and top properties.

@{
    var border = new { width = 2, color = "red" };
    var margin = new { left = 15, right = 15, bottom = 15, top = 15 };
 }
 <ejs-chart id="container" width="60%">
        <e-chart-primaryxaxis valueType="Category"></e-chart-primaryxaxis>
        <e-series-collection>
            <e-series dataSource="ViewBag.dataSource" xName="x" yName="y"
                      type="@Syncfusion.EJ2.Charts.ChartSeriesType.Column">
             <e-series-marker>
                 <e-series-datalabel visible="true" name="text" border="border" margin="margin"></e-series-datalabel>
             </e-series-marker>
            </e-series>
        </e-series-collection>
    </ejs-chart>
public ActionResult Index()
        {
            List<Data> chartData = new List<Data>
            {
           new Data{ x= "Jan", y= 3,   fill= "#498fff", text= "January" },
           new Data{ x= "Feb", y= 3.5, fill= "#ffa060", text= "February" },
           new Data{ x= "Mar", y= 7,   fill= "#ff68b6", text= "March" },
           new Data{ x= "Apr", y= 13.5,fill= "#81e2a1", text= "April" }
            };
            ViewBag.dataSource = chartData;
            return View();
        }
        public class Data
        {
            public string x;
            public double y;
            public string fill;
            public string text;
        }

Customization

The stroke and border of data label can be customized using fill and border properties. Rounded corners can be customized using rx and ry properties.

@{
    var border = new { width = 2, color = "red" };
 }
 <ejs-chart id="container" width="60%">
        <e-chart-primaryxaxis valueType="Category"></e-chart-primaryxaxis>
        <e-series-collection>
            <e-series dataSource="ViewBag.dataSource" xName="x" yName="y"
                      type="@Syncfusion.EJ2.Charts.ChartSeriesType.Column">
             <e-series-marker>
                 <e-series-datalabel visible="true" name="text" border="border" rx="10" ry="10"></e-series-datalabel>
             </e-series-marker>
            </e-series>
        </e-series-collection>
    </ejs-chart>
public ActionResult Index()
        {
            List<Data> chartData = new List<Data>
            {
           new Data{ x= "Jan", y= 3,   fill= "#498fff", text= "January" },
           new Data{ x= "Feb", y= 3.5, fill= "#ffa060", text= "February" },
           new Data{ x= "Mar", y= 7,   fill= "#ff68b6", text= "March" },
           new Data{ x= "Apr", y= 13.5,fill= "#81e2a1", text= "April" }
            };
            ViewBag.dataSource = chartData;
            return View();
        }
        public class Data
        {
            public string x;
            public double y;
            public string fill;
            public string text;
        }

rx and ry properties requires border values not to be null.

Customizing Specific Point

You can also customize the specific marker and label using pointRender and textRender event. The pointRender event allows to change the shape, color and border for a point, whereas the textRender event allows to change the text for the point.

<ejs-chart id="container" width="60%" pointRender="pointRender" textRender="textRender">
        <e-chart-primaryxaxis valueType="Category"></e-chart-primaryxaxis>
        <e-series-collection>
            <e-series dataSource="ViewBag.dataSource" xName="x" yName="y"
                      type="@Syncfusion.EJ2.Charts.ChartSeriesType.Column">
             <e-series-marker>
                 <e-series-datalabel visible="true"></e-series-datalabel>
             </e-series-marker>
            </e-series>
        </e-series-collection>
    </ejs-chart>
<script>
    pointRender=function(args) {
        if (args.point.index === 2) {
            args.fill = 'red'
        }
    },
    textRender = function (args) {
            if (args.point.index === 2) {
                args.text = 'Maximum Temperature';
                args.color = 'red';
            }
            else {
                args.cancel = true;
            }
        }
</script>
public ActionResult Index()
        {
            List<Data> chartData = new List<Data>
            {
           new Data{ x= "Jan", y= 3,   fill= "#498fff", text= "January" },
           new Data{ x= "Feb", y= 3.5, fill= "#ffa060", text= "February" },
           new Data{ x= "Mar", y= 7,   fill= "#ff68b6", text= "March" },
           new Data{ x= "Apr", y= 13.5,fill= "#81e2a1", text= "April" }
            };
            ViewBag.dataSource = chartData;
            return View();
        }
        public class Data
        {
            public string x;
            public double y;
            public string fill;
            public string text;
        }

Show percentage based on each series points

You can calculate the percentage value based on the sum for each series using the seriesRender and textRender events in the chart. In seriesRender calculate the sum of each series y values and In textRender calculate percentage value based on the sum value and modify the text.

<div class="control-section">
    <div id="container" align='center'>
        <ejs-chart id="lineContainer" textRender="onTextRender" seriesRender="onSeriesRender" title="Olympic Medal Counts - RIO">
            <e-chart-tooltipsettings enable="true">
            </e-chart-tooltipsettings>
            <e-chart-primaryxaxis valueType="Category" interval=1>
                <e-majorgridlines width="0"></e-majorgridlines>
            </e-chart-primaryxaxis>
            <e-chart-primaryyaxis>
                <e-majorgridlines width="0"></e-majorgridlines>
                <e-majorticklines width="0"></e-majorticklines>
                <e-linestyle width="0"></e-linestyle>
                <e-labelstyle color="transparent"></e-labelstyle>
            </e-chart-primaryyaxis>
            <e-chart-chartarea>
                <e-chartarea-border width="0"></e-chartarea-border>
            </e-chart-chartarea>
            <e-series-collection>
                <e-series dataSource="ViewBag.dataSource1" xName='x' yName='y' name='Gold' width=2 type="@Syncfusion.EJ2.Charts.ChartSeriesType.Column">
                    <e-series-marker>
                        <e-series-datalabel visible="true" position="Top">
                            <e-font color="#ffffff" fontWeight="600"></e-font>
                        </e-series-datalabel>
                    </e-series-marker>
                </e-series>
                <e-series dataSource="ViewBag.dataSource2" xName='x' yName='y' name='Silver' width=2 type="@Syncfusion.EJ2.Charts.ChartSeriesType.Column">
                    <e-series-marker>
                        <e-series-datalabel visible="true" position="Top">
                            <e-font fontWeight="600" color="#ffffff"></e-font>
                        </e-series-datalabel>
                    </e-series-marker>
                </e-series>
                <e-series dataSource="ViewBag.dataSource3" xName='x' yName='y' name='Bronze' width=2 type="@Syncfusion.EJ2.Charts.ChartSeriesType.Column">
                    <e-series-marker>
                        <e-series-datalabel visible="true" position="Top">
                            <e-font fontWeight="600" color="#ffffff"></e-font>
                        </e-series-datalabel>
                    </e-series-marker>
                </e-series>
            </e-series-collection>
        </ejs-chart>
    </div>
</div>


<script>
    var total = [];

    function onSeriesRender(args) {
        for (var i = 0; i < args.data.length; i++) {
            if (!total[args.data[i].x]) total[args.data[i].x] = 0;
            total[args.data[i].x] = total[args.data[i].x] + parseInt(args.data[i].y);
        }
    }
    function onTextRender(args) {
        var percentage = (parseInt(args.text) / total[args.point.x]) * 100;
        percentage = percentage % 1 === 0 ? percentage : percentage.toFixed(2);
        args.text = percentage + "%";
    }

</script>
public ActionResult Index()
        {
            List<ColumnChartData> chartData1 = new List<ColumnChartData>
            {
                new ColumnChartData { x= "USA", y = 46 },
                new ColumnChartData { x= "GBR", y = 27 },
                new ColumnChartData { x= "CHN", y = 26 }
            };
            ViewBag.dataSource1 = chartData1;

            List<ColumnChartData> chartData2 = new List<ColumnChartData>
            {
                new ColumnChartData { x= "USA", y = 37 },
                new ColumnChartData { x= "GBR", y = 23 },
                new ColumnChartData { x= "CHN", y = 18 }
            };
            ViewBag.dataSource2 = chartData2;

            List<ColumnChartData> chartData3 = new List<ColumnChartData>
            {
                new ColumnChartData { x= "USA", y = 38 },
                new ColumnChartData { x= "GBR", y = 17 },
                new ColumnChartData { x= "CHN", y = 26 }
            };
            ViewBag.dataSource3 = chartData3;
            return View();
        }
    public class ColumnChartData
        {
            public string x;
            public double y;
        }