Live Chart in Blazor Charts Component

4 Aug 20217 minutes to read

Live update in a chart can be achieved using the timer to update the datasource with real-time data and refresh the chart. Follow the steps below to update a chart with real-time data.

Step 1:

Render a chart with the required series using ChartSeriesCollection.

<SfChart @ref="liveChart" Title="CPU Usage" Width="100%" >
    <ChartPrimaryXAxis ValueType="Syncfusion.Blazor.Charts.ValueType.DateTime" Title="Time (s)">
        <ChartAxisMajorGridLines Width="0"></ChartAxisMajorGridLines>
    </ChartPrimaryXAxis>
    <ChartPrimaryYAxis Title="Usage" Minimum="0" Interval="20" Maximum="100" >
        <ChartAxisLineStyle Width="0" Color="transparent"></ChartAxisLineStyle>
    </ChartPrimaryYAxis>
    <ChartSeriesCollection>
        <ChartSeries Type="ChartSeriesType.Line" Width="2" DataSource="@DataPoints"
                        XName="Time" YName="CPU_Usage">
            <ChartSeriesAnimation Enable="false"></ChartSeriesAnimation>
        </ChartSeries>
    </ChartSeriesCollection>
</SfChart>

Step 2:

Labels of the axes can be formated based on our need using the LabelFormat property of the ChartAxis. Since the chart will be updated in seconds, the LabelFormat has been set as mm:ss for the ChartPrimaryXAxis to display minutes and second in the axis labels. Similarly ChartPrimaryYAxis labels can also be formated as shown below using its LabelFormat property.

<SfChart @ref="liveChart" Title="CPU Usage" Width="100%" >
    <ChartPrimaryXAxis ValueType="Syncfusion.Blazor.Charts.ValueType.DateTime" LabelFormat="mm:ss" Title="Time (s)">
        <ChartAxisMajorGridLines Width="0"></ChartAxisMajorGridLines>
    </ChartPrimaryXAxis>
    <ChartPrimaryYAxis Title="Usage" Minimum="0" Interval="20" Maximum="100" LabelFormat="{value}%">
        <ChartAxisLineStyle Width="0" Color="transparent"></ChartAxisLineStyle>
    </ChartPrimaryYAxis>
    <ChartSeriesCollection>
        <ChartSeries Type="ChartSeriesType.Line" Width="2" DataSource="@DataPoints"
                        XName="Time" YName="CPU_Usage">
            <ChartSeriesAnimation Enable="false"></ChartSeriesAnimation>
        </ChartSeries>
    </ChartSeriesCollection>
</SfChart>

Step 3:

Add a timer to automatically update the chart every 500 milliseconds by calling the AddData function, which removes the first data from the data points collection, which is of the ObservableCollection type, and adds a new data to it. Since this ObservableCollection type is used as the data source, it is triggered whenever there is a data update within it.

protected override void OnInitialized()
{
    // Provide the chart with initial data during page load.
    DataPoints = new ObservableCollection<ChartDataPoint>();
    for (int i = 0; i < dataLength; i++)
        DataPoints.Add(new ChartDataPoint
        {
            Time = DateTime.Now.AddSeconds(i + 10),
            CPU_Usage = randomNum.Next(30, 80)
        });
    // Starting live update in the chart.
    timer = new Timer(500);
    timer.Elapsed += AddData;
    timer.AutoReset = true;
    timer.Enabled = true;
}

private void AddData(Object source, ElapsedEventArgs e)
{
    dataLength++;
    DataPoints.RemoveAt(0);
    DataPoints.Add(new ChartDataPoint
    {
        Time = DateTime.Now.AddSeconds(dataLength + 10),
        CPU_Usage = randomNum.Next(30, 80)
    });
}

The complete code snippet for the preceding steps is available below.

@using Syncfusion.Blazor.Charts
@using System.Collections.ObjectModel
@using System.Timers

<div class="control-section" align="center">
    <SfChart @ref="liveChart" Title="CPU Usage" Width="100%" >
        <ChartPrimaryXAxis ValueType="Syncfusion.Blazor.Charts.ValueType.DateTime" LabelFormat="mm:ss" Title="Time (s)">
            <ChartAxisMajorGridLines Width="0"></ChartAxisMajorGridLines>
        </ChartPrimaryXAxis>
        <ChartPrimaryYAxis Title="Usage" Minimum="0" Interval="20" Maximum="100" LabelFormat="{value}%">
            <ChartAxisLineStyle Width="0" Color="transparent"></ChartAxisLineStyle>
        </ChartPrimaryYAxis>
        <ChartSeriesCollection>
            <ChartSeries Type="ChartSeriesType.Line" Width="2" DataSource="@DataPoints"
                         XName="@nameof(ChartDataPoint.Time)" YName="@nameof(ChartDataPoint.CPU_Usage)">
                <ChartSeriesAnimation Enable="false"></ChartSeriesAnimation>
            </ChartSeries>
        </ChartSeriesCollection>
    </SfChart>
</div>

@code{

    private static Timer timer;
    private SfChart liveChart;
    private double dataLength = 100;
    private Random randomNum = new Random();
    public ObservableCollection<ChartDataPoint> DataPoints;

    protected override void OnInitialized()
    {
        // Provide the chart with initial data during page load.
        DataPoints = new ObservableCollection<ChartDataPoint>();
        for (int i = 0; i < dataLength; i++)
            DataPoints.Add(new ChartDataPoint
            {
                Time = DateTime.Now.AddSeconds(i + 10),
                CPU_Usage = randomNum.Next(30, 80)
            });
        // Starting live update in the chart.
        timer = new Timer(500);
        timer.Elapsed += AddData;
        timer.AutoReset = true;
        timer.Enabled = true;
    }

    private void AddData(Object source, ElapsedEventArgs e)
    {
        if (liveChart == null)
            return;
        dataLength++;
        DataPoints.RemoveAt(0);
        DataPoints.Add(new ChartDataPoint
        {
            Time = DateTime.Now.AddSeconds(dataLength + 10),
            CPU_Usage = randomNum.Next(30, 80)
        });
    }

    public class ChartDataPoint
    {
        public DateTime Time { get; set; }
        public double CPU_Usage { get; set; }
    }
}

Refer to our Blazor Charts feature tour page for its groundbreaking feature representations and also explore our Blazor Chart Example to know various chart types and how to represent time-dependent data, showing trends at equal intervals.