In this article I will explain with an example, how to create Pie Chart using ChartJS in ASP.Net with C# and VB.Net.
The HTML5 Canvas charts have been implemented using Chart.js library to which JSON object is supplied as source of data.
 
 

ChartJS plugin

Plase refer the following link for documentation for the jQuery ChartJS plugin
https://www.chartjs.org/
 
 

Database

I have made use of the following table FruitChart with the schema as follows.
Create Pie Chart using ChartJS in ASP.Net
I have already inserted few records in the table.
Create Pie Chart using ChartJS in ASP.Net
 
Note: You can download the database table SQL by clicking the download link below.
           Download SQL file
 
 

HTML Markup

The HTML Markup consists of following element:
canvas – For displaying chart.
<canvas id="dvChart"></canvas>
 
 

Generating JSON string for the Chart in C# and VB.Net

Inside the Page_Load event handler, the records are fetched from the FruitChart Table of SQL Server database using DataReader.
Then, inside the WHILE loop, a JSON string is generated with following properties:
Name – This property will be displayed in Labels.
Popularity – This property will be used to populate the Chart.
Color – This property will be used to set the color of the various sections of the Chart.
Finally, the JSON string is set into a protected property ChartData, which will be used inside then JavaScript function for populating the Chart.
C#
protected string ChartData { get; set; }
 
protected  void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
        string query = "SELECT Name, Popularity, Color FROM FruitChart";
        using (SqlConnection con = new SqlConnection(constr))
        {
            using (SqlCommand cmd = new SqlCommand(query, con))
            {
                con.Open();
                string data = "[";
                using (SqlDataReader sdr = cmd.ExecuteReader())
                {
                    while (sdr.Read())
                    {
                        data += "{";
                        data += string.Format("Name : '{0}', Popularity : {1}, Color : '{2}'", sdr["Name"], sdr["Popularity"], sdr["Color"]);
                        data += "}, ";
                    }
                    data = data.Remove(data.Length - 1, 1);
                    data += "]";
                }
                con.Close();
                this.ChartData = data;
            }
        }
    }
}
 
VB.Net
Protected Property ChartData As String
 
Protected Sub Page_Load(sender As Object, e As EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        Dim constr As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
        Dim query As String = "SELECT Name, Popularity, Color FROM FruitChart"
        Using con As SqlConnection = New SqlConnection(constr)
            Using cmd As SqlCommand = New SqlCommand(query, con)
                con.Open()
                Dim data As String = "["
                Using sdr As SqlDataReader = cmd.ExecuteReader()
                    While sdr.Read()
                        data += "{"
                        data += String.Format("Name : '{0}', Popularity : {1}, Color : '{2}'", sdr("Name"), sdr("Popularity"), sdr("Color"))
                        data += "}, "
                    End While
                    data = data.Remove(data.Length - 1, 1)
                    data += "]"
                End Using
                con.Close()
                Me.ChartData = data
            End Using
        End Using
    End If
End Sub
 
 

Populating Chart using JSON data

Implementing ChartJS plugin

Inside the HTML Markup, the following script files are inherited.
1. jquery.min.js
2. chart.umd.min.js
 
Inside the jQuery document ready event handler, the PopulateChart JavaScript function is called which accepts two parameters:
1. JSON object – The JSON string received from Server-Side (Code-Behind) is converted to JSON object.
2. Chart type – The type of chart.
 

PopulateChart JavaScript function

Inside this function, the canvas element is referenced and passed as parameter to a newly created object of Chart.js library.
Then, the following other properties are set:
type – the type of Chart.
data – here the Chart Labels, Data and Color are mapped with the JSON values.
options – here the Chart properties such has height, width, etc. and the Legend are specified.
Note: For more information, please refer the Chart.js documentation: Pie Chart documentation.
 
Finally, the legends are defined and the Chart is populated.
<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.7.1/jquery.min.js"></script>
<script type="text/javascript" src="https://cdn.jsdelivr.net/npm/chart.js@4.4.7/dist/chart.umd.min.js"></script>
<canvas id="dvChart"></canvas>
<script type="text/javascript">
    $(function () {
        PopulateChart(eval("<%=this.ChartData%>"), 'pie');
    });
 
    function PopulateChart(chartData, chartType) {
        var dvChart = $('#dvChart');
        var chart = new Chart(dvChart, {
            type: chartType,
            data: {
                labels: chartData.map(fruit => fruit.Name),
                datasets: [{
                    data: chartData.map(fruit => fruit.Popularity),
                    backgroundColor: chartData.map(fruit => fruit.Color),
                    borderColor: ['#FFF'],
                    borderWidth: 1
                }]
            },
            options: {
                plugins: {
                    legend: {
                        labels: {
                            boxWidth: 10, // Width of legend box
                            boxHeight: 10 // Height of legend box
                        },
                        display: true, // Show hide legends
                        position: 'right', //'left', 'right', 'top', 'bottom'
                        align: 'center', // 'start', 'center', 'end'
                        reverse: false // Reverse order
                    }
                }
            }
        });
    };
</script>
 
 

Screenshot

Create Pie Chart using ChartJS in ASP.Net
 
 

Demo

View Demo
 
 

Downloads

ChartJS_Download Code