Hi kate,

Please refer below sample.

HTML

<asp:HiddenField ID="hfImageData" runat="server" />
<table border="0" cellpadding="0" cellspacing="0">
    <tr>
        <td>Country:
        <asp:DropDownList ID="ddlCountries" runat="server">
            <asp:ListItem Text="USA" Value="USA" />
            <asp:ListItem Text="Germany" Value="Germany" />
            <asp:ListItem Text="France" Value="France" />
            <asp:ListItem Text="Brazil" Value="Brazil" />
        </asp:DropDownList>
            <asp:RadioButtonList ID="rblChartType" runat="server" RepeatDirection="Horizontal">
                <asp:ListItem Text="Pie" Value="1" Selected="True" />
                <asp:ListItem Text="Doughnut" Value="2" />
            </asp:RadioButtonList>
        </td>
    </tr>
</table>
<div id="dvTable" style="background-color: White; padding: 5px; width: 50%;">
    <asp:GridView ID="gvOrders" runat="server" AutoGenerateColumns="false">
        <Columns>
            <asp:BoundField DataField="OrderID" HeaderText="OrderID" />
            <asp:BoundField DataField="ShipCity" HeaderText="ShipCity" />
            <asp:BoundField DataField="ShipCountry" HeaderText="ShipCountry" />
        </Columns>
    </asp:GridView>
    <hr />
    <table border="0" cellpadding="0" cellspacing="0">
        <tr>
            <td>
                <div id="dvChart">
                </div>
            </td>
            <td>
                <div id="dvLegend">
                </div>
            </td>
        </tr>
    </table>
</div>
<br />
<asp:Button ID="btnExportToExcel" Text="Export to Excel" runat="server" OnClick="OnExportToExcel" />
<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
<script src="//cdn.jsdelivr.net/excanvas/r3/excanvas.js" type="text/javascript"></script>
<script src="//cdn.jsdelivr.net/chart.js/0.2/Chart.js" type="text/javascript"></script>
<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/html2canvas/0.4.1/html2canvas.min.js"></script>
<script type="text/javascript">
    $(function () {
        LoadChart();
        $("[id*=ddlCountries]").bind("change", function () {
            LoadChart();
        });
        $("[id*=rblChartType] input").bind("click", function () {
            LoadChart();
        });
    });
    function LoadChart() {
        var chartType = parseInt($("[id*=rblChartType] input:checked").val());
        $.ajax({
            type: "POST",
            url: "Default.aspx/GetChart",
            data: "{country: '" + $("[id*=ddlCountries]").val() + "'}",
            contentType: "application/json; charset=utf-8",
            dataType: "json",
            success: function (r) {
                $("#dvChart").html("");
                $("#dvLegend").html("");
                var data = eval(r.d);
                var el = document.createElement('canvas');
                $("#dvChart")[0].appendChild(el);

                //Fix for IE 8
                if ($.browser.msie && $.browser.version == "8.0") {
                    G_vmlCanvasManager.initElement(el);
                }
                var ctx = el.getContext('2d');
                var userStrengthsChart;
                switch (chartType) {
                    case 1:
                        userStrengthsChart = new Chart(ctx).Pie(data);
                        break;
                    case 2:
                        userStrengthsChart = new Chart(ctx).Doughnut(data);
                        break;
                }
                for (var i = 0; i < data.length; i++) {
                    var div = $("<div />");
                    div.css("margin-bottom", "10px");
                    div.html("<span style ='display:inline-block;height:10px;width:10px;background-color:" + data[i].color + "'></span> " + data[i].text);
                    $("#dvLegend").append(div);
                }
                setTimeout(function () {
                    html2canvas([document.getElementById('dvTable')], {
                        onrendered: function (canvas) {
                            $("[id*=hfImageData]").val(canvas.toDataURL());
                        }
                    });
                }, 2000);
            },
            error: function (response) {
                alert(response.responseText);
            }
        });
    }
</script>

Namespaces

C#

using System.Data;
using System.Data.SqlClient;
using System.Configuration;
using System.Drawing;
using System.IO;
using System.Text;
using System.Web.Services;

VB.Net

Imports System.Data
Imports System.Data.SqlClient
Imports System.Configuration
Imports System.Drawing
Imports System.IO
Imports System.Text
Imports System.Web.Services

Code

C#

protected void Page_Load(object sender,EventArgs e)
{
    if (!this.IsPostBack)
    {
        string constring = ConfigurationManager.ConnectionStrings["ConString"].ConnectionString;
        using (SqlConnection con = new SqlConnection(constring))
        {
            using (SqlCommand cmd = new SqlCommand("Select Top 5 OrderID,ShipCity,ShipCountry From Orders", con))
            {
                con.Open();
                gvOrders.DataSource = cmd.ExecuteReader();
                gvOrders.DataBind();
                con.Close();
            }
        }
    }
}

[WebMethod]
public static string GetChart(string country)
{
    string constr = ConfigurationManager.ConnectionStrings["ConString"].ConnectionString;
    using (SqlConnection con = new SqlConnection(constr))
    {
        string query = string.Format("select shipcity, count(orderid) from orders where shipcountry = '{0}' group by shipcity", country);
        using (SqlCommand cmd = new SqlCommand())
        {
            cmd.CommandText = query;
            cmd.CommandType = CommandType.Text;
            cmd.Connection = con;
            con.Open();
            using (SqlDataReader sdr = cmd.ExecuteReader())
            {
                StringBuilder sb = new StringBuilder();
                sb.Append("[");
                while (sdr.Read())
                {
                    sb.Append("{");
                    System.Threading.Thread.Sleep(50);
                    string color = String.Format("#{0:X6}", new Random().Next(0x1000000));
                    sb.Append(string.Format("text :'{0}', value:{1}, color: '{2}'", sdr[0], sdr[1], color));
                    sb.Append("},");
                }
                sb = sb.Remove(sb.Length - 1, 1);
                sb.Append("]");
                con.Close();
                return sb.ToString();
            }
        }
    }
}
protected void OnExportToExcel(object sender, EventArgs e)
{
    string base64 = Request.Form[hfImageData.UniqueID].Split(',')[1];
    using (MemoryStream stream = new MemoryStream(Convert.FromBase64String(base64)))
    {
        System.Drawing.Image image = new Bitmap(stream);
        image.Save(Server.MapPath("~/Temp/file.png"));
        System.Web.UI.WebControls.Image img1 = new System.Web.UI.WebControls.Image();
        img1.ImageUrl = Server.MapPath("~/Temp/file.png");
        using (StringWriter sw = new StringWriter())
        {
            using (HtmlTextWriter hw = new HtmlTextWriter(sw))
            {
                System.Web.UI.WebControls.Table table = new System.Web.UI.WebControls.Table();
                TableRow row = new TableRow();
                row.Cells.Add(new TableCell());
                row.Cells[0].Controls.Add(img1);
                table.Rows.Add(row);
                table.RenderControl(hw);

                Response.Clear();
                Response.Buffer = true;
                Response.AddHeader("content-disposition", "attachment;filename=Images.xls");
                Response.Charset = "";
                Response.ContentType = "application/vnd.ms-excel";
                Response.Write(sw.ToString());
                Response.Flush();
                Response.End();
            }
        }
    }        
}

public override void VerifyRenderingInServerForm(Control control)
{

}

VB.Net

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        Dim constring As String = ConfigurationManager.ConnectionStrings("ConString").ConnectionString
        Using con As SqlConnection = New SqlConnection(constring)
            Using cmd As SqlCommand = New SqlCommand("Select Top 5 OrderID,ShipCity,ShipCountry From Orders", con)
                con.Open()
                gvOrders.DataSource = cmd.ExecuteReader()
                gvOrders.DataBind()
                con.Close()
            End Using
        End Using
    End If
End Sub

<WebMethod>
Public Shared Function GetChart(ByVal country As String) As String
    Dim constr As String = ConfigurationManager.ConnectionStrings("ConString").ConnectionString
    Using con As SqlConnection = New SqlConnection(constr)
        Dim query As String = String.Format("select shipcity, count(orderid) from orders where shipcountry = '{0}' group by shipcity", country)
        Using cmd As SqlCommand = New SqlCommand()
            cmd.CommandText = query
            cmd.CommandType = CommandType.Text
            cmd.Connection = con
            con.Open()
            Using sdr As SqlDataReader = cmd.ExecuteReader()
                Dim sb As StringBuilder = New StringBuilder()
                sb.Append("[")
                While sdr.Read()
                    sb.Append("{")
                    System.Threading.Thread.Sleep(50)
                    Dim color As String = String.Format("#{0:X6}", New Random().[Next](&H1000000))
                    sb.Append(String.Format("text :'{0}', value:{1}, color: '{2}'", sdr(0), sdr(1), color))
                    sb.Append("},")
                End While
                sb = sb.Remove(sb.Length - 1, 1)
                sb.Append("]")
                con.Close()
                Return sb.ToString()
            End Using
        End Using
    End Using
End Function

Protected Sub OnExportToExcel(ByVal sender As Object, ByVal e As EventArgs)
    Dim base64 As String = Request.Form(hfImageData.UniqueID).Split(","c)(1)
    Using stream As MemoryStream = New MemoryStream(Convert.FromBase64String(base64))
        Dim image As System.Drawing.Image = New Bitmap(stream)
        image.Save(Server.MapPath("~/Temp/file.png"))
        Dim img1 As System.Web.UI.WebControls.Image = New System.Web.UI.WebControls.Image()
        img1.ImageUrl = Server.MapPath("~/Temp/file.png")
        Using sw As StringWriter = New StringWriter()
            Using hw As HtmlTextWriter = New HtmlTextWriter(sw)
                Dim table As System.Web.UI.WebControls.Table = New System.Web.UI.WebControls.Table()
                Dim row As TableRow = New TableRow()
                row.Cells.Add(New TableCell())
                row.Cells(0).Controls.Add(img1)
                table.Rows.Add(row)
                table.RenderControl(hw)
                Response.Clear()
                Response.Buffer = True
                Response.AddHeader("content-disposition", "attachment;filename=Images.xls")
                Response.Charset = ""
                Response.ContentType = "application/vnd.ms-excel"
                Response.Write(sw.ToString())
                Response.Flush()
                Response.[End]()
            End Using
        End Using
    End Using
End Sub

Public Overrides Sub VerifyRenderingInServerForm(ByVal control As Control)
End Sub

Screenshot

Output