Hi softly21,

Using the below article i have created the example. Refer below code.

Export data from SQL Server to Excel in ASP.Net using C# and VB.Net

HTML

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false" OnRowDataBound="OnRowDataBound">
    <Columns>
        <asp:BoundField DataField="Id" HeaderText="Id" ItemStyle-Width="30" />
        <asp:BoundField DataField="Name" HeaderText="Name" ItemStyle-Width="150" />
    </Columns>
</asp:GridView>
<br />
<asp:Button Text="Export To Excel" runat="server" OnClick="OnExportExcel" />
<style type="text/css">
    .tooltip {
        position: absolute;
        top: 0;
        left: 0;
        z-index: 3;
        display: none;
        background-color: #FB66AA;
        color: White;
        padding: 5px;
        font-size: 10pt;
        font-family: Arial;
    }

    table td {
        cursor: pointer;
    }
</style>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
<script type="text/javascript" src="http://cdn.jsdelivr.net/jquery.simpletip/1.3.1/jquery.simpletip-1.3.1.min.js"></script>
<script type="text/javascript">
    $(function () {
        $('[id*=GridView1] tr').each(function () {
            var toolTip = $(this).attr("title");
            $(this).find("td").each(function () {
                $(this).simpletip({
                    content: toolTip
                });
            });
            $(this).removeAttr("title");
        });
    });
</script>

Namespaces

C#

using System.Data;
using System.IO;
using ClosedXML.Excel;

VB.Net

Imports System.Data
Imports System.IO
Imports ClosedXML.Excel

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        GridView1.DataSource = GetData();
        GridView1.DataBind();
    }
}

private DataTable GetData()
{
    DataTable dt = new DataTable();
    dt.Columns.AddRange(new DataColumn[3] {
                    new DataColumn("Id", typeof(int)),
                    new DataColumn("Name", typeof(string)),
                    new DataColumn("Description",typeof(string)) });
    dt.Rows.Add(1, "John Hammond", "Works as a scientist in USA.");
    dt.Rows.Add(2, "Mudassar Khan", "ASP.Net programmer and consultant in India.");
    dt.Rows.Add(3, "Suzanne Mathews", "Content Writer in France.");
    dt.Rows.Add(4, "Robert Schidner", "Wild life photographer in Russia.");
    ViewState["GridData"] = dt;

    return dt;
}

protected void OnRowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        e.Row.ToolTip = (e.Row.DataItem as DataRowView)["Description"].ToString();
    }
}

protected void OnExportExcel(object sender, EventArgs e)
{
    using (DataTable dt = (DataTable)ViewState["GridData"])
    {
        // Remove column to hide in excel.
        dt.Columns.Remove("Description");
        using (XLWorkbook wb = new XLWorkbook())
        {
            wb.Worksheets.Add(dt, "Customers");

            Response.Clear();
            Response.Buffer = true;
            Response.Charset = "";
            Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
            Response.AddHeader("content-disposition", "attachment;filename=Customers.xlsx");
            using (MemoryStream MyMemoryStream = new MemoryStream())
            {
                wb.SaveAs(MyMemoryStream);
                MyMemoryStream.WriteTo(Response.OutputStream);
                Response.Flush();
                Response.End();
            }
        }
    }
}

VB.Net

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        GridView1.DataSource = GetData()
        GridView1.DataBind()
    End If
End Sub

Private Function GetData() As DataTable
    Dim dt As DataTable = New DataTable()
    dt.Columns.AddRange(New DataColumn(2) {
                            New DataColumn("Id", GetType(Integer)),
                            New DataColumn("Name", GetType(String)),
                            New DataColumn("Description", GetType(String))})
    dt.Rows.Add(1, "John Hammond", "Works as a scientist in USA.")
    dt.Rows.Add(2, "Mudassar Khan", "ASP.Net programmer and consultant in India.")
    dt.Rows.Add(3, "Suzanne Mathews", "Content Writer in France.")
    dt.Rows.Add(4, "Robert Schidner", "Wild life photographer in Russia.")
    ViewState("GridData") = dt
    Return dt
End Function

Protected Sub OnRowDataBound(ByVal sender As Object, ByVal e As GridViewRowEventArgs)
    If e.Row.RowType = DataControlRowType.DataRow Then
        e.Row.ToolTip = (TryCast(e.Row.DataItem, DataRowView))("Description").ToString()
    End If
End Sub

Protected Sub OnExportExcel(ByVal sender As Object, ByVal e As EventArgs)
    Using dt As DataTable = CType(ViewState("GridData"), DataTable)
        ' Remove column to hide in excel.
        dt.Columns.Remove("Description")

        Using wb As XLWorkbook = New XLWorkbook()
            wb.Worksheets.Add(dt, "Customers")
            Response.Clear()
            Response.Buffer = True
            Response.Charset = ""
            Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
            Response.AddHeader("content-disposition", "attachment;filename=Customers.xlsx")

            Using MyMemoryStream As MemoryStream = New MemoryStream()
                wb.SaveAs(MyMemoryStream)
                MyMemoryStream.WriteTo(Response.OutputStream)
                Response.Flush()
                Response.End()
            End Using
        End Using
    End Using
End Sub

Screenshot