Hi jwilliamsdeve...,

Use closedXML library.

For more details refer below article.

Export GridView Data to Excel using OpenXml in ASP.Net

HTML

<asp:GridView ID="GridView1" HeaderStyle-BackColor="#3AC0F2" HeaderStyle-ForeColor="White"
    RowStyle-BackColor="#A1DCF2" AlternatingRowStyle-BackColor="White" AlternatingRowStyle-ForeColor="#000"
    runat="server" AutoGenerateColumns="false" AllowPaging="true" OnPageIndexChanging="OnPageIndexChanging">
    <Columns>
        <asp:BoundField DataField="ContactName" HeaderText="Contact Name" ItemStyle-Width="150px" />
        <asp:TemplateField HeaderText="City">
            <ItemTemplate>
                <asp:HyperLink ID="lnkCity" runat="server" NavigateUrl="#" Text='<%# Eval("City") %>'></asp:HyperLink>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="Country">
            <ItemTemplate>
                <asp:TextBox ID="txtCountry" runat="server" Text='<%# Eval("Country") %>'></asp:TextBox>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="Country1">
            <ItemTemplate>
                <asp:CheckBox ID="CheckBox1" runat="server" Text = "CheckBox Control" />
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="Country2">
            <ItemTemplate>
                <asp:RadioButton ID="RadioButton1" runat="server" Text = "RadioButton Control" />
            </ItemTemplate>
        </asp:TemplateField>
    </Columns>
</asp:GridView>
<br />
<asp:Button ID="btnExport" runat="server" Text="Export To Excel" OnClick="ExportToExcel" />

Namespaces

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

Code

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        this.BindGrid();
    }
}

private void BindGrid()
{
    string strConnString = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    using (SqlConnection con = new SqlConnection(strConnString))
    {
        using (SqlCommand cmd = new SqlCommand("SELECT * FROM Customers"))
        {
            using (SqlDataAdapter sda = new SqlDataAdapter())
            {
                cmd.Connection = con;
                sda.SelectCommand = cmd;
                using (DataTable dt = new DataTable())
                {
                    sda.Fill(dt);
                    GridView1.DataSource = dt;
                    GridView1.DataBind();
                }
            }
        }
    }
}

protected void OnPageIndexChanging(object sender, GridViewPageEventArgs e)
{
    GridView1.PageIndex = e.NewPageIndex;
    this.BindGrid();
}

protected void ExportToExcel(object sender, EventArgs e)
{
    GridView1.AllowPaging = false;
    this.BindGrid();

    DataTable dt = new DataTable("GridView");
    foreach (TableCell cell in GridView1.HeaderRow.Cells)
    {
        dt.Columns.Add(cell.Text);
    }
    foreach (GridViewRow row in GridView1.Rows)
    {
        dt.Rows.Add();
        int i = 0;
        foreach (TableCell cell in row.Cells)
        {
            List<Control> controls = new List<Control>();

            if (cell.Controls.Count == 0)
            {
                dt.Rows[dt.Rows.Count - 1][i] = row.Cells[i].Text;
            }

            foreach (Control control in cell.Controls)
            {
                controls.Add(control);
            }

            foreach (Control control in controls)
            {
                switch (control.GetType().Name)
                {
                    case "HyperLink":
                        dt.Rows[dt.Rows.Count - 1][i] = (control as HyperLink).Text;
                        break;
                    case "TextBox":
                        dt.Rows[dt.Rows.Count - 1][i] = (control as TextBox).Text;
                        break;
                    case "LinkButton":
                        dt.Rows[dt.Rows.Count - 1][i] = (control as LinkButton).Text;
                        break;
                    case "CheckBox":
                        dt.Rows[dt.Rows.Count - 1][i] = (control as CheckBox).Text;
                        break;
                    case "RadioButton":
                        dt.Rows[dt.Rows.Count - 1][i] = (control as RadioButton).Text;
                        break;
                }
                cell.Controls.Remove(control);
            }
            i++;
        }
    }
    using (XLWorkbook wb = new XLWorkbook())
    {
        wb.Worksheets.Add(dt);

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

Screenshot