Export filtered GridView record to Excel using C# in ASP.Net

Hi seryu,

Here i have created sample that full fill your requirement.

<div>
    <table>
        <tr>
            <td>
                City
            </td>
            <td>
                <asp:DropDownList runat="server" ID="ddlCity">
                    <asp:ListItem Text="Select" />
                    <asp:ListItem Text="Warszawa" />
                    <asp:ListItem Text="Buenos Aires" />
                    <asp:ListItem Text="London" />
                </asp:DropDownList>
            </td>
        </tr>
        <tr>
            <td>
                Country
            </td>
            <td>
                <asp:DropDownList ID="ddlCountry" runat="server">
                    <asp:ListItem Text="Select" />
                    <asp:ListItem Text="Poland" />
                    <asp:ListItem Text="Belgium" />
                    <asp:ListItem Text="Argentina" />
                    <asp:ListItem Text="UK" />
                </asp:DropDownList>
            </td>
        </tr>
        <tr>
            <td colspan="2">
                <asp:GridView runat="server" ID="gvCustomers" />
            </td>
        </tr>
        <tr>
            <td>
                <asp:Button ID="btnSearch" runat="server" Text="Search" OnClick="Search" />
            </td>
            <td>
                <asp:Button ID="btnExport" runat="server" Text="Export To Excel" OnClick="ExportExcel" />
            </td>
        </tr>
    </table>
</div>

Code

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        DataTable dt = new DataTable();
        string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
        string query = "SELECT TOP 10 ContactName,City,Country FROM Customers";
        using (SqlConnection con = new SqlConnection(constr))
        {
            using (SqlCommand cmd = new SqlCommand(query))
            {
                using (SqlDataAdapter sda = new SqlDataAdapter())
                {
                    cmd.Connection = con;
                    sda.SelectCommand = cmd;
                    sda.Fill(dt);
                    ViewState["Data"] = dt;
                    gvCustomers.DataSource = dt;
                    gvCustomers.DataBind();
                }
            }
        }
    }
}

protected void Search(object sender, EventArgs e)
{
    DataTable dt = new DataTable();
    string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    string query = "SELECT TOP 10 ContactName,City,Country FROM Customers WHERE City = @City AND Country = @Country";
    using (SqlConnection con = new SqlConnection(constr))
    {
        using (SqlCommand cmd = new SqlCommand(query))
        {
            cmd.Parameters.AddWithValue("@City", ddlCity.SelectedItem.Text.Trim());
            cmd.Parameters.AddWithValue("@Country", ddlCountry.SelectedItem.Text.Trim());
            using (SqlDataAdapter sda = new SqlDataAdapter())
            {
                cmd.Connection = con;
                sda.SelectCommand = cmd;
                sda.Fill(dt);
                ViewState["Data"] = dt;
                gvCustomers.DataSource = dt;
                gvCustomers.DataBind();
            }
        }
    }
}

protected void ExportExcel(object sender, EventArgs e)
{
    DataSet ds = new DataSet();
    ds.Tables.Add(ViewState["Data"] as DataTable);
    using (XLWorkbook wb = new XLWorkbook())
    {
        foreach (DataTable dt in ds.Tables)
        {
            //Add DataTable as Worksheet.
            wb.Worksheets.Add(dt);
        }

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

Screenshot