C# How to export data direct from reportviewer to excel.

private void btnExcel_Click(object sender, EventArgs e)
{
    Warning[] warnings;
    string[] streamids;
    string mimeType;
    string encoding;
    string extension;
    byte[] bytes = reportViewer1.LocalReport.Render(
        "Excel", null, out mimeType, out encoding, out extension, out streamids, out warnings);

    SaveFileDialog save = new SaveFileDialog();
    save.Filter = "Excel File (*.xls)|*.xls|All Files (*.*)|*.*";
    save.FileName= "File Name";
    if (save.ShowDialog() == DialogResult.OK)
    {
        FileStream fs = new FileStream(save.FileName, FileMode.Create);
        fs.Write(bytes, 0, bytes.Length);
        fs.Close();

        MessageBox.Show("Saved");
    }
}