Must declare the scalar variable "@startdate".?

Hi,

It shows the following error?Must declare the scalar variable "@startdate".

public void reportsgridview()
{
SqlConnection con = new SqlConnection("data source=mars-104;initial catalog=marsweb;integrated security=true");
SqlCommand cmd = new SqlCommand("select compname,compaddress,invoiceno,orderno,convert(varchar,ondate,105),convert(varchar,invoicedate,105),amountstatus,netamount,netvat,tamount from tbl_report2 where invoicedate between @startdate and @enddate order by invoicedate asc", con);// Here it shows the error:Must declare the scalar variable "@startdate".?
cmd.Parameters.AddWithValue("@startdate", Convert.ToDateTime(txt_startdate.Text));
cmd.Parameters.AddWithValue("@enddate", Convert.ToDateTime(txt_enddate.Text));
con.Open();

SqlDataAdapter da = new SqlDataAdapter(cmd);
DataTable dt = new DataTable();
da.Fill(dt);
if (dt.Rows.Count > 0)
{
GridView1.DataSource = dt;
}
else
{
MessageBox.Show("no record found");
}
}

Best,
Sudheep.