Gridview Add Row

 public void newrow()
    {
        DataTable dt = new DataTable();
        DataRow dr = null;
        dt.Columns.Add(new DataColumn("Select", typeof(string)));
        dt.Columns.Add(new DataColumn("sr_no", typeof(string)));
        dt.Columns.Add(new DataColumn("Source", typeof(string)));
        dt.Columns.Add(new DataColumn("Destination", typeof(string)));
        dt.Columns.Add(new DataColumn("Rate", typeof(string)));

        dr = dt.NewRow();
        dr["Select"] = string.Empty;
        dr["sr_no"] = string.Empty;
        dr["Source"] = string.Empty;
        dr["Destination"] = string.Empty;
        dr["Rate"] = string.Empty;

        dt.Rows.Add(dr);
        gridNEW_REC.DataSource = dt;
        gridNEW_REC.DataBind();



    }
    public void addnewrow()
    {

        conn.cn.Open();
        DataTable dt = new DataTable();
        DataRow dr;
        dt.Columns.Add(new DataColumn("Select", typeof(string)));
        dt.Columns.Add(new DataColumn("sr_no", typeof(string)));
        dt.Columns.Add(new DataColumn("Source", typeof(string)));
        dt.Columns.Add(new DataColumn("Destination", typeof(string)));
        dt.Columns.Add(new DataColumn("Rate", typeof(string)));
        if (gridNEW_REC.Rows.Count > 0)
        {
            for (int i = 0; i < gridNEW_REC.Rows.Count; i++)
            {
                dr = dt.NewRow();

                TextBox t1 = (TextBox)gridNEW_REC.Rows[i].Cells[1].FindControl("txtno");
                dr[1] = Convert.ToString(t1.Text);
                TextBox t2 = (TextBox)gridNEW_REC.Rows[i].Cells[2].FindControl("txtSOURCE_STATION");
                dr[2] = Convert.ToString(t2.Text);
                TextBox t3 = (TextBox)gridNEW_REC.Rows[i].Cells[4].FindControl("txtDEST_STATION");
                dr[3] = Convert.ToString(t3.Text);
                TextBox t4 = (TextBox)gridNEW_REC.Rows[i].Cells[6].FindControl("txtRATE");
                dr[4] = Convert.ToString(t4.Text);
                dt.Rows.Add(dr);
            }
            dr = dt.NewRow();
            dt.Rows.Add(dr);
            gridNEW_REC.DataSource = dt;
            gridNEW_REC.DataBind();
            auto_gen_grid_no();
        }


    }