asp.net gridview row adding

DataTable dt;
    string str = ConfigurationManager.ConnectionStrings["conn"].ToString();
    protected void Page_Load(object sender, EventArgs e)
    {
        SqlConnection conn = new SqlConnection(str);
        conn.Open();
        dt = new DataTable();
        DataColumn dc = new DataColumn();
        dc = new DataColumn("Medicine");
        dt.Columns.Add(dc);
        DataRow dr = dt.NewRow();
        dr["Medicine"] = this.medicine.SelectedValue;
        dt.Rows.Add(dr);
        GridView1.DataSource = dt;
        GridView1.DataBind();
    }

<asp:DropDownList ID="medicine" runat="server" AutoPostBack="True"
            Height="22px" Width="262px">
            <asp:ListItem>agfdgd</asp:ListItem>
            <asp:ListItem>bgfdgd</asp:ListItem>
            <asp:ListItem>cgfdgd</asp:ListItem>
            <asp:ListItem>dgfdgd</asp:ListItem>
            <asp:ListItem>egfdgd</asp:ListItem>
            <asp:ListItem>fgfdgd</asp:ListItem>
            <asp:ListItem>ggfdgd</asp:ListItem>
        </asp:DropDownList>
        <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False"
            Height="59px" Width="404px">
            <Columns>
                <asp:BoundField DataField="Medicine" HeaderText="name" />
            </Columns>
        </asp:GridView>