Finding DropDownList in DetailView

protected void Page_Load(object sender, EventArgs e)     {   // Some code to bind the Details view.         if (!IsPostBack) {             DropDownList ddl = (DropDownList)this.DetailsView1.FindControl("DropDownList1");             ddl.DataSource = DataSet1; // DataSet1 returns a company List.             ddl.DataTextField = "CompanyName";             ddl.DataValueField = "CompanyID";             ddl.DataBind();         }     }     protected void SelectIndexChanged(object sender, EventArgs e)     {         DropDownList ddls = (DropDownList)this.DetailsView1.FindControl("DropDownList1");         this.TextBox1.Text = ddls.SelectedValue;     } //Codes on aspx page. <asp:DetailsView ID="DetailsView1" runat="server">             <Fields>                         <asp:TemplateField>                                 <ItemTemplate>                                     <asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="true" OnSelectedIndexChanged="SelectIndexChanged">                                     </asp:DropDownList>                                 </ItemTemplate>                         </asp:TemplateField>             </Fields> </asp:DetailsView>