如何創建和填充下拉菜單編程

Question

我試圖使用一個for循環像這樣創建的下拉列表：創建

private void Page_Load(object sender, System.EventArgs e) 
    { 
     //build placeholder 
     for(int x = 0; x <= 10; x++) { 

      DropDownList dp = new DropDownList(); 
      dp.ID = "carrirerDp " + x.ToString(); 
      dp.DataSource = PhoneCarrierSqlDataSource;    
      dp.DataTextField = "carrier_name"; 
      dp.DataValueField = "crr_id"; 
      DropDownPlaceHolder.Controls.Add(dp); 
      DropDownPlaceHolder.Controls.Add(new LiteralControl("<br>")); 
     }  
    } 

的下拉菜單，但它們是空的。 Execpt我與ASP標記

<asp:DropDownList ID="PhoneCarrierDropDownList" runat="server" 
    DataSourceID="PhoneCarrierSqlDataSource" DataTextField="carrier_name" 
    DataValueField="crr_id"> 
</asp:DropDownList> 

<asp:SqlDataSource ID="PhoneCarrierSqlDataSource" runat="server" 
    ConnectionString="<%$ ConnectionStrings:ApplicationServices %>" 
    SelectCommand="SELECT * 
        FROM Table"> 
</asp:SqlDataSource> 

創建，並在這裏的人是佔位：

<asp:PlaceHolder id="Area1" runat="server"></asp:PlaceHolder> 

Answer 1

您還沒有數據綁定：

dp.DataBind();