GetElementByID 在服务器端，asp.net？

Question

I have something like that:

  <asp:ListView ID="lvList" runat="server">
    <LayoutTemplate>
      <select id="select_list">
        <option value="-1">
          select one
        </option>
        <asp:PlaceHolder ID="itemPlaceHolder" runat="server" />
      </select>
    </LayoutTemplate>
    <ItemTemplate>
      <option value="<%# Eval("code") %>">
        <%# Eval("Name") %>
      </option>
    </ItemTemplate>
  </asp:ListView>

And I want to access select_list at server side, after a button get submitted.. I tried FindControl("select_list") , lvList.FindControl("select_list") , Request.Form["select_list"] - none of them gave my the control back..

Is there some way to get the control by its id, just like JS getElementByID ?

Thanks.

Answer 1

Is this for academic purpose? You could write the same code with lesser markup using an asp:DropDownList

<asp:DropDownList ID="select_list" runat="server"
            AppendDataBoundItems="true"
            DataTextField="Name"
            DataValueField="code">
    <asp:ListItem Text="select one" Value="-1" />
</asp:DropDownList>

If you are particular about using ListView do run your HTML Control at server runat="server"

Answer 2

Is there a reason you are using a ListView to fill a HTML select rather than just using a DropDownList ?

You can just replace the entire ListView with a DropDownList like so:

<asp:DropDownList ID="SampleDdl" runat="server" AppendDataBoundItems="true">
    <asp:ListItem Text="Select one" Value="-1" />
</asp:DropDownList>

Then, in your code behind, you can just bind the DropDownList like so:

SampleDdl.DataSource = DataSet
SampleDdl.DataValueField = "Code"
SampleDdl.DataTextField = "Name"
SampleDdl.DataBind()

This will automatically populate the DropDownList for you. Specifying the DataValueField will automatically populate the Value attributes in all the options of the DropDownList . Similarly, the DataTextField will populate the Text attributes.

It's also important to note that I've added AppendDataBoundItems="true" in my sample above - you will need to add that so that the default option of "Select one" isn't replaced by the data that is bound to the control - instead the bound data is appended after the existing option.

If you use a DropDownList , you can then just access the control in your code-behind by directly referring to SampleDdl .

Answer 3

In order for a control to have a server representation of itself you have to declare it with the attribute runat="server"

Try

<asp:ListView ID="lvList" runat="server">
<LayoutTemplate>
  <select id="select_list" runat="server">
    <option value="-1">
      select one
    </option>
    <asp:PlaceHolder ID="itemPlaceHolder" runat="server" />
  </select>
</LayoutTemplate>
<ItemTemplate>
  <option value="<%# Eval("code") %>">
    <%# Eval("Name") %>
  </option>
</ItemTemplate>

and then try accessing using FindControl("select_list")

Answer 4

the control you are trying to access is client side control. If you want to access it server side try adding a tag like runat="server". Something like

<select id="..." runat="server">

Answer 5

You should set its runat attribute to "server" and use the ListView's LayoutTemplate property to obtain it.

<asp:ListView ID="lvList" runat="server">
    <LayoutTemplate>
      <select id="select_list" runat="server">
        <option value="-1">
          select one
        </option>
        <asp:PlaceHolder ID="itemPlaceHolder" runat="server" />
      </select>
    </LayoutTemplate>
    <ItemTemplate>
      <option value="<%# Eval("code") %>">
        <%# Eval("Name") %>
      </option>
    </ItemTemplate>
  </asp:ListView>