Access to div from codebehind who's outside a repeater Asp.net C#

Question

I know its maybe unusual, but i want add htmlGenericControl to a div (it's outside a repeater) in ItemDataBound from CodeBehind..

HtmlGenericControl slider = (HtmlGenericControl)e.Item.FindControl("slider");

htmlGenericControl input = new HtmlGenericControl("input");
input.Attributes.Add("type", "radio");
input.Attributes.Add("name", "slide_switch");
input.Attributes.Add("id", string.Format("projectImage-{0}", item.ProjectImageId));

slider.Controls.Add(input);

but its return null everytime. this is the aspx code:

  <div class="slider">
      <asp:Repeater ID="rptProjectImages" runat="server" OnItemDataBound="rptProjectImages_ItemDataBound">

           <ItemTemplate>
           </ItemTemplate>

       </asp:Repeater>
   </div>

Answer 1

Several issues with this code.

First, your div is client-side only, from server-side point of view it's just a string. Turn it into server-side control with:

<div class="slider" runat="server" ID="slider">

Second, FindControl looks for immediate children only, in your case children of the repeater item. slider is not one of those. Moreover, it is not a part of the repeater item template and should be accessible as in in code behind, so just

slider.Controls.Add(...

That is unless slider and the repeater you showed are a part of some other template of some "outer" control. In which case make sure to use that "outer" control to call FindControl on.

Finally, don't mess with id. I bet this is either going to be overridden by ASP.NET, or will cause issues on the page. Instead set client ID mode to static and assign ID property:

input.ClientIDMode = ClientIDMode.Static;
input.ID = string.Format("projectImage_{0}", item.ProjectImageId);

This is eventually output the same value for id you needed, but in more ASP.NET compliant way. One note though is that I replaced "-" with "_" - server side controls cannot have hyphens in ID