Simulating Content PlaceHolder without MasterPages

Posted on Sunday September 2013

Simulating Content PlaceHolder without MasterPages

Oh back in the deeply wrong world of WebForms...

So somewhere in the misty depths of an ASPX page I wish to render out all the scraps of javascript that any ASCX user controls may require. You could use the ScriptManager and RegisterClientScriptBlock (and LoadScriptsBeforeUI=false), or be very tidy and bundle and minify all the little script snippets together.

Other times it is desirable to just keep all the HTML and script together in a single ASCX.

With a master page we can use ContentPlaceHolder, but in just a normal ASPX page?

Behold. Add a placeholder to the ASPX, prehaps at the bottom of the page.

<asp:PlaceHolder runat="server" ID="ScriptsPlaceHolder"></asp:PlaceHolder>

In the user control we have a little javascript snippet, prehaps to hook up a click event. Who knows.

    html normally goes here

    <my:RenderPlaceHolder runat="server" PlaceHolderId="ScriptsPlaceHolder">
           <script type="text/javascript">
              console.log('this script is rendered from a user control 
    							into it's parents placeholder');

The RenderPlaceHolder control will look up into the page and find the corresponding PlaceHolder control, dumping it's content into it.

    using System.Web.UI;

    [ParseChildren(true, "Content")]
    public class RenderPlaceHolder : UserControl
        protected override void Render(HtmlTextWriter writer)
            // you should probably do some null reference checks here...

        public Control Content { get; set; }

        public string PlaceHolderId { get; set; }