Remove statically added controls at runtime

The Scenario: I have an asp.net website where I show a div popup on page load for taking a few user details. When a user inputs the details, or closes the popup, I set up a flag cookie so that the popup is not displayed again for the user. The div is in the MasterPage so that it is displayed no matter on which page a user lands first time. The div contains an UpdatePanel which has all the controls required for taking the details. This whole functionality is working fine.

The Problem: Now this div popup is not showing(by setting display:none) on subsequent postbacks(which I want), but the html markup is still loading with the page unnecessarily adding to the page size. What I would idealy want to do is: Check if flag cookie is set. If no, show the popup, else remove the popup's markup from the page.

Now since the div is not a server control, I cannot possibly remove it and the all the controls inside it. So, I thought of removing the UpdatePanel from the page:

protect开发者_运维百科ed void Page_Load(object sender, EventArgs e)
    {
        if (Request.Cookies["flag"] != null)
        {
            if (Page.Controls.Contains(updpnl_contact))
            {
                Page.Controls.Remove(updpnl_contact);
                updpnl_contact.Dispose();
            }
        }
    }

But I guess this tends to work with dynamically added controls only, and since the control is added at Design Time, it is not being removed.

Is there any way I can achieve this?

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If you add a runat="server" attribute to your <div> element, it will be available in the code-behind. You'll need an id on it as well. Then you can just toggle the Visible property. If this property is false, the control won't be rendered to the client (i.e. no HTML markup).

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What you're trying to do is not at all the usual workflow. I tend to think that it will not work as it would mess up control tree, maybe even corrupt the viewstate and so on.

As a possible solution, you can put it's visibility to hidden in the code behind. This, in the contrary to the usual 'gut feeling', doesn't work like the css propery 'display:none' for example - instead the control will not even be rendered into the page when it's not visible. This may be the workaround for you.

Happy coding.

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A more efficient approach would be to create the panel as a UserControl and load it dynamically in codebehind when it's needed, then add it to your page. E.g, in code:

MyPopupControl popup = (MyPopupControl)Page.LoadControl("/path/to/usercontrol.ascx");
PopupPanel.Controls.Add(popup);

Where PopupPanel is an empty <asp:Panel>. Then, not even the markup will need to be loaded/processed except when its needed.

There is no reason that all the code you use to display and process this panel couldn't also be in the usercontrol, isolating it from the master page.

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Can you build the panel dynamically, based on the cookie setting?