Question 88138 in ASP.NET Question posted in
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Cannot get inner HTML when trying to show div element – Asp.net

I am supporting a really old legacy application that is about to be taken down which is written in aspx. I have a <div> element inside a page (Example.aspx) that I am trying to make visible in the code behind (Example.aspx.cs) based on a checkbox checked value. However I keep getting this Cannot get inner content of '' because the contents are not literal error and thus my div is not being rendered. I referred to this SO post: Cannot get inner content of '' because the contents are not literal which mentions that this will not work on controls that are run on the server i.e runat="server". I cannot access the WordPress url referenced in the one answer from this SO post that was suggested: Cannot get inner HTML – and this one (Cannot manage to change the inner html of a div element) is not applicable to my question.

Example.aspx:

<div id="testID" runat="server"> <!--some content ---></div>

Example.aspx.cs:

 protected void checkBoxName_CheckedChanged(object sender, EventArgs e)
 {
      if(!checkBoxName.Checked)
           testID.Visible = true; //The exception is thrown here
 }
Tags:

2

Answers


  1. 0

    You haven’t shown the code for the CheckBox, but considering that you have an event handler for it, I assume you have something like the following:

    <asp:CheckBox id="checkBoxName" runat="server" OnCheckedChanged="checkBoxName_CheckedChanged" AutoPostBack="true" Checked="true" /> This is my CheckBox
<div class='myClass1' id="testID" runat="server">This is my DIV</div>

    in which case, the following should work:

    protected void checkBoxName_CheckedChanged(object sender, EventArgs e)
{
    CheckBox cBox = (CheckBox)sender;
    Control divCtrl = cBox.Parent.FindControl("testID");

    if (divCtrl != null)
    {
        //set value
        divCtrl.Visible = cBox.Checked;
    }
}

    This has been tested using the following:

    Create a new project – ASP .NET Web Application (.NET Framework)

    • For Project Name: CheckBoxTest
    • Click Create
    • Click Empty
    • Uncheck Configure for HTTPS (optional)
    • Click Create

    Open Solution Explorer

    • In VS menu, click View
    • Select Solution Explorer

    Add Web form

    • In Solution Explorer, right click <project name>
    • Click Add
    • Select New Item
    • Click Web Form (name: default.aspx)
    • Click Add

    default.aspx

    <%@ Page Language="C#" AutoEventWireup="true" CodeBehind="default.aspx.cs" Inherits="CheckBoxTest._default" %>

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
        <asp:CheckBox id="checkBoxName" runat="server" OnCheckedChanged="checkBoxName_CheckedChanged" AutoPostBack="true" Checked="true" /> This is my CheckBox
        <p />
        <div class='myClass1' id="testID" runat="server">This is my DIV</div>
    </form>
</body>
</html>

    default.aspx.cs:

    using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace CheckBoxTest
{
    public partial class _default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }

        protected void checkBoxName_CheckedChanged(object sender, EventArgs e)
        {
            CheckBox cBox = (CheckBox)sender;

            //find desired control
            Control divCtrl = cBox.Parent.FindControl("testID");

            if (divCtrl != null)
            {
                //set value
                divCtrl.Visible = cBox.Checked;
            }
        }
    }
}

    Resources:

    Additional Resources:

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  2. 0

    Ok, this looks to be as simple as possible.

    However, DO keep in mind that HTML rendering does NOT occur when you set a control visible = false.

    In other words, you set visible = false, then other code (in most cases client side) will not then see this "div" or whatever – since it not at all rendered.

    I don’t know what other code is involved here, but I would test/try/consider using style to hide, and thus the HTML is still there – but does not show.

    so, try this:

     testID.Style["display"] = "none";

    and to display, then

     testID.Style["display"] = "normal";

    However, perhaps some udpate panel is involved here – and that will change how this works. If the button/checkbox is say inside of a update panel, and the div is not? Then this will not work.

    However, if the button/checkbox is outside of the update panel, then it should work ok. So, if update panels are being used, this could effect behavours.

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