I am having this exception that I can't figure out why it is happening. I searched this site and others trying to find a solution but none have worked so far.
The Problem
I have the following two div in my .aspx page.
<div ID="success" style="visibility:hidden" runat="server">
// buttons and textfields
</div>
<div ID="fail" style="visibility:hidden" runat="server">
// buttons and textfields
</div>
On page load, I want one to become Visible depending on some criterion. But when I try to target them in code behind to change their visibility, it gives me a NullReferenceException pointing to the code trying to change their visibility.
The Code
This is the code I'm using in the code behind.
fail.Style.Add("visibility", "hidden");
success.Style.Add("visibility", "Visible");
I have also tried:
fail.Attributes.Add("style", "visibility:Visible");
success.Attributes.Add("style", "visibility:Visible");
I have done this exact same action on another .aspx page and it didn't give me this NullReferenceException on that page. So I have no idea what's going on. Can someone help please?
The code for newBin.aspx.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Configuration;
using System.Data.SqlClient;
using System.Data;
using System.Data.Common;
namespace SMTInventory
{
public partial class newBin : Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (Page.PreviousPage != null)
{
HiddenField pkid_box = (HiddenField)Page.PreviousPage.FindControl("locationID");
string pkid = pkid_box.Value;
locationID.Value = pkid;
success.Style.Add("visibility", "Visible");
}
else
{
if (Page.FindControl("fail") != null)
{
fail.Style.Add("visibility", "hidden");
success.Style.Add("visibility", "Visible");
}
else
{
fail.Style.Add("visibility", "hidden");
success.Style.Add("visibility", "Visible");
}
}
}
protected void btnNewLocation_Click(object sender, EventArgs e)
{
Server.Transfer("newLocation.aspx", true);
}
protected void btnNewBin_Click(object sender, EventArgs e)
{
}
}
}
The code for newBin.aspx
<%@ Page Title="New Bin" Language="C#" MasterPageFile="~/Site.Master" AutoEventWireup="true" CodeBehind="newBin.aspx.cs" Inherits="SMTInventory.newBin" %>
<asp:Content runat="server" ID="BodyContent" ContentPlaceHolderID="MainContent">
<hgroup class="title">
<h1><%: Title %>.</h1>
<h2>Add a New Bin</h2>
</hgroup>
<article>
<div ID="success" style="visibility:hidden" runat="server">
<asp:HiddenField ID="locationID" value="" runat="server" />
How many racks are in this bin? <asp:TextBox ID="binCount" runat="server" /><br />
<asp:button id="btnNewBin" onclick="btnNewBin_Click" runat="server" text="Add Bin" />
</div>
<div ID="fail" style="visibility:hidden" runat="server">
<p>This page cannot be used without first creating a new location.<br /></p>
<asp:Button ID="btnNewLocation" onclick="btnNewLocation_Click" runat="server" Text="Create New Location" />
</div>
</article>
<aside>
<h3>Aside Title</h3>
<p>
Use this area to provide additional information.
</p>
<ul>
<li><a runat="server" href="~/">Home</a></li>
<li><a runat="server" href="~/About">About</a></li>
<li><a runat="server" href="~/Contact">Contact</a></li>
</ul>
</aside>
</asp:Content>
Part of Site.Master
<div id="body">
<asp:LoginView runat="server" ViewStateMode="Disabled">
<AnonymousTemplate>
<asp:ContentPlaceHolder runat="server" ID="FeaturedContent" />
<section class="content-wrapper main-content clear-fix">
<asp:ContentPlaceHolder runat="server" ID="MainContent" />
</section>
<asp:ContentPlaceHolder runat="server" ID="NewContent" />
</AnonymousTemplate>
<LoggedInTemplate>
</LoggedInTemplate>
</asp:LoginView>
</div>
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