ASP.Net C# reference to element on Site.master returns: Object reference not set to an instance of an object

Question

I've found threads solving this issue within Default.aspx and Default.aspx.cs, but applying those solutions to my problem don't fix my issue. None of them are helpful in this context:

I'm trying to access an element on my Site.master page within Default.aspx.cs. I want to hide this element if a certain condition isn't met. However, I cannot reference any elements within my Site.master page (either within Default.aspx.cs OR Site.master.cs)

Code:

Site.master:

<li><a runat="server" id="editLink" href="~/Edit">Edit</a></li>

Default.aspx.cs:

MasterPage master = this.Master;
Control linkControl = master.FindControl("editLink");
linkControl.Visible = false;

I've also tried:

Site.master:

<asp:Panel ID="Panel1" runat="server">
    <li><a runat="server" id="editLink" href="~/Edit">Edit</a></li>
</asp:Panel>

Default.aspx.cs:

((Panel)Master.FindControl("Panel1")).Visible = false;
//or..
//Panel testPanel = ((Panel)Master.FindControl("Panel1"));
//Panel1.Visible = false;

I don't know where to start. Thanks!

EDIT:

I've tried to apply resolutions from:

ASP.NET - Accessing Master Page elements form the Content Page

What is a NullReferenceException, and how do I fix it?

Specifically from the first:

adding the following to Default.aspx

<%@ MasterType virtualpath="~/Site.master" %>

adding the following to Default.aspx.cs

Panel testPanel = (Panel)Master.FindControl("Panel1");       
testPanel.Visible = true;

The above code is the suggested fix for the first thread, but I get the same error. The second thread seemed to suggest I was referencing the element before it was created thus returning the nullreferenceexception error, but I do not believe this is the case. Ultimately, I do not understand enough to utilize those threads.

EDIT

Site.master MCVE:

<%@ Master Language="C#" AutoEventWireup="true" CodeFile="Site.master.cs" Inherits="SiteMaster" %>

<form id="wrapForm" runat="server">
    <asp:ScriptManager runat="server" EnablePageMethods="true"></asp:ScriptManager>
    <asp:ContentPlaceHolder ID="MainContent" runat="server">
      <asp:Panel ID="Panel1" runat="server">Test Text</asp:Panel>
    </asp:ContentPlaceHolder>
</form>

Default.aspx.cs MCVE:

protected void Page_Load(object sender, EventArgs e)
{
    Panel testPanel = (Panel)Master.FindControl("Panel1"); 
    testPanel.Visible = true;
}

Possible duplicate of [What is a NullReferenceException, and how do I fix it?](http://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-and-how-do-i-fix-it). Other possible duplicate: [ASP.NET - Accessing Master Page elements form the Content Page](http://stackoverflow.com/q/461911/1260204) — Igor, Feb 06 '17 at 15:57
You haven't shown the context of where the control is within a master page. Is it in another control? It helps to make an [MCVE](http://stackoverflow.com/help/mcve). — mason, Feb 06 '17 at 16:15
Maybe your development webserver is still loading the old assemblies? Could be an idea to shut down the server entirely and rebuild/run. — NicoE, Feb 06 '17 at 16:39
@mason I attempted to add an MCVE - stripped everything from Site.master and included just the Page_Load method from Default.aspx.cs. Please let me know if I've done this incorrectly. Thanks! — Skettenring, Feb 06 '17 at 17:02
@Igor Edited, as I do not believe either of those threads help - I'd attempted to utilize the solutions in those specific threads and they do not seem to help — Skettenring, Feb 06 '17 at 17:05
which is null at runtime? `Master`, or `testPanel`? could you include the markup of Default.aspx as well? — Cee McSharpface, Feb 06 '17 at 17:13
`MasterType` <= shouldn't that be `Reference` as per [ASP.NET - Accessing Master Page elements form the Content Page](http://stackoverflow.com/questions/461911/asp-net-accessing-master-page-elements-form-the-content-page) ? So `` — Igor, Feb 06 '17 at 17:15
Your MCVE is helpful (although still not complete). Why do you have the panel inside of a `ContentPlaceHolder`? Does your page have an `asp:Content` that corresponds to `MainContent`? — mason, Feb 06 '17 at 17:17
@Igor That was it. Thank you very much! (can I mark comments as solutions?) — Skettenring, Feb 06 '17 at 17:20
@mason the ContentPlaceHolder is referenced within Default.aspx and all other pages, so I don't have to add a header every time. I must have organized this in an odd way - changing my reference to the Master page made it so I can reference the panel, so now I'll start researching best practices for organization. Thank you! — Skettenring, Feb 06 '17 at 17:22
Content in a content place holder will not be included in the resulting page if the content page has a Content control corresponding to that content place holder. The content from the content page will overwrite it. — mason, Feb 06 '17 at 17:24
@Ninjutstu - Thanks for the update. No, you can't mark a comment as answer but I added it as an answer. — Igor, Feb 06 '17 at 17:43

score 1 · Accepted Answer · edited May 23 '17 at 11:45

1

MasterType <= that should be Reference as per ASP.NET - Accessing Master Page elements form the Content Page ?

<%@ Reference virtualpath="~/Site.master" %>

edited May 23 '17 at 11:45

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answered Feb 06 '17 at 17:42

Igor

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ASP.Net C# reference to element on Site.master returns: Object reference not set to an instance of an object

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