隐藏母版页控件

Question

I want to hide master page table from the content page.

I have tried to hide the table control in different ways but I get following error message on line:

tbl = (HtmlTable)Page.Master.FindControl("tbl_login");

ERROR:

Object reference not set to an instance of an object.

Here is the table control on the master page and the code for hidding master page control from the login page.

There is a page called POView and it has got one link button to Approve PO and it shows POP up window which has got few controls defined one master page(text box and two button in html table) when you hit the button it sends the request to another page called Login which authenticate user password and do some updates in DB and then show the message to this POP up window (response.write).

All i want is to hide the controls (textbox and button defined on master page) from this login page.

NOTE: That Login page doesn't have any reference tag for the master page.

@ Page Language="C#" AutoEventWireup="true" CodeFile="login.aspx.cs" Inherits="login" %>

ADDED: Here is the function which is called onClick of Master page button. It is sending request to login page.

function showHint(str, str2, str3, reason)
{

gDiv = 'appFeedback';

xmlHttp=GetXmlHttpObject();
if (xmlHttp==null)
  {
  alert ("Your browser does not support AJAX!");
  return;
  }
  //replace "tricky" chars in QS
  var pwd=  str.replace('£','!!pound!!');
  pwd=  pwd.replace('£','!!pound!!');
  pwd=  pwd.replace('£','!!pound!!');
  pwd=  pwd.replace('£','!!pound!!');
  pwd=  pwd.replace('&','!!and!!');
  pwd=  pwd.replace('&','!!and!!');
  pwd=  pwd.replace('&','!!and!!');
  pwd=  pwd.replace('&','!!and!!');

var url="login.aspx";
url=url+"?q="+pwd;
url=url+"&q2="+str2;
url=url+"&q3="+str3;
url=url+"&reason="+reason;
url=url+"&entity=<%= Request["entity"] %>";
url=url+"&sid="+Math.random();

xmlHttp.onreadystatechange=stateChanged;
xmlHttp.open("GET",url,true);
xmlHttp.send(null);
}

Answer 1

Try To call this javascript After doing the login window.opener.document.getElementById("tbl_login").style.visibility="hidden";

In you code it is given as

xmlHttp.onreadystatechange=stateChanged;

Here the "stateChanged" must be a javascript function which will be fired after doing the login. Inside that function you can write the code to hide.

for more information about the readystatechangedevent please look into this :http://www.w3schools.com/ajax/ajax_xmlhttprequest_onreadystatechange.asp

Return success from Loginpage

//After doing the Logic return the status (foreg:- i return here as "success")
Response.Clear();
Response.ContentType = "text/plain";
Response.Write("success");
Response.End();

Answer 2

When content page have directive

<%@ MasterType VirtualPath="~/Main.Master" %>

you have access to content of master page. Now, if you make method on master page that just hidding your table - something like this

public void SetTableUnvisible()
{
    tbl_login.Visible = false;
}

you can call this method on Page_Load event of content page

Master.SetTableUnvisible();

and your table is no more visible.

Answer 3

It sounds like you're trying to always remove the table, even though one or more pages don't even contain the table since they don't reference the master page anyway. Is that correct?

If so, your code will be falling over because you're dereferencing Page.Master anyway, even though it won't always exist. Try this, which checks to see whether there is a master page before trying to use it:

MasterPage master = Page.Master;
if (master != null)
{
    tbl = master.FindControl("tbl_login") as HtmlTable;
    if (tbl != null)
    {
        tbl.IsVisible = false;
    }
}

Answer 4

If your login page doesn't use the master page then you can't do it on server but with client side code only. Make a script method that hides the table. You can insert it in the master page:

<script type="text/javascript">
function hideTable()
{
   $('#<%=tbl_login.ClientID%>').hide();
}
</script>

In the login page:

ClientScript.RegisterStartupScript(this.GetType(), "hide", "hideTable();", true);

BTW, if you want to do anything in the master page, don't try to find controls on it from your page. Write a method in the master page that do it and call it from your page. You'll need to cast Master to the master type, or put a master type in the master directive that do it for you.