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Accessing masterpage code behind code from a child pages .ASPX page

I'm looking to execute code in my code behind on my Masterpage, and use it on the .aspx page of child pages like Default.aspx, without having to call it through the Default.aspx.cs page.
This is my attempt by accessing it like so <% MasterPage.getPlanCost() %>, however, this does not work. As there's "no definition" for getPlanCost()
Master Page code behind:
public string getPlanCost()
{
var country = getCountry();
string gbp = "£5.99";
string euro = "€6.99";
string usd = "$8.99";
var currencyCost = usd;
if (country == "United Kingdom") // gbp
{
currencyCost = gbp;
}
else if (country == "United States" || country == "Canada" || country == "Australia" || country == "New Zealand") // usd
{
currencyCost = usd;
}
else // euro
{
currencyCost = euro;
}
return currencyCost;
}
Default.aspx page:
<p class="text-center under-title text-muted"><%=MasterPage.getPlanCost() %> Cancel Anytime.</p>
What is the quickest / most efficient way of achieving this? Furthermore, I have tried to use alternate methods seen on StackOverflow, using get and set however I was unable to get this working. Fairly new to C# so I apologise.

Although you have found a workaround, it is possible to access master page methods from child web forms, useful in cases where want your child page to affect the master page in some way. You can do this through the Page.Master property, but you will first have to register the type or cast it.
Method 1: Registering Master Type
Web Form:
<%# Page Language="C#" MasterPageFile="~/Example.Master" ... %>
<%# MasterType VirtualPath="~/Example.Master" %>
Code Behind:
Page.Master.getPlanCost();
Method 2: Casting Master Property
Code Behind:
((Example)Page.Master).getPlanCost();

To anybody wondering, I created a class called Utilities.cs
Then called it directly from here from my Default.aspx page instead.
<%=Utilities.getPlanCost()%>
I'd also like to thank #Joel Coehoorn for his comments which got me halfway there.

accessing a user control from masterpage

I have a user control in my master page under the login view under the Role groups.Here is the control.Its not in the content placeholder.However if i try to access it i get null result.How can i access this from my page code behind.I am having problem getting it from master page.
<asp:RoleGroup Roles="Students">
<ContentTemplate>
<uc1:studentsPanel runat="server" ID="studentcontrol" />
</ContentTemplate>
</asp:RoleGroup>
Here is how i am having my code
LoginView control = Page.Master.FindControl("studentcontrol") as LoginView;
if (control != null)
{
Label1.Text = "found";
}

Here's the code I use to get to controls in MasterPages
//Master page from user control
LoginControl control
Page page = (Page)this.Page;
MasterPage master = (MasterPage)page.Master;
control= (LoginControl )master.FindControl("studentcontrol");
if (control!= null)
{
Label1.Text = "found";
}

We can't see the whole code, but your snippets seem correct. Try first not to cast your control to LoginView - the reason might be that your panel is not of that type. To try out if the control is found at all, use
if(Page.Master.FindControl("studentcontrol") != null) {
Label1.Text = "found";
}
first before adding another possible source of failure.
There's two more explicit answers that don't need to be repeated here. You find wonderful explanations here and here.

as #Krishnraj said,
i dont know which is control within studentsPanel UserControl, but i assume that Label. You should access like that,
var Loginview = (Master.FindControl("LoginView1") as LoginView);
Control cont = new Control();
Loginview.RoleGroups[0].ContentTemplate.InstantiateIn(cont);
(cont.Controls[1].FindControl("_trylbl") as Label).Text = "Hello say";

how to update masterpage elements from child page in asp.net

I want to update master page hyperlinks from child page. Here is the code i written to update
master page elements.
HyperLink h1 = this.Master.FindControl("AnLogin") as HyperLink;
h1.NavigateUrl = "#";
h1.Text = Session["UserName"].ToString();
HyperLink h2 = this.Master.FindControl("AnLogout") as HyperLink;
h2.Text = "Logout";
h2.NavigateUrl = "~/Logout.aspx";
if (Session["UserType"].ToString() == "Admin")
{
Response.Redirect("~/Admin.aspx");
}
Master page is updating only when i am not redirecting to another page. If i am redirecting to another page, that hyperlinks remain same as static.
Here i need to update master page hyperlinks that should be same for all pages further i can traverse. How to accomplish this?

Here i suggest not to post back the page for such small operations.
You can set this condition on aspx page like :-
<% if (Session["UserType"].ToString() == "Admin") {%>
// do something
<%} else { %>
// do something
<%} %>

Accessing RadEditor control from master page's code behind...its not finding any radEditor control when it is there..whats wrong?

Its not executing statements in if block in my method
Master Page:-
page load event:-
Control c = new Control();
DoSomething(c);
My method:-
protected void DoSomething(Control control)(
{
foreach (Control c in control.Controls)
{
if(typeof(c).Equals(Telerik.Web.UI.RadEditor))
{
Telerik.Web.UI.RadEditor rad = c as Telerik.Web.UI.RadEditor;
label1.Visible = true; label1.Text = "dhchk";
rad.CssFiles.Add("~/styles/myStyle.css");
rad.CssFiles.Add("~/styles/myStyle2.css");
rad.CssFiles.Add("~/styles/myStyle3.css");
}
else
{
DoSomething(c);
}
}
}
my content page:-
<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">
<telerik:RadEditor ID="Editor1" EnableEmbeddedBaseStylesheet="false" EnableEmbeddedSkins=false runat="server">
</telerik:RadEditor>
<telerik:RadEditor ID="Editor2" EnableEmbeddedBaseStylesheet="false" EnableEmbeddedSkins=false runat="server">
</telerik:RadEditor>
[EDIT] ok when debugging..I rt clicked "c" and then Quick watch...it says "The name 'c' does not exist in the current context" (?!?!) how so ?

Well, the Master page renders first so you won't have access from the master page to any of the content page controls. You can achive this using events and passing the control from the content to the master
udpate:
Again - Accessing user controls from the master page is flaw in the whole master->content design. the closest thing I can imagine is adding static function
public static void AddDesign(RadEditor obj)
{
...
}
and then call the function form the Page_Load of the user control
MASTER_PAGE_CLASS_NAME.AddDesign(RadEditor1);

Well, I'm not sure, you can access controls in page like this.
At first: that editor should be probably in some Panel (or some other container), so i should look like this:
<asp:Panel ID="pnl1" runat="server">
<telerik:RadEditor ID="Editor1" EnableEmbeddedBaseStylesheet="false" EnableEmbeddedSkins=false runat="server" />
<telerik:RadEditor ID="Editor2" EnableEmbeddedBaseStylesheet="false" EnableEmbeddedSkins=false runat="server" />
</asp:Panel>
Then try this:
protected void Page_Load(object sender, EventArgs e)
{
foreach (Controls c in pnl1.Controls)
{
if (c is Telerik.Web.UI.RadEditor)
{
// do you stuff ...
}
}
}

You should change things around and call your MasterPage method from the content control.
In your masterpage add the method:
public void DoSomething(Telerik.Web.UI.RadEditor rad)
{
label1.Visible = true; label1.Text = "dhchk";
rad.CssFiles.Add("~/styles/myStyle.css");
rad.CssFiles.Add("~/styles/myStyle2.css");
rad.CssFiles.Add("~/styles/myStyle3.css");
}
Call the function from an appropriate event in your page/content control. eg Page.Load, Editor1.Load etc
Master.DoSomething(Editor1);
Update
From the masterpage, you should search for child controls in the Content controls
ContentPlaceHolder1.FindControl("Editor1");
or you could try something like:
foreach (Control c in ContentPlaceHolder1.Controls)
{
if(typeof(c).Equals(Telerik.Web.UI.RadEditor))
{
Telerik.Web.UI.RadEditor rad = c as Telerik.Web.UI.RadEditor;
label1.Visible = true; label1.Text = "dhchk";
rad.CssFiles.Add("~/styles/myStyle.css");
rad.CssFiles.Add("~/styles/myStyle2.css");
rad.CssFiles.Add("~/styles/myStyle3.css");
}
else
{
DoSomething(c);
}
}

The load and render events of the master page are fired after those of the content page (as said here). Hence the controls in the content page should be available by the time these two events are fired?

Simple user control for conditionally rendering nested HTML

What I would like to do, is be able to pass two attributes to a user control, a ListName and a Permission, like so:
<uc:check id="uc" List="Shared Documents" Permission="OpenItems" runat="server">
<!-- have some HTML content here that is rendered if the permission is true -->
</uc:check>
Then in the actual check user control, have something similar to:
<%# Control language="C#" ClassName="check" %>
<%
// determine permission magic placeholder
if (DoesUserHavePermissions(perm))
{
// render nested HTML content
}
else
{
// abort rendering as to not show nested HTML content
}
%>
I have read the page on creating a templated control on MSDN, and while that would work - it really seems to be a bit overkill for what I am trying to do. Is there a control that already renders content based on a boolean expression or a simpler template example?
http://msdn.microsoft.com/en-us/library/36574bf6.aspx
Update:
The following code can be used in the ascx to model a very simple version of this:
<%# Control Language="C#" ClassName="PermissionCheck" %>
<%# Import Namespace="System.ComponentModel" %>
<script runat="server">
void Page_Init()
{
if (Allowed != null)
{
Panel container = new Panel();
Allowed.InstantiateIn(container);
PermissionBasedMessage.Controls.Add(container);
}
}
[PersistenceMode(PersistenceMode.InnerProperty)]
public ITemplate Allowed { get; set; }
</script>
<asp:Placeholder runat="server" ID="PermissionBasedMessage" />
Note: I oversimplified the check in the Page_Init method for this sample code. Additional logic checks can be added as needed.
And reference it in the calling HTML page:
<%# Register src="PermissionCheck.ascx" tagname="PermissionCheck" tagprefix="uc1" %>
<uc1:PermissionCheck ID="PermissionCheck1" runat="server">
<Allowed>Allowed Access</Allowed>
</uc1:PermissionCheck>

You could create a custom control instead of a user control: derive from the asp.net panel, add your two properties, then only render the control if the user has the required permission. E.g. something like this:
The control (put this in App_Code for example):
namespace MyControls
{
public class MyPanel : Panel
{
public string Permission { get; set; }
public string List { get; set; }
protected override void Render(System.Web.UI.HtmlTextWriter writer)
{
if (UserHasPermission()) base.Render(writer);
}
}
}
Using the control:
<%# Page ... %>
<%# Register Namespace="MyControls" TagPrefix="mc" %>
<html>
...
<mc:MyPanel runat="server" List="Shared Documents" Permission="OpenItems">
put content and/or other controls here
</mc:MyPanel>
...

Why don't you extend the LiteralControl, add properties for your settings, then render html to the .Value of the LieralControl? Seems pretty simple and a lot less of a headache than using Templated controls

The other answers are good for the generic form of your question, but for checking permissions SPSecurityTrimmedControl might do what you need.

Wrap your content with a place holder control and set the control's visibility to true or false (controls that have .Visible = false won't render any html)
<asp:PlaceHolder id="phWrapper" runat="server">
...
</asp:PlaceHolder>
Then in your code-behind set phWrapper.Visible = DoesUserHavePermissions(perm);
Hope that helps!