how to make a variable communicate with more than one method ?

 How can I declare a variable, so it is accessible from all methods.
I currently have a page with radio buttons and a submit button. The idea is depending of which button you select it will go to a different email address:
 
Here is the code behind:
 
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Net.Mail;





public partial class admin_addUser : System.Web ...