This Class is useful for Creating FormAuthentication. 
using 
System;
using 
System.Collections.Generic;
using 
System.Linq;
using System.Web;
using 
System.Web.Security;
using 
System.Web.UI.WebControls;
using 
System.Web.UI.WebControls.WebParts;
using 
System.Web.UI.HtmlControls;
using 
System.Net.NetworkInformation;
using 
System.Management;
using 
System.Security.Principal;
namespace 
AIMS_Shared
{
    public class
FormAuthentication
    {
        public FormAuthentication()
        {
        }
        #region 
::This Method is use for creating Formauthentication ticket and cookie::
        public void 
CreateFormAuthenticationTicket(string userid,
string UserData, 
HttpResponse httpResponse)
        {
            // Create a new ticket used for 
authentication
            FormsAuthenticationTicket 
ticket = new 
FormsAuthenticationTicket(
            1, // Ticket version
            userid, // Username to be 
associated with this ticket
            DateTime.Now,
// Date/time issued
            DateTime.Now.AddHours(14),
// Date/time to expire
            true,
// "true" for a persistent user cookie (could be a 
checkbox on form)
            UserData, // User-data (the roles 
from this user record in our database)
            FormsAuthentication.FormsCookiePath);
// Path cookie is valid for
           
// Hash the cookie for transport over the wire
            string hash =
FormsAuthentication.Encrypt(ticket);
            HttpCookie cookie =
new HttpCookie(
            FormsAuthentication.FormsCookieName,
// Name of auth cookie (it's the name specified in 
web.config)
             hash); // 
Hashed ticket
            cookie.Expires =
DateTime.Now.AddHours(14);
            
            httpResponse.Cookies.Add(cookie);              
        }
        #endregion
        #region 
::This function is use for geting user identity information ::
        public string 
GetIdentity(System.Security.Principal.IIdentity 
iIdentity)
        {
            string userData =
"";
            FormsIdentity id = (FormsIdentity)iIdentity;
            FormsAuthenticationTicket ticket 
= id.Ticket;
            userData = ticket.UserData;
            return userData;
        }
        #endregion
       
public string 
GetCurrentSystemMACAddress()
        {            
            ManagementClass mc =
new ManagementClass("Win32_NetworkAdapterConfiguration");
            ManagementObjectCollection moc = 
mc.GetInstances();
            string MACAddress =
String.Empty;
            foreach (ManagementObject 
mo in moc)
            {
                if (MACAddress ==
String.Empty) // 
only return MAC Address from first card
                {
                    if ((bool)mo["IPEnabled"] 
== true) MACAddress = mo["MacAddress"].ToString();
                }
                mo.Dispose();
            }
            MACAddress = 
MACAddress.Replace(":",
"");
            return MACAddress;            
        }
       
public string 
GetCookieValue(HttpContext Context)
        {
            string CookieValue =
string.Empty;
            // Get the authentication cookie
            string cookieName =
FormsAuthentication.FormsCookieName;
            HttpCookie authCookie = 
Context.Request.Cookies[cookieName];
            // If the cookie can't be found, don't 
issue the ticket
            // if (authCookie 
== null) return;
           
// Get the authentication ticket and rebuild the 
principal 
            // & identity
            FormsAuthenticationTicket 
authTicket =
              FormsAuthentication.Decrypt(authCookie.Value);
            string[] roles = 
authTicket.UserData.Split(new
Char[] { '|' 
});
            //GenericIdentity userIdentity =
            //  new 
GenericIdentity(authTicket.Name);
            //GenericPrincipal userPrincipal =
            //  new 
GenericPrincipal(userIdentity, roles);
            //Context.User = userPrincipal;
            CookieValue = roles.ToString();
            return CookieValue;
        }
    }
}
You must Add  In your  
web.config file.
<authentication
mode="Forms">
      <forms
name="FormsAuthDB.AspxAuth"
loginUrl="UserLogin.aspx"
protection="All"
path="/"/>
    </authentication>