ASP.NET provides mechanisms for storing information for a single user session or across multiple sessions. This is done using the HttpSessionState and HttpApplicationState classes. The Page class has Application and Session attributes to provide access to current objects. The simple way to access them is as following:

if (Session["FirstName"] == null)
{
    LabelFirstName.Text = “FirstName”;
}
else
{
    LabelFirstName.Text = (string)Session["FirstName"];
}
if (Session["LastName"] == null)
{
    LabelLastName.Text = “LastName”;
}
else
{
    LabelLastName.Text = (string)Session["LastName"];
}

As we all know whenever we build an ASP.NET application with a MasterPage, all the controls receive a prefix such as “ctl00$<ContentPlaceHolderID>$<NameYouGaveToControl>”  to their names according to their place in the page hierarchy. That is done in order to prevent from two controls to have the same ID on the same page.
We encounter a problem [...]