How to save UserId and use it my entire application

Hi,

In login.aspx.cs, I have assign session variables like as follows, both id and branchId has vales while debug,

HttpContext.Current.Session["userId"] = objusr.Id;  
HttpContext.Current.Session["branchId"] = objusr.BranchId;

If i am accessing these session variable on another page it shows empty.

int BId = Convert.ToInt32(HttpContext.Current.Session["branchId"].ToString()); // It shows 0 while debug

How to maintain and access these Id's to my whole application in asp.net 4.0

Is it anyother way?