Handling session in common place in asp.net

Can we handle all session in a single static class like ?

public static class SessionManager
{
// Will it be a problem to assign a object like this?
public static Criteria SearchCriteria
{
   get{
      Criteria searchCriteria = HttpContext.Current.Session["SearchCriteria"] as Criteria;
    if(searchCriteria ==null)
     {
       searchCriteria =new Criteria();
     }
   return searchCriteria ;
   }
set{
      HttpContext.Current.Session["SearchCriteria"] =value;
     }
}
// Will it be a problem to assign a string like this?
public static string UserName
{
   get{
      string userName= HttpContext.Current.Session["UserName"] as string;
    if(string.IsNullOrEmpty(IsuserName))
     {
        userName=<<CurrentUser>>;
     }
    return userName;
   }
set{
      HttpContext.Current.Session["userName"] =value;
     }
}

}

is this a good idea ?