Create Dictionary

 static Dictionary<string, int> roles = new Dictionary<string, int>();

 public static Dictionary<string, int> SetRoles(List<string> items)
           {
               if (roles != null)
               {
                   roles.Clear();
               }
               foreach (string item in items)
               {
                  // var Entitytype = item.Split('_')[1];
                   var country = item.Split('_')[2];
                  
                   string Session_osoid = db.View_SharePointMappingTable.Where(x => x.GroupName == item).FirstOrDefault().OsoID.ToString();
                   var Session_Priority = db.View_SharePointMappingTable.Where(x => x.GroupName == item).FirstOrDefault().Priority;

                   var role = item.Split('_')[3];
                   if (!roles.Keys.Contains(Session_osoid) || Session_Priority > roles[Session_osoid])
                       roles[Session_osoid] =Convert.ToInt32(Session_Priority);
               }
               return roles;
           }



Calling Dictionary


  Dictionary<string, int> roles;

  List<string> items = null;
                       
                        keyList = null;
                        priorityList = null;

                        items = Session["AuthenticateOso"].ToString().Split(',').ToList();
                        if (roles!=null)
                        {
                            roles.Clear();
                        }
                        roles = Appcommon.SetRoles(items);
                        var OsoidList = roles.Keys;
                        var Priority = roles.Values.ToArray();
                        keyList = roles.Keys.ToArray();

                        priorityList = Priority;