csharp one dimensional dictionary

                
                        // constant searching similar to dictionary but not in key/value pair
// NOTE: value represents the key itself, you can't store equal values
HashSet<T> constantSearch = new HashSet<T>();
var getValue = constantSearch[value as key];

// example
var usedNumbers = new HashSet<int>();
usedNumbers.Constains(number);
//
var registeredUsers = new HashSet<string>();
registeredUsers.Constains(userName);