/// <summary>
/// Returns true if this set contains only the specified element.
/// </summary>
public bool IsSingleton(TElement element)
{
return(1 == Count && ElementEqualityComparer.Equals(_array[0], element));
}
protected virtual bool AreEquals(EqualityComparerContext context, T x, T y) => (!context.TryAdd(x) | !context.TryAdd(y)) || ElementEqualityComparer.Equals(x, y);
