/// <summary>
/// Gets the item by the specified <paramref name="key"/>.
/// </summary>
/// <param name="key">The <see cref="UniqueKey"/>.</param>
/// <returns>The item where found; otherwise, <c>null</c>.</returns>
public TEntity GetByUniqueKey(UniqueKey key)
{
return(Items.Where(x => x.HasUniqueKey && key.Equals(x.UniqueKey)).FirstOrDefault());
}
/// <summary>
/// Gets the item by the specified <paramref name="key"/>.
/// </summary>
/// <param name="key">The <see cref="UniqueKey"/>.</param>
/// <returns>The item where found; otherwise, <c>null</c>.</returns>
public TEntity GetByUniqueKey(UniqueKey key)
{
Check.NotNull(key, nameof(key));
return(Items.Where(x => x.HasUniqueKey && key.Equals(x.UniqueKey)).FirstOrDefault());
}