/// <summary>
/// Returns a wrapper for the specified <see cref="Vector2DArrayList"/>
/// ensuring that all elements are unique.
/// </summary>
/// <param name="collection">The <see cref="Vector2DArrayList"/> to wrap.</param>
/// <returns>
/// A wrapper around <paramref name="collection"/> ensuring that all elements are unique.
/// </returns>
/// <exception cref="ArgumentException">
/// <paramref name="collection"/> contains duplicate elements.</exception>
/// <exception cref="ArgumentNullException">
/// <paramref name="collection"/> is a null reference.</exception>
/// <remarks><para>
/// The <b>Unique</b> wrapper provides a set-like collection by ensuring
/// that all elements in the <see cref="Vector2DArrayList"/> are unique.
/// </para><para>
/// <b>Unique</b> raises an <see cref="ArgumentException"/> if the specified
/// <paramref name="collection"/> contains any duplicate elements. The returned
/// wrapper raises a <see cref="NotSupportedException"/> whenever the user attempts
/// to add an element that is already contained in the <b>Vector2DArrayList</b>.
/// </para><para>
/// <strong>Note:</strong> The <b>Unique</b> wrapper reflects any changes made
/// to the underlying <paramref name="collection"/>, including the possible
/// creation of duplicate elements. The uniqueness of all elements is therefore
/// no longer assured if the underlying collection is manipulated directly.
/// </para></remarks>
public static Vector2DArrayList Unique(Vector2DArrayList collection)
{
if (collection == null)
throw new ArgumentNullException("collection");
for (int i = collection.Count - 1; i > 0; i--)
if (collection.IndexOf(collection[i]) < i)
throw new ArgumentException("collection",
"Argument cannot contain duplicate elements.");
return new UniqueList(collection);
}
