/// <summary>
/// Adds items to the collection if they are not already present.
/// </summary>
/// <typeparam name="T">The type of the collection's elements and the items to add.</typeparam>
/// <param name="collection">The collection to which the items will be added.</param>
/// <param name="items">The items to add to the collection.</param>
public static void AddRangeIfNew <T>(this ICollection <T> collection, params T[] items)
{
collection.AddRangeIf(queriedItem => !collection.Contains(queriedItem), items);
}
/// <summary>
/// Adds items to the collection if they are not already present.
/// </summary>
/// <typeparam name="T">The type of the collection's elements and the items to add.</typeparam>
/// <param name="collection">The collection to which the items will be added.</param>
/// <param name="items">The items to add to the collection.</param>
public static void AddRangeIfNew <T>(this ICollection <T> collection, IEnumerable <T> items)
{
collection.AddRangeIf(queriedItem => !collection.Contains(queriedItem), items);
}
