/// <summary>
/// Adds an item to the collection if it is not already present.
/// </summary>
/// <param name="item">The item to add.</param>
public override void Add(T item)
{
if (-1 == DistinctListItems.IndexOf(item))
{
base.Add(item);
}
//else do nothing.
}
/// <summary>
/// Inserts an item into the collection at the specified index,
/// if the item is not already present.
/// </summary>
/// <param name="index">The index at which to insert the item.</param>
/// <param name="item">The item to insert into the collection.</param>
public override void Insert(int index, T item)
{
//Note: No error handling necessary.
// If the index is out of bounds, then let the list's insert method throw an exception.
if (-1 == DistinctListItems.IndexOf(item))
{
base.Insert(index, item);
}
//else do nothing.
}
/// <summary>
/// Gets or sets the item at the specified index,
/// unless the item already exists at another index.
/// </summary>
/// <param name="index">The zero-based index of the item to get or set.</param>
/// <returns>Returns the item at the specified index.</returns>
public override T this[int index]
{
get { return(base[index]); }
set
{
int currentIndex = DistinctListItems.IndexOf(value);
if (currentIndex == -1 || currentIndex == index)
{
base[index] = value;
}
//else do nothing.
}
}
