public override string ToString()
{
DoubleLinkedItem currentLink = _first;
StringBuilder builder = new StringBuilder();
while (currentLink != null)
{
builder.Append(currentLink);
currentLink = currentLink.NextLink;
}
return(builder.ToString());
}
public DoubleLinkedItem Insert(string title)
{
// Creates a link, sets its link to the first item and then makes this the first item in the list.
DoubleLinkedItem link = new DoubleLinkedItem(title);
link.NextLink = _first;
if (_first != null)
{
_first.PreviousLink = link;
}
_first = link;
return(link);
}
public DoubleLinkedItem Delete()
{
// Gets the first item, and sets it to be the one it is linked to
DoubleLinkedItem temp = _first;
if (_first != null)
{
_first = _first.NextLink;
if (_first != null)
{
_first.PreviousLink = null;
}
}
return(temp);
}
///// New operations
public void InsertAfter(DoubleLinkedItem link, string title)
{
if (link == null || string.IsNullOrEmpty(title))
{
return;
}
DoubleLinkedItem newLink = new DoubleLinkedItem(title);
newLink.PreviousLink = link;
// Update the 'after' link's next reference, so its previous points to the new one
if (link.NextLink != null)
{
link.NextLink.PreviousLink = newLink;
}
// Steal the next link of the node, and set the after so it links to our new one
newLink.NextLink = link.NextLink;
link.NextLink = newLink;
}
public DoubleLinkedList()
{
_first = null;
}