/// <summary>
/// Sets the selection to only the passed item, if it is a possible choice.
/// </summary>
/// <param name="item">Item.</param>
public ListBox <T> SetSelected(T item)
{
if (_items.Contains(item))
{
_selection.Set(item);
}
else if (_selection.GetRequired() && _items.Count > 0)
{
_selection.Set(_items[0]);
}
else
{
_selection.Clear();
}
return(this);
}