C# linkedlist如何获取最后一个元素之前的元素

发布于 2024-10-12 01:53:45 字数 846 浏览 1 评论 0原文

我尝试在我的 Windows 窗体应用程序中实现重做撤消。

我建立了一个链表，列表中的每个条目都是一个类，用于保存表单中所有元素的状态。

每次单击保存按钮，都会将表单元素的最后状态插入到此列表中。

当用户单击撤消按钮时，我想获取列表的输入（最后一个之前的一个）并加载它。

我不知道在链表中的元素之前获取这个的简单方法是什么？

我的代码如下所示：

 public class SaveState {

          public int comboBox1;
          public int comboBox2;
          ..........
          public SaveState() {
           .......
          }
    }
    LinkedList<SaveState> RedoUndo = new LinkedList<SaveState>();

    # in save function
    var this_state = new SaveState();           
    this_state = getAllState();
    RedoUndo.AddLast(this_state);

    # when click undo
    var cur_state = new SaveState();
    # this lines dont work !!!!!!!!!
    int get = RedoUndo.Count - 1;        
    cur_state = RedoUndo.Find(get);
    setAllState(cur_state);

原文

i try to implement a redo undo in my windows form application.

i build a linkedlist , every entery of the list is a class that save the state of all the elemnts in the form.

every click on the save button , insert to this list the last state of the form elements.

when the user click on undo button i want to get the entery of the list (one before the last)
and load it.

i dont know what is the simple way to get this one before elemnts from the linked list ?

my code like look like:

 public class SaveState {

          public int comboBox1;
          public int comboBox2;
          ..........
          public SaveState() {
           .......
          }
    }
    LinkedList<SaveState> RedoUndo = new LinkedList<SaveState>();

    # in save function
    var this_state = new SaveState();           
    this_state = getAllState();
    RedoUndo.AddLast(this_state);

    # when click undo
    var cur_state = new SaveState();
    # this lines dont work !!!!!!!!!
    int get = RedoUndo.Count - 1;        
    cur_state = RedoUndo.Find(get);
    setAllState(cur_state);

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放肆 2024-10-19 01:53:45

您可以通过 LinkedList.Last

// list is LinkedList<T> for some T
var last = list.Last;

和倒数第二个节点通过 LinkedListNode.Previous

var penultimate = last.Previous; // or list.Last.Previous;

请注意，这是一个 LinkedListNode;并且您需要使用 LinkedListNode< ;T>.Value 属性获取 T 的底层实例。

当然，您应该注意检查 list 是否不为 null，并且 list.Last 是否不为 null（在空列表的情况下），并且 >list.Last.Previous 不为空（在单元素列表的情况下）。

You can get the last node via LinkedList<T>.Last

// list is LinkedList<T> for some T
var last = list.Last;

and the penultimate node via LinkedListNode<T>.Previous

var penultimate = last.Previous; // or list.Last.Previous;

Note that this is a LinkedListNode<T> and you need to use the LinkedListNode<T>.Value property get the underlying instance of T.

Of course, you should take care to check that list is not null, and list.Last is not null (in the case of an empty list), and that list.Last.Previous is not null (in the case of a single-element list).

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