c# - 为 LinkedList 类实现 C# IEnumerable<T>

Question

我正在尝试在 Linux 上使用 monoDevelop 在 C# 中编写自定义 LinkedList 类，只是为了测试和学习。下面的代码永远不会编译，我不知道为什么!!它甚至不告诉我出了什么问题。它只是说:错误:编译器似乎已崩溃。检查构建输出板以获取详细信息。当我去检查输出板时，它也没有帮助: 未处理的异常:System.ArgumentException:必须在泛型类型定义上声明指定的字段。 参数名称:字段

我能做什么？

using System;
using System.Text;
using System.Collections.Generic;

namespace LinkedList
{
    public class myLinkedList<T> : IEnumerable<T>
    {
        //List Node class
        //===============
        private class ListNode<T>
        {
            public T data;
            public ListNode<T> next;

            public ListNode(T d)
            {
                this.data = d;
                this.next = null;
            }

            public ListNode(T d, ListNode<T> n)
            {
                this.data = d;
                this.next = n;
            }
        }

        //priavte fields
        //===============
        private ListNode<T> front;
        private int size;

        //Constructor
        //===========
        public myLinkedList ()
        {
            front = null;
            size = 0;
        }


        //public methods
        //===============
        public bool isEmpty()
        {
            return (size == 0);
        }

        public bool addFront(T element)
        {
            front = new ListNode<T>(element, front);
            size++;
            return true;
        }

        public bool addBack(T element)
        {
            ListNode<T> current = front;
            while (current.next != null)
            {
                current = current.next;
            }

            current.next = new ListNode<T>(element);
            size++;
            return true;
        }

        public override string ToString()
        {
            ListNode<T> current = front;
            if(current == null)
            {
                return "**** Empty ****";
            }
            else
            {
                StringBuilder sb = new StringBuilder();
                while (current.next != null)
                {
                    sb.Append(current.data + ", ");
                    current = current.next;
                }
                sb.Append(current.data);

                return sb.ToString();
            }
        }

        // These make myLinkedList<T> implement IEnumerable<T> allowing
        // a LinkedList to be used in a foreach statement.
        public IEnumerator<T> GetEnumerator()
        {
            return new myLinkedListIterator<T>(front);
        }


        private class myLinkedListIterator<T> : IEnumerator<T>
        {
            private ListNode<T> current;
            public virtual T Current
            {
                get
                {
                    return current.data;
                }
            }
            private ListNode<T> front;

            public myLinkedListIterator(ListNode<T> f)
            {
                front = f;
                current = front;
            }

            public bool MoveNext()
            {
                if(current.next != null)
                {
                    current = current.next;
                    return true;
                }
                else
                {
                    return false;
                }
            }

            public void Reset()
            {
                current = front;
            }

            public void Dispose()
            {
                throw new Exception("Unsupported Operation");
            }
        }
    }
}

Answer 1

您需要添加非通用API；所以添加到迭代器:

object System.Collections.IEnumerator.Current { get { return Current;  } }

和可枚举的:

System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
{
    return GetEnumerator();
}

然而!如果您手动执行此操作，那么您就错过了一个技巧。 “迭代器 block ”会容易得多。

下面是一个完整的实现；您根本不需要编写枚举器类(您可以完全删除 myLinkedListIterator<T>):

public IEnumerator<T> GetEnumerator()
{
    var node = front;
    while(node != null)
    {
        yield return node.data;
        node = node.next;
    }
}
System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
{
    return GetEnumerator();
}