foreach中使用Remove和Add_mst

1.删除第二个数据时开始报错，因为list长度发生了变化，会报错

List<string> list = new List<string>() { "a","b","c","d","e","f","g","h"};
Console.WriteLine("加入数据长度：" + list.Count.ToString());
foreach (var item in list)
{
    //list.Remove(item);
    Console.WriteLine("Remove的数据：" + item);
}
Console.WriteLine("Remove后的数据长度：" + list.Count.ToString());

2.解决方法：

2.1 for 倒叙遍历删除

//构造list
List<string> tempList = new List<string>() { "a", "b", "c", "d" };
//打印现有list
tempList.ForEach(p => {
    Console.WriteLine("tempList中的数据：" + p + ",");
});
//删除list数据，必须倒叙，正序可能会导致删除不完全
for (int i = tempList.Count - 1; i >= 0; i--)
{
    //删除所有
    tempList.Remove(tempList[i]);
    
    //删除 b
    //if (tempList[i] == "b")
    //{
    //    tempList.Remove(tempList[i]);
    //}
}
//打印剩余list数据
tempList.ForEach(p => {
    Console.WriteLine("tempList剩余数据：" + p + ",");
});

2.2 递归 原理是删除后重新读取list 这样就不会因为长度变化而报错

List<string> tempList1 = new List<string>() { "a", "b", "c", "d", "c", "f", "g", "c", "m" };

RemoveTest(tempList1);

tempList1.ForEach(p => {
    Console.WriteLine("使用递归删除c,剩余：" + p + ",");
});
//递归方法
static void RemoveTest(List<string> list)
{
    foreach (var item in list)
    {
        if (item == "c")
        {
            list.Remove(item);
            RemoveTest(list);
            return;
        }
    }
}

2.3 用泛型IEnumerator

RemoveClass<Groups> tempListie = new RemoveClass<Groups>();
tempListie.Add(new Groups() { id = 1, name = "Group1" });
tempListie.Add(new Groups() { id = 2, name = "Group2" });
tempListie.Add(new Groups() { id = 2, name = "Group2" });
tempListie.Add(new Groups() { id = 3, name = "Group3" });
foreach (Groups item in tempListie)
{
    if (item.id == 2)
    {
        tempListie.Remove(item);
    }
}

2.3.1 新建一个接口类 RemoveClass.cs

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Zoo
{
    public class RemoveClass<T>
    {
        RemoveClassCollection<T> collection = new RemoveClassCollection<T>();
        public IEnumerator GetEnumerator()
        {
            return collection;
        }
        public void Remove(T t)
        {
            collection.Remove(t);
        }
        public void Add(T t)
        {
            collection.Add(t);
        }
    }
    public class RemoveClassCollection<T> : IEnumerator
    {
        List<T> list = new List<T>();
        public object current = null;
        Random rd = new Random();
        public object Current
        {
            get { return current; }
        }
        int icout = 0;
        public bool MoveNext()
        {
            if (icout >= list.Count)
            {
                return false;
            }
            else
            {
                current = list[icout];
                icout++;
                return true;
            }
        }
        public void Reset()
        {
            icout = 0;
        }
        public void Add(T t)
        {
            list.Add(t);
        }
        public void Remove(T t)
        {
            if (list.Contains(t))
            {
                if (list.IndexOf(t) <= icout)
                {
                    icout--;
                }
                list.Remove(t);
            }
        }
    }

    public class Groups
    {
        public int id { get; set; }
        public string name { get; set; }
    }
}