在“副本"上所做的更改列表反映了原始列表-C# [英] Changes made on "copy" list are reflecting original list - c#

问题描述

我有两个列表，原始列表和副本列表.由于以下原因，我制作了一份原始清单的副本:

I have two lists, the original one and a copied one. I made a copy of the original list, because of one reason:

我需要处理/处理原始列表中的数据，但我不应该对其进行编辑.因此，我创建了该原始列表的副本以供使用.但是我以某种方式对复制列表进行的更改仍然会修改原始列表.

I need to process/work data from the original list, but I shouldn't edit it. So I created a copy of that original list to work with. But somehow changes I do on the copied list still modifies the original.

这是我的代码:

forPrintKitchenOrders = new List<OrderTemp>();
foreach (var itemss in forPrintKitchen)
{
  forPrintKitchenOrders.Add(itemss); // HERE I AM ADDING ITEMS TO ANOTHER LIST BECAUSE I DON'T WANT TO EDIT ORIGINAL LIST (Change quantity etc)
}

if (forPrintKitchen.Count > 0)
{

  foreach (var item in forPrintKitchenOrders.ToList())
  {
      foreach (var item2 in mainList)
      {
          if (item2.MainProductID == Convert.ToInt32(item._articleCode))
          {
              //I don't know why this is happening. I loop another list (copy of original list, because I didn't want to harm original list), and when I find certain item I am reducing quantity (-1),
              //And later I realized and saw while I was debugging, that the value of quantity in my original "forPrintKitchen" list is also edited, I don't know how changed reflected there..

              int calculate = Convert.ToInt32(item._quantity)-1; //this block is making me trouble, here I am reducing quantity and later that reflects to my forPrintKitchen list even if I am editing and looping //forPrintKitchenOrders(original's copy)
              item._quantity = calculate.ToString();
          }
      }
  }
    foreach (var items in forPrintKitchen) //THIS IS MY ORIGILAN LIST AND SHE SHOULD NOT BE EDITED WHEN I EDIT "forPrintKitchenOrders" item
    {
    //Original List
        OrdersKitchen kitchen = new OrdersKitchen();
        kitchen.ProductID = Convert.ToInt32(items._articleCode);
        kitchen.UserID = Util.User.UserID;
        kitchen.UserName = Util.User.FirstName
        kitchen.LastName = Util.User.LastName
        kitchen.BillID = bill.BillID;
        kitchen.Quantity = Convert.ToInt32(items._Quantity);
        OrdersKitchen.Add(kitchen);
    }
    foreach (var itemss in mainList)
    {

        OrdersKitchen kitchen2 = new OrdersKitchen();
        kitchen2.ProductID = Convert.ToInt32(itemss.MainProductID);
        kitchen2.UserID = User.UserID;
        kitchen2.UserName = Util.User.FirstName;
        kitchen2.LastName = Util.User.LastName;
        kitchen2.BillID = bill.BillID;
        kitchen2.Quantity = Convert.ToInt32(0); //HARDCODE ZERO
        OrdersKitchen.Add(kitchen2);
    }
 }

mainList.Clear();
//forPrintKitchenOrders.Clear();
}

看到回复后，我阅读了@sachin的帖子，并编写了与他们相似的代码.这样好吗看来它现在正在运行，但是我不确定该解决方案还可以吗?

After I saw the replies, I read @sachin's post and wrote a code similar to theirs. Is this alright? It looks like it's working right now, but I am not sure is this solution ok?

foreach (var itemss in forPrintKitchenOrders)
{
    forPrintKitchenOrders.Add(new OrderTemp(itemss._articleCode,itemss._name,itemss._quantity,itemss._amount));
}

public class OrderTemp
{
        public string _articleCode;
        public string _name;
        public string _quantity;
        public double _amount;

        public OrderTemp(string articleCode, string name, string quantity, double amount)
        {
            _articleCode = amount;
            _name = name;
            _quantity = quantity;
            _amount = amount;
        }
}

推荐答案

您称为"副本列表"的集合实际上不是副本.

The collection that you are referring to as 'Copy List' is not actually a Copy.

集合中的元素是指与原始集合中相同的对象.

您将必须用以下代码替换foreach循环:

You will have to replace your copying foreach loop with something like this:

foreach (var item in forPrintKitchen)
{
    forPrintKitchenOrders.Add(item.Clone()); // The clone method should return a new Instance after copying properties from item.
}

Clone方法应创建new实例，并从要克隆的实例中复制每个属性，然后返回新创建的实例.

The Clone method should create new Instance and copy each of the properties from the instance being cloned and then return the newly created Instance.

基本上，您必须像这样在OrderTemp类中定义一个名为Clone(名称无关紧要)的方法:

Basically you'll have to define a method named Clone (name doesn't matter) in OrderTemp class like this:

public class OrderTemp
{
    /*  other members of the class */
    public OrderTemp Clone()
    {
        return new OrderTemp
        {
            property1 = this.property1;
            property2 = this.property2;
            /* and so on */
        };
    }
}

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