替换对象列表中的对象

Question

在C#中,如果我有List<T>,我有类型的对象T,我怎么能在替换特定项目List<T>类型的对象T？

这是我尝试过的:

List<CustomListItem> customListItems = new List<CustomListItem>();
CustomListItem customListItem1 = new CustomListItem() { name = "Item 1", date = DateTime.MinValue};
CustomListItem customListItem2 = new CustomListItem() { name = "Item 2", date = DateTime.MinValue };
CustomListItem customListItem3 = new CustomListItem() { name = "Item 3", date = DateTime.MinValue };

customListItems.Add(customListItem1);
customListItems.Add(customListItem2);
customListItems.Add(customListItem3);

CustomListItem newCustomListItem = new CustomListItem() { name = "Item 4", date = DateTime.Now };

customListItem2 = customListItems.Where(i=> i.name == "Item 2").First();
customListItem2 = newCustomListItem;

在上面的代码中,我想替换customListItem2为newCustomListItem.

我是否必须删除列表中的项目,然后插入新项目？我可以不做一个简单的任务customListItem2 = newCustomListItem吗？

用另一个项目替换列表中项目的最有效方法是什么？

提前致谢

Answer 1

您必须替换项目,而不是值customListItem2.只需更换以下内容

customListItem2 = customListItems.Where(i=> i.name == "Item 2").First();
customListItem2 = newCustomListItem;

有了这个:

customListItem2 = customListItems.Where(i=> i.name == "Item 2").First();
var index = customListItems.IndexOf(customListItem2);

if(index != -1)
    customListItems[index] = newCustomListItem;

编辑:

正如Roman R.在评论中所说,你可以用.Where(predicate).First()一个简单的替换 First(predicate):

customListItem2 = customListItems.First(i=> i.name == "Item 2");

Answer 2

var customListItems = new List<CustomListItem>();
var customListItem1 = new CustomListItem() { name = "Item 1", date = DateTime.MinValue };
var customListItem2 = new CustomListItem() { name = "Item 2", date = DateTime.MinValue };
var customListItem3 = new CustomListItem() { name = "Item 3", date = DateTime.MinValue };

customListItems.Add(customListItem1);
customListItems.Add(customListItem2);
customListItems.Add(customListItem3);

var newCustomListItem = new CustomListItem() { name = "Item 4", date = DateTime.Now };

customListItems[customListItems.FindIndex(x => x.name == "Item 2")] = newCustomListItem;

要么

public static class ListExtensions
{
    public static void Replace<T>(this List<T> list, Predicate<T> oldItemSelector , T newItem)
    {
        //check for different situations here and throw exception
        //if list contains multiple items that match the predicate
        //or check for nullability of list and etc ...
        var oldItemIndex = list.FindIndex(oldItemSelector);
        list[oldItemIndex] = newItem;
    }
}

然后

customListItems.Replace(x => x.name == "Item 2", newCustomListItem);