C# 从对象列表中删除对象
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C# Remove object from list of objects
提问by user9993
I have a list of objects and I am trying to remove a specific object in the list by first checking a property in the object.
我有一个对象列表，我试图通过首先检查对象中的属性来删除列表中的特定对象。
Originally I used a foreachbut then realised you can't use this while modifying a collection, so I decided to use a normal forbut then I'm not sure how to write code that does what I originally wrote.
最初我使用了 aforeach但后来意识到你不能在修改集合时使用它，所以我决定使用普通for但后来我不确定如何编写代码来完成我最初编写的代码。
How do I go about writing code to do what I originally had?
我该如何编写代码来完成我最初的工作？
Thanks
谢谢
Here's my code:
这是我的代码：
public void DeleteChunk(int ChunkID)
{
//foreach (Chunk i in ChunkList)
//{
// if (i.UniqueID == ChunkID)
// {
// ChunkList.Remove(i);
// }
//}
//This won't work because here i is just an integer so i.UniqueID won't exist.
for (int i = 0; i < ChunkList.Capacity; i++)
{
if (i.UniqueID == ChunkID)
{
ChunkList.Remove(i);
}
}
}
回答by Khan
You can simplify this with linq:
您可以使用 linq 简化此操作：
var item = ChunkList.SingleOrDefault(x => x.UniqueId == ChunkID);
if (item != null)
ChunkList.Remove(item);
You can also do the following, which will also work if there is more than one match:
您还可以执行以下操作，如果存在多个匹配项，这也将起作用：
ChunkList.RemoveAll(x => x.UniqueId == ChunkID);
回答by bland
You're removing and then incrementing, which means you'll be one ahead of yourself. Instead, remove in reverse so you never mess up your next item.
您正在删除然后递增，这意味着您将领先于自己。相反，反向删除，这样你就不会弄乱你的下一个项目。
for (int i = ChunkList.Count-1; i >=0; i--)
{
if (ChunkList[i].UniqueID == ChunkID)
{
ChunkList.RemoveAt(i);
}
}
回答by bland
One technique is to create a copy of the collection you want to modify, change the copy as needed, then replace the original collection with the copy at the end.
一种技术是创建要修改的集合的副本，根据需要更改副本，然后用最后的副本替换原始集合。
回答by dasblinkenlight
There are two problems with this code:
这段代码有两个问题：
回答by Moo-Juice
If ChunkListis List<Chunk>, you can use the RemoveAllmethod:
如果ChunkList是List<Chunk>，则可以使用以下RemoveAll方法：
ChunkList.RemoveAll(chunk => chunk.UniqueID == ChunkID);
回答by Raz Harush
You're checking i's UniqueIDwhile iis actually an integer. You should do something like that, if you want to stay with a forloop.
您正在检查i's UniqueIDwhilei实际上是一个整数。如果你想保持for循环，你应该做类似的事情。
for (int i = 0; i < ChunkList.Capacity; i++)
{
if (ChunkList[i].UniqueID == ChunkID)
{
ChunkList.Remove(i);
}
}
You can, and should, however, use linq:
但是，您可以并且应该使用 linq：
ChunkList.Remove(x => x.UniqueID == ChunkID);
回答by DGibbs
Originally I used a foreach but then realised you can't use this while modifying a collection
最初我使用了 foreach 但后来意识到你不能在修改集合时使用它
You can create a copy of the collection and iterate over that using ToList()to create to copy:
您可以创建集合的副本并使用ToList()create to copy 对其进行迭代：
foreach(Chunk chunk in ChunkList.ToList())
{
if (chunk.UniqueID == ChunkID)
{
ChunkList.Remove(chunk);
}
}
回答by Matthew Watson
Firstly, you are using Capacityinstead of Count.
首先，您使用的是Capacity代替Count.
Secondly, if you onlyneed to delete oneitem, then you can happily use a loop. You just need to ensure that you break out of the loop after deleting an item, like so:
其次，如果你只需要删除一项，那么你可以愉快地使用循环。您只需要确保在删除项目后跳出循环，如下所示：
int target = 4;
for (int i = 0; i < list.Count; ++i)
{
if (list[i].UniqueID == target)
{
list.RemoveAt(i);
break;
}
}
If you want to remove allitems from the list that match an ID, it becomes even easier because you can use List<T>.RemoveAll(Predicate<T> match)
如果您想从列表中删除与 ID 匹配的所有项目，则变得更加容易，因为您可以使用List<T>.RemoveAll(Predicate<T> match)
int target = 4;
list.RemoveAll(element => element.UniqueID == target);
回答by knguyen
You can use a while loop to delete item/items matching ChunkID. Here is my suggestion:
您可以使用 while 循环删除与 ChunkID 匹配的项目。这是我的建议：
public void DeleteChunk(int ChunkID)
{
int i = 0;
while (i < ChunkList.Count)
{
Chunk currentChunk = ChunkList[i];
if (currentChunk.UniqueID == ChunkID) {
ChunkList.RemoveAt(i);
}
else {
i++;
}
}
}
回答by knocte
Simplest solution without using LINQ:
不使用 LINQ 的最简单解决方案：
Chunk toRemove = null;
foreach (Chunk i in ChunkList)
{
if (i.UniqueID == ChunkID)
{
toRemove = i;
break;
}
}
if (toRemove != null) {
ChunkList.Remove(toRemove);
}
(If Chunk is a struct, then you can use Nullable<Chunk> to achieve this.)
（如果 Chunk 是一个结构体，那么您可以使用 Nullable<Chunk> 来实现这一点。）
