c# - 可以在迭代列表时修改它吗？

Question

我有以下内容：

foreach (var depthCard in depthCards)
{
    var card = InternalGetCard(db, depthCard.CardId);
    var set = InternalGetSet(db, (int)card.ParentSetId);
    var depthArray = InternalGetDepthArrayForCard(db, set.SetId);
    foreach (var cardToUpdate in set.Cards)
    {
        // do stuff
        SaveChanges(db);
        // since I already took care of it here, remove from depthCards
        depthCards.Remove(depthCardToUpdate);
    }
}

这不起作用，因为我正在循环中间修改集合。是否有某种类型的集合确实允许这种类型的访问？

我不想这样做ToList()，depthCards因为我已经拥有它们并且我想在迭代时修改该列表。这可能吗？

Answer 1

这是可能的，诀窍是向后迭代：

for (int i = depthCards.Count - 1; i >= 0; i--) {
  if (depthCards[i] == something) { // condition to remove element, if applicable
     depthCards.RemoveAt(i);
  }
}

Answer 2

for您可以使用-loop向后迭代

for (int i = depthCards.Count - 1; i >= 0; i--)
{
    depthCards.RemoveAt(i);
}

或者，如果您只想删除某个条件下的项目，请使用List.RemoveAll：

depthCardToUpdate.RemoveAll(dc => conditionHere);

Answer 3

You can create a custom enumerator that handles this for you. I did this once and it was a bit tricky but worked after some finesse.

See: http://www.codeproject.com/Articles/28963/Custom-Enumerators