c# - 系统.InvalidOperationException : Collection was modified

Question

我在通过队列进行枚举时遇到以下异常:

System.InvalidOperationException: Collection was modified; enumeration operation may not execute

这里是代码摘录:

1:    private bool extractWriteActions(out List<WriteChannel> channelWrites)
2:    {
3:        channelWrites = new List<WriteChannel>();
4:        foreach (TpotAction action in tpotActionQueue)
5:        {
6:            if (action is WriteChannel)
7:            {
8:                channelWrites.Add((WriteChannel)action);
9:                lock(tpotActionQueue)
10:               {
11:                  action.Status = RecordStatus.Batched;
12:               }
13:           }
14:       }
15:       return (channelWrites.Count > 0);
16:   }

我想我理解这个问题 - 在 action.Status = RecordStatus.Batched 处更改哈希表，这会搞砸枚举器上的 MoveNext()。问题是，我该如何正确实现该“模式”？

Answer 1

我想我在 Collection 上使用 foreach 循环时遇到了类似的异常，我试图从 Collection 中删除项目(或者它可能是一个列表，我不记得了)。我最终通过使用 for 循环绕过了它。也许尝试以下操作:

for (int i=0; i<tpotActionQueue.Count(); i++)
{
    TpotAction action = tpotActionQueue.Dequeue();
    if (action is WriteChannel)
    {
        channelWrites.Add((WriteChannel)action);
        lock(tpotActionQueue)
        {
            action.Status = RecordStatus.Batched;
        }
    }
}