asp.net-mvc - 如何克服此错误 :- Collection was modified; enumeration operation may not execute.“

Question

我有以下方法:-

public void AssignGroupRole(int id, int[] selectedGroups, int[] currentGroups)
        {
            var roleGroups = FindRole(id).Groups;
            var roleGroupsCopy = roleGroups;
            var securityRole = FindRole(id);
            foreach (var group in roleGroupsCopy)
            {
                if (currentGroups != null)
                {
                    for (int c = 0; c < currentGroups.Count(); c++)
                    {
                        if (group.GroupID == currentGroups[c])
                        {

                            securityRole.Groups.Remove(group);
                        }
                    }
                }
            }

但我收到错误消息“集合已修改；枚举操作可能无法执行。”在

foreach (var group in roleGroupsCopy)

关于如何克服此错误的建议？

Answer 1

您可以使用:

foreach (var group in roleGroupsCopy.ToList())

调用 ToList() 将其复制到您循环访问的临时列表。临时列表不会被修改。

另一种方法是使用:

securityRole.Groups.RemoveAll(g => g.GroupID == currentGroups[c]);