无法修改 Dictionary 的返回值，因为它不是变量

有这样的错误：无法修改 'System.Collections.Generic.Dictionary.this[string]' 的返回值，因为它不是变量。`

My code:

Dictionary<string, lim> urlsLimited = new Dictionary<string, lim>();
struct lim
{
    public int min;
    public int max;
}
void main ()
{
    ....
    foreach (KeyValuePair<string, lim> pair in urlsLimited)
    {
        string like = od.LikeDiscussions(pair.Key);
        if (like == "Like")
        {
            lock (locker)
            {
                urlsLimited[pair.Key].min++; // error

            }
        }
    }
    ....
}

如何迭代 urlsLimited[pair.Key].min++？

您需要将值分配给局部变量，执行增量，然后将其设置回字典。

foreach (KeyValuePair<string, lim> pair in urlsLimited)
{
    string like = od.LikeDiscussions(pair.Key);
    if (like == "Like")
    {
        lock (locker)
        {
            lim val = pair.Value;
            val.min++;
            urlsLimited[pair.Key] = val;
        }
    }
}

要获得更好的解释，请参阅 Jon Skeet 对相关问题的回答：https://stackoverflow.com/a/6255368/1149773 https://stackoverflow.com/a/6255368/1149773.