Question

我已定义Dictionary如下：

Dictionary<string, double> collection = new Dictionary<string, double>();

现在我想更新我的价值：

foreach (KeyValuePair<string, double> pair int collection)
{
    double val = 3.0;
    collection[pair.Value] = val; // Get an error
}

我的错误是无法从double转换为字符串。那是为什么？

Answer 1

您不能迭代Dictionary并更改内部值，因为它会破坏迭代器。

您需要复制该集合，并修改复制的版本...示例如下：

Dictionary<string, double> collection = new Dictionary<string, double>();
collection.Add("A", 1.0);
collection.Add("B", 2.0);

Dictionary<string, double> collection2 = new Dictionary<string, double>(collection);

foreach (KeyValuePair<string, double> pair in collection)
{
  double val = 3.0;              
  collection2.Remove(pair.Key);
  collection2.Add(pair.Key, val);
 }

Answer 2

试试这个

   Dictionary<string, double> Copycollection= new Dictionary<string, double>  (collections);
            foreach (KeyValuePair<string, double> pair in Copycollection)
             {
                double val = 3.0;
                collection[pair.Key] = val; 
            }

通过循环更新字典值字段

2 个答案: