如何仅在按值过滤时检索键

Question

ConcurrentDictionary<int, int> dic = new ConcurrentDictionary<int, int>();
dic.AddOrUpdate(1, 2, (s, i) => 0);
dic.AddOrUpdate(2, 3, (s, i) => 0);
dic.AddOrUpdate(3, 1, (s, i) => 0);
dic.AddOrUpdate(4, 7, (s, i) => 0);

我只想 select 个值大于 5 的键。我该怎么做？

Answer 1

只是 select 个条目，根据值进行过滤，然后投射到键：

var keys = dic.Where(entry => entry.Value > 5)
              .Select(entry => entry.Key);

请注意，此方法适用于任何 IDictionary<,> - 您拥有 ConcurrentDictionary<,> 的事实与此无关。

如何仅在按值过滤时检索键

how to retrieve keys only when filter by value

c#

.net-4.0

concurrentdictionary