IDictionary如何在删除时获取已删除的项值

Question

我想知道是否可以IDictionary通过其键删除项目,同时获取已删除的实际值？

例

就像是:

Dictionary<string,string> myDic = new Dictionary<string,string>();
myDic["key1"] = "value1";

string removed;
if (nameValues.Remove("key1", out removed)) //No overload for this...
{
    Console.WriteLine($"We have just remove {removed}");
}

产量

//We have just remove value1

Answer 1

普通词典没有像原子操作那样的功能,但ConcurrentDictionary<TKey,TValue> 确实如此.

ConcurrentDictionary<string,string> myDic = new ConcurrentDictionary<string,string>();
myDic["key1"] = "value1";

string removed;
if (myDic.TryRemove("key1", out removed))
{
    Console.WriteLine($"We have just remove {removed}");
}

你可以编写一个普通字典的扩展方法来实现它,但是如果你担心它是原子的,那么ConcurrentDictionary可能对你的用例更正确.

Answer 2

您可以为此编写扩展方法:

public static class DictionaryExtensions
{
    public static bool TryRemove<TKey, TValue>(this IDictionary<TKey, TValue> dict, TKey key, out TValue value)
    {
        if (dict.TryGetValue(key, out value))
            return dict.Remove(key);
        else
            return false;
    }
}

这将尝试获取值,如果存在,将删除它.否则你应该用ConcurrentDictionary另一个答案说.