IDictionary How to get the removed item value while removing

I would like to know if it is possible to remove an IDictionary item by its key and in the same time get its actual value that has been removed?

IDictionary

something like:

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");



//We have just remove value1


out removed

null

default(T)

null

default(T)

2 Answers
2

Normal dictionaries don't have this functionality as an atomic operation but a ConcurrentDictionary<TKey,TValue> does.

ConcurrentDictionary<TKey,TValue>

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");



You could write an extension method for a normal dictionary to implement this but if you are concerned about it being atomic a ConcurrentDictionary is probably more correct for your use case.

You could write an extension method for this:

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;




This will attempt to get the value and if it exists, will remove it. Otherwise you should use a ConcurrentDictionary as the other answer said.

ConcurrentDictionary

value = default(TValue);

return dict.TryGetValue(key, out value) && dict.Remove(key);

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