Get original value from HashSet

Question

UPDATE: Starting with .Net 4.7.2, HashSet.TryGetValue - docs is available.
HashSet.TryGetValue - SO post

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I have a problem with HashSet because it does not provide any method similar to TryGetValue known from Dictionary. And I need such method -- passing element to find in the set, and set returning element from its collection (when found).

Sidenote -- "why do you need element from the set, you already have that element?". No, I don't, equality and identity are two different things.

HashSet is not sealed but all its fields are private, so deriving from it is pointless. I cannot use Dictionary instead because I need SetEquals method. I was thinking about grabbing a source for HashSet and adding desired method, but the license is not truly open source (I can look, but I cannot distribute/modify). I could use reflection but the arrays in HashSet are not readonly meaning I cannot bind to those fields once per instance lifetime.

And I don't want to use full blown library for just single class.

So far I am stuck with LINQ SingleOrDefault. So the question is how fix this -- have HashSet with TryGetValue?

Answer 1

Probably you should switch from a HashSet to a SortedSet

There is a simple TryGetValue() for a SortedSet:

public bool TryGetValue(ref T element)
{
    var foundSet = sortedSet.GetViewBetween(element, element);
    if(foundSet.Count == 1)
    {
        element = foundSet.First();
        return true;
    }
    return false;       
}

when called, the element needs just all properties set which are used in the Comparer. It returns the element found in the Set.