Question

Is there such a thing as a thing that returns an IEnumerable<object> or IEnumerable<T> for each matching hash code in .Net 4? That is, I want something that just uses the GetHashCode() and ignores the equality operator.

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I thought I was barking up the wrong tree for a while after all these comments. But I found these guys. Granted it’s a .net 2 implementation… but at least a few other people thought a 1:n mapping using hash keys was a good idea. See the description for HashMap under http://recursionsw.com/Products/csharp.html

Answer 1

You could use the ToLookup<>. But I’m not sure it’s what you really want. An example

public class MyClass
{
    public int Num = (new Random()).Next(100);
}

var manyA = new List<MyClass>();

var groupedByHash = manyA.ToLookup(p => p.GetHashCode());

Now each group in groupedByHash will contain all the elements that share the same hashcode. You can consider them to be “equal” by your standard.