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Asked: 2026-06-12T19:02:13+00:00

I’m trying to improve on some code that was written a while back. the

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I’m trying to improve on some code that was written a while back. the function is quite important to the core functionality of the system so I am cautious about a drastic overhaul.

I am using a dictionary to hold objects 

Dictionary<Node, int> dConnections

The object Node is in itself a complex object containing many attributes and some lists.
This Dictionary could get quite large holding around 100 or more entries.

Currently the dictionary is being checked if it contains a node like 

dConnections.ContainsKey(Node)

So I am presuming that (to check if this node is in the dictionary) the dictionary will have to check if the whole node and its attributes match a node in the dictionary (it will keep on iterating through the dictionary until it finds a match) and this will have a major impact on performance?

Would I be better off not using an object in the dictionary and rather use object id.

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1 Answer

  1. Editorial Team

    The .NET dictionary is an hashtable in the Inside. It means that if Node doesn’t overrides the GetHashCode and Equals methods, when you call ContainsKey, it will match against:

    Disclaimer: It’s a summary. Things are a little more complicated. Please don’t call me name because I oversimplified.

    1. a partition of the hashcode of the ref address of the Node object. The number of partitions dépends upon the number of buckets of the hashtable (depending on the total number of keys in the dictionnary)
    2. the exact ref address if more than one Node is in the same bucket.

    This algorithm is very efficient. When you say that you have 100 or more entries in the dictionary, it’s not “a lot”. It’s a few.

    It means also that the content of the Node object has nothing to do with the way a ContainsKey will match. It will match against the exact same reference, and only against this reference.

    If you implement GetHashCode and Equals yourself, be aware that these method return values shouldn’t change when the instance property change (be immutable). Otherwise you could well get keys in the wrong bucket, and therefore completely unreachable (without enumerating the whole dictionary).

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