Working with Dictionaries

mtillett

I am not sure if I have missed something, but I am trying to figure out why you would ever use a Hashtable or a ListDictionary when you have a HybridDictionary.

ListDictionarys are for small lists, Hashtables are for large, but HybridDictionarys start as a ListDictionary and when the list is large enough they auto upgrade themselves to a HashTable.

Is there a performance issue or something because I cannot see why you would ever use the HashTable or ListDictionary when you have a HybridDictionary.

Many thanks,

bcairns

Hashtables have been around since the birth of .Net (longer if you talk about other languages).

Hashtable = dictionary of objects

ListDictionarys = an array good performance on small lists

HybridDictionarys = an advanced version of the ListDictionary, a class that upgrades the from a Array to a Dictionary object.

In sort most people will use a hashtable because it has been around forever.

That and most of the .net 1.0 developers dont know about the ListDictionarys and HybridDictionarys.

JDMurray

Hmmmm...it looks like Lists, ArrayLists, Hashtables, ListDictionarys, and HybridDictionarys would be a good first exam topic study thread for this forum.

mtillett

I did some followup testing counting the ticks passed during a lookup and found that listdictionarys are definitely faster with small lists and hashtables are faster for large lists. Adding a hybriddictionary has a performance hit and is without doubt the slowest of the three.

In my opinion, only use a hybriddictionary when you are truly unsure of the list size.