Hashtable v.s. Dictionary

Question

Hello everyone, Any guidelines about when to use Hashtable and when to use Dictionary? I always use Dictionary. :-) thanks in advance, George

Niradhip Chakraborty · Answer

Dictionary is a hashtable, SortedDictionary is a dictionary implemented as a red-black tree and maintains an order. SortedList appears to be implemented as a list, using a straight sequential algorithm to locate keys. Each one has different uses, obviously. Dictionary has no order, so it is appropriate in any circumstance where order is irrelevent. SortedList would have linear search time, as the last key in the list will require comparisions to every preceding key, I wouldn't use it for alot of items if you will be accessing them randomly. I suspect it would be a good choice if you will access the items in sequence however. SortedDictionary uses a tree and has a an O(log n) retrieval time, use it when you will be doing random(key by indexer) retrevials with a fair number of items, I suspect it won't be as efficent as SortedList when accessing items in sequence, but I've run no tests to prove that. Check Out the following article: http://arcanecode.wordpress.com/2007/03/05/dictionaries-in-c-the-hashtable/

Satyapriya Nayak · Answer

Hi George, Please refer the below links http://www.c-sharpcorner.com/UploadFile/pradeep.tiwari/PradeepTiwariHashtable11072006072247AM/PradeepTiwariHashtable.aspx http://www.c-sharpcorner.com/UploadFile/mahesh/Hashtable11082005171748PM/Hashtable.aspx http://www.c-sharpcorner.com/uploadfile/husseinahmed/dictionary-class-in-C-Sharp/default.aspx http://www.c-sharpcorner.com/UploadFile/mahesh/dictionary-in-C-Sharp/ Thanks

Ta As · Answer

Here is the link http://www.tanvtech.com/Userrequestpage.aspx?Id=2

George George · Answer

Thanks James, I read your great reply and your referred link. 3 more comments, 1. you mentioned "sequential algorithm"? What does it mean? Could you provide more description or refer a link please? 2. You mentioned "a fair number of items" -- do you mean a big number of a small number? Sorry, my English is not good. :-) 3. In your referred link, it is mentioned -- "The most basic type of Dictionary is the Hashtable. The hashtable has the basic functionality for putting entries into the dictionary collection, getting a value based on a key, looping through them, and updating or removing them.". But I still can not find the additional functions provided by Dictionary, which Hashtable does not have. Could you help to clarify please? regards, George

George George · Answer

Thanks Jan, Great link! I like to learn new things like TryGetValue from you referred material. Another question, I heard we should always use Dictinoary other than Hashtable because Hashtable is depreciated since .Net 2.0. Is that correct? regards, George

Jan Montano · Answer

Just read this one on a forum: Dictionary vs HashTable

Hashtable v.s. Dictionary

Answers (6)