What is the difference between dictionary and hashtable in c

Dictionary throws an exception if we try to find a key which does not exist. Data retrieval is slower than dictionary because of boxing-unboxing. Data retrieval is faster than Hashtable. Related Articles. How to sort the generic SortedList in the descending order? Difference between Array and ArrayList. Share Tweet Share Whatsapp. Generic; using System. Collections ; using System.

Add 1, "one" ; numbers. Add 2, "two" ; numbers. Add 3, "three" ; numbers. Add 4, "four" ; numbers. Show num. Add 1,"one" ; dictionary. Add 2,"two" ; dictionary. Add 3,"three" ; dictionary. A dictionary uses a key to reference the value directly inside of an associative array. A hash is more often described as a hash table which uses a hash function to calculate the position in memory or more easily an array where the value will be.

The hash will take the KEY as input and give a value as output. Then plug that value into the memory or array index. I guess one is direct while the other isn't. Hash functions may not be perfect either and may sometimes provide an index referencing the wrong value.

But that can be corrected. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group.

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Asked 10 years, 10 months ago. Add a comment. Active Oldest Votes. Gabe Marc Gravell Marc Gravell k gold badges silver badges bronze badges. But Dictionary's instance methods aren't thread-safe, unlike the Hashtable — t3mujin.

Lets give an example that would explain the difference between hashtable and dictionary. Add 2. ToString ; lblDisplay2.

ToString ; lblDisplay3. ToString ; lblDisplay4. Add "cat", 2 ; dictionary. Add "dog", 1 ; dictionary. Add "llama", 0 ; dictionary. Pritom Nandy Pritom Nandy 1, 9 9 silver badges 5 5 bronze badges. As a note You have to use a DictionaryEntry as your variable, which can then provide key and value objects.

Superb answer,Also you can use DictionaryEntry for enumerate over Hashtable. Key, entry. Rohit Gupta Rohit Gupta 1 1 gold badge 5 5 silver badges 15 15 bronze badges.

Frans Bouma Frans Bouma 8, 1 1 gold badge 25 25 silver badges 27 27 bronze badges. For multiple values per key: in. Unfortunately the default concrete implementation is immutable, but it is easy to re-implement or add to your MultiValueDictionary. Good tip indeed, I had forgotten about that interface.

I looked at the implementation in the BCL but it's indeed immutable so pretty much useless for every-day multi-value usage ;. I'll add the interface. Republished code: weblogs. Which makes it harder to use the dictionary as it requires explicit type specfication.