Hash table

Question

What is hash table and what are their exact use?

Vulpes · Answer

A Hashtable is a collection of key/value pairs where the keys need to be unique but the values need not be. You can look up a value in the Hashtable using its key. A Hashtable (or its generic equivalent Dictionary ) is therefore suitable when you need keyed access to a collection. For example: Hashtable ht = new Hashtable(); ht.Add(Akash 1); ht.Add(Vulpes 2); // get value for Akash int value = (int)ht[Akash]; // 1 Notice that a Hashtable stores everything internally as type System.Object. When retrieving a value you therefore have to cast it to its actual type. This is unnecessary when using Dictionary which stores the keys and values using their actual types and doesn't require boxing/unboxing when the keys or values are value types (int double bool etc).

Akash Ahlawat · Answer

Thanks guys.

Jignesh Trivedi · Answer

hi A HashTable collection stores a (Key and Value) pair and uses the Key to hash and obtain the storage location. The Key is immutable and cann't have duplicate entries in the HashTable. it also provided a indexer. u can learn more from http://msdn.microsoft.com/en-us/library/7b3y50ay.aspx hope this help