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,

Hash table

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