Hashtable

Description

Hashtable collection contains a group of elements of key/value pairs stored at respective indexes (Full Path: System.Collections.Hashtable).

Hashtable referenceVariable = new Hashtable();

• Process of adding an element:

  1. Generate index based on the key (Ex: `index = hash_code % size_of_hashtable$).
  2. Add the element (key and value) next to the linked list at the generated index.

• GetHashCode method of the key value will be used in the index calculation process

• When we want to use the objs of our custom class as the key inside a hashtable, we should implement the GetHashCode method of that class
• Elements with the same calculated index will be stored in the same index with the linked list data structure
• Each time, when the size of hashtable changes, all the exists indexes will be calculated automatically
• Hashtable will return System.Object instance, because we can store any type of data in Hashtables.
• After retrieving data from hashtable (with [TKey] or foreach loop), we should convert the result.
• Hashtable O(1) is faster than SortedList O(log n) in retrieving data
• Both Hashtable and SortedList have cost in data insert

Example:

Hashtable employees = new Hashtable()
{
    { 102, "Smith" },
    { 105, "James" },
    { 103, "Allen" },
    { 101, "Scott" },
    { 104, "Jones" },
    { "hello", 10.934 }
};

foreach (DictionaryEntry item in employees) {
    Console.WriteLine(item.Key + ", " + item.Value);
}

Features

Overview