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Thursday, March 15, 2012

Arraylist,Hash table,Sorted list and Dictionary C#.Net

In this article we will discuss about Arraylist, Hash table, Sorted list and Dictionary. Also you can check my last article on Delegates in C#.net.
Arraylist:
- This is one type of Array whose size can increase and decrease dynamically.

- Arraylist can hold items of different types.

- The base class is System.Collections.ArrrayList.

- An ArrayList uses an array internally and initializes its size with a default value called capacity. As the no of elements increases or decreases , it adjust the capacity of the array by making a new array and copying the old values into it.
ArrayList list = new ArrayList();

To add elements in ArrayList
list.add("Raju");
list.add("biju");

To remove the element from the arraylist
list.Remove("raju");
To remove the element at index 1
list.Remove(1);
To remove three elements starting at index 4
list.RemoveRange(4,3);

Hash table:

- Hash table provides a way of accessing the index using a user identified key value.

- It removes the index problem.

- It stores the items as key value pairs.Each item(value) in the hash table is uniquely identified by its key and its value as an object type.

- Mostly string class is used as the key in hash table but we can also use other class as key.

Hashtable myht = new Hashtable();
myht.Add("one","The");
myht.Add("two","quick");

Here 'two' and 'one' are the keys and 'The' and 'quick' are the values.

PrintKeysAndValues(myht);

To remove elements with the key "two"

myht.Remove("two");

Sorted list:
Simillar to Hash table, the difference is that the values are sorted by keys and acessible by key as well as by index.

SortedList mysl = new SortedList();
mysl.Add("one","The");
mysl.Add("two","quick");

Dictionary:
- A kind of collection that stores items in a key-value pair fashion.

- Each value in the collection is identified by its key.

- All the keys in the collection are unique and there cannot be more than one key with the same name.

- The most common types of dictionary in the system.collection name space are Hash table and the sorted list.

Also you can check Connected and Disconnected Architecture Ado.Net.




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