1. Collections

2. Collections The .NET Framework provides specialized classes for data storage and retrieval. These classes provide support for stacks, queues, lists, and hash tables. Most collection classes implement the same interfaces, and these interfaces may be inherited to create new collection classes that fit more specialized data storage needs.

3. Collections A collection is an object that simply allows you to group other objects. When choosing the way you want to group your objects, you first have to think about what you want to do with your objects. The .NET Framework provides specialized classes for data storage and retrieval. These classes provide support for Stacks, Queues, Lists, and Hash Tables.

4. Collection Classes have the following properties Collection classes are defined as part of the System.Collections or System.Collections.Generic namespace. Most collection classes derive from the interfaces ICollection, IComparer, IEnumerable, IList, IDictionary, and IDictionaryEnumerator and their generic equivalents. Using generic collection classes provides increased type-safety and in some cases can provide better performance, especially when storing value types.

5. There are some pre-defined classes in .Net class library which have implemented the concept of collection ArrayList Class HashTable Class Queue Class Stack Class SortedList Class A custom collection class can be created by implementing ICollection interface.

6. Creating a LIST For dynamic lists, the .NET Framework offers the generic class List. This class implements the IList, Icollection, IEnumerable, Ilist,Icollection, and Ienmerable interfaces. EX: public class Racer:Icomparable,IFormattable {//} We can create a list for above class using List class Ex: var racers =new List([params]);

7. Creating a List Adding Elements Racers.Add(new Racer([/*values*/]); Ex: Racer.Add(new Racer(24,Raghu,Veer,India,54)); With AddRange() method we can add multiple elements to the collection. Inserting Elements Recars.Insert(3,new Racer(/*values*/)); Removing elements You can remove elements from list also. Recers.RemoveAt(3);

8. Array Class One of the most basic collection classes. Its not really a collection class, due to its limitations and its not even located in the System.Collections namespace, but in the System namespace. It is strongly typed and can be compared to an array. It has a fixed size. Arrays can have multiple dimensions. You can access an item of an array by its index.

9. Queue Class Queues are useful for storing messages in the order they were received for sequential processing. Queues maintains FIFO (first in first out) system. With the Queue class in .NET you can create weakly typed collections that are ordered by the order they are added to the collection. Queue accepts a null reference as a valid value and allows duplicate elements.

10. This class implements a queue as a circular array. Objects stored in a Queue are inserted at one end and removed from the other. The capacity of a Queue is the number of elements the Queue can hold. As elements are added to a Queue, the capacity is automatically increased as required through reallocation. The capacity can be decreased by calling TrimToSize.

11. Methods in Queue Class Clear GetHashCode Clone GetType Contains Peek CopyTo ReferenceEquals Dequeue Synchronized Enqueue ToArray Equals ToString GetEnumerator TrimToSize

12. Stack Class Stack is implemented as a circular buffer. Stack follows LIFO (last in first out ) system. The Stack class is a weakly typed collection. Push method allows you to add items to the Stack. Peek method just gets the last object of the Stack. Pop method also get the last object and then removes that item from the Stack.

13. The capacity of a Stack is the number of elements the Stack can hold. As elements are added to a Stack, the capacity is automatically increased as required through reallocation. Stack accepts a null reference as a valid value and allows duplicate elements.

14. Methods in Stack Clear GetType Clone Peek Contains Pop CopyTo Push Equals ReferenceEquals GetEnumerator Synchronized GetHashCode ToArray ToString

15. LinkedList LinkedList is a general-purpose linked list. It supports enumerators and implements the ICollection interface, consistent with other collection classes in the .NET Framework. Each node in a LinkedList object is of the type LinkedListNode. Because the LinkedList is doubly linked, each node points forward to the Next node and backward to the Previous node. If the LinkedList is empty, the First and Last properties contain a null reference

16. SortedList A combination of the Array and the Hashtable. Access items in a SortedList by the index (like the Array), or by the key (like the Hashtable) Its sorted based on the key object. The index sequence is based on the sort sequence. A SortedList is generally slower than the Hashtable, due to the sorting. Weakly typed.

17. SortedList A SortedList object internally maintains two arrays to store the elements of the list; that is, one array for the keys and another array for the associated values. Each element is a key/value pair that can be accessed as a DictionaryEntry object. A key cannot be a null reference, but a value can be. The capacity of a SortedList object is the number of elements the SortedList can hold. As elements are added to a SortedList, the capacity is automatically increased as required through reallocation.

18. SortedList Class Methods GetKeyList Add GetType Clear GetValueList Clone IndexOfKey Contains IndexOfValue ContainsKey ReferenceEquals ContainsValue Remove CopyTo RemoveAt Equals SetByIndex GetByIndex Synchronized GetEnumerator ToString GetHashCode TrimToSize GetKey

19. HashTable Class Represents a collection of key/value pairs that are organized based on the hash code of the key. A weakly typed collection of key-value pairs. Lets you quickly get an object out of the collection by using its key. Access items in your weakly typed collection, based on a key, not on an index.

20. HashTable Class Each element is a key/value pair stored in a DictionaryEntry object. A key cannot be a null reference, but a value can be. Key objects must be immutable as long as they are used as keys in the Hashtable. When an element is added to the Hashtable, the element is placed into a bucket based on the hash code of the key.

21. Hashtable Class Methods Add GetEnumerator Clear GetHashCode Clone GetObjectData Contains GetType ContainsKey OnDeserialization ContainsValue ReferenceEquals CopyTo Remove Equals Synchronized ToString

22. DICTIONARIES Dictionaries represent a sophisticated data structure that allows you to access an element based on a key. Dictionaries are also known as hash tables or maps. .NET framework offers several dictionary classes. The main class you can use is Dictionary.

23. BIT ARRAYS If you need to deal with a number of bits, you can use the class BitArray and the struct BitVector32. BitArray is reference type that contains an array of ints, where for every 32 bits a new integer is used. BitVector32 If you know the number of bits you need in advance, you can use the BitVector32 structure instead of BitArray.