C# Collections - c# - c# tutorial - c# net
What is C# Collections ?
- In C#, collection represents group of objects. By the help of collections, we can perform various operations on objects such as
- store object
- update object
- delete object
- retrieve object
- search object, and
- sort object
- In sort, all the data structure work can be performed by C# collections.
- We can store objects in array or collection.
- Collection has advantage over array.
- Array has size limit but objects stored in collection can grow or shrink dynamically.
- The System.Collections namespace includes following non-generic collections.
|ArrayList||ArrayList stores objects of any type like an array. However, there is no need to specify the size of the ArrayList like with an array as it grows automatically.|
|SortedList||SortedList stores key and value pairs. It automatically arranges elements in ascending order of key by default. C# includes both, generic and non-generic SortedList collection.|
|Stack||Stack stores the values in LIFO style (Last In First Out). It provides a Push() method to add a value and Pop() & Peek() methods to retrieve values. C# includes both, generic and non-generic Stack.|
|Queue||Queue stores the values in FIFO style (First In First Out). It keeps the order in which the values were added. It provides an Enqueue() method to add values and a Dequeue() method to retrieve values from the collection. C# includes generic and non-generic Queue.|
|Hashtable||Hashtable stores key and value pairs. It retrieves the values by comparing the hash value of the keys.|
|BitArray||BitArray manages a compact array of bit values, which are represented as Booleans, where true indicates that the bit is on (1) and false indicates the bit is off (0).|
Types of Collections in C#:
- There are 3 ways to work with collections. The three namespaces are given below:
- System.Collections.Generic classes
- System.Collections classes (Now deprecated)
- System.Collections.Concurrent classes
- The System.Collections.Generic namespace has following classes:
- These classes are legacy. It is suggested now to use System.Collections.Generic classes. The System.Collections namespace has following classes:
- The System.Collections.Concurrent namespace provides classes for thread-safe operations.
- Now multiple threads will not create problem for accessing the collection items.
- The System.Collections.Concurrent namespace has following classes:
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C# examples - Output :
- The following example removes an element from the collection by specifying the object to remove.
C# examples - Output :
- The following example removes elements from a generic list. Instead of a foreach statement, a for statement that iterates in descending order is used.
- This is because the RemoveAt method causes elements after a removed element to have a lower index value.