What is Collections in c#.net?

Question

What is Collections in c#.net? Please tell me with Example.

Satyapriya Nayak · Answer

Hi Magesh Introduction C# provides a rich set of collection classes they are ArrayList HashTable SortedList BitArray Queue Stack Collection classes are normally used to hold collections of values or objects in memory. In collection classes elements are inserted using either the Add or Insert method and deleted using the RemoveAt method. Finally collections can be iterated over using the foreach statement. The System.Collections namespace contains interfaces and classes that define various collections of objects such as lists queues bit arrays hash tables and dictionaries. ArrayList: Implements the IList interface using an array whose size is dynamically increased as required. Elements in this collection can be accessed using an integer index. Indexes in this collection are zero-based. Using multidimensional arrays as elements in an ArrayList collection is not supported. ArrayList ar = new ArrayList(); ar.Add( Code ); ar.Add( myne ); ar.Add( welcomes ); ar.Add( you ); for ( int i = 0; i Console.Write(ar[i].ToString() +   ); Console.WriteLine(); HashTable: Represents a collection of key/value pairs that are organized based on the hash code of the key. Each element is a key/value pair stored in a DictionaryEntry object. A key cannot be null but a value can be. When an element is added to the Hashtable the element is placed into a bucket based on the hash code of the key. Subsequent lookups of the key use the hash code of the key to search in only one particular bucket thus substantially reducing the number of key comparisons required to find an element. Hashtable ht = new Hashtable(); ht.Add( WebSite  http://www.codemyne.net ); ht.Add( Category  Tutorials ); // the elements are retrieved as KeyValuePair objects. Console.WriteLine(); foreach (DictionaryEntry de in ht) { Console.WriteLine( Key = {0} Value = {1}  de.Key de.Value); } // To get the values alone use the Values property. ICollection valueColl = ht.Values; // The elements of the ValueCollection are strongly typed // with the type that was specified for hash table values. Console.WriteLine(); foreach ( string s in valueColl) { Console.WriteLine( Value = {0}  s); } // To get the keys alone use the Keys property. ICollection keyColl = ht.Keys; // The elements of the KeyCollection are strongly typed // with the type that was specified for hash table keys. Console.WriteLine(); foreach ( string s in keyColl) { Console.WriteLine( Key = {0}  s); } //to remove a key/value pair Remove method is used ht.Remove( Category ); SortedList: The SortedList contains items in key/value pairs. A SortedList automatically sort the items in alphabetic or numeric order. A SortedList can be sized to its final size with the TrimToSize() method. A SortedList does not allow duplicate keys. Operations on a SortedList object tend to be slower than operations on a Hashtable object because of the sorting. SortedList slCountries = new SortedList(); slCountries.Add( I  India ); slCountries.Add( U  USA ); slCountries.Add( F  France ); slCountries.Add( J  Japan ); Console.WriteLine( 	-KEY-	-VALUE- ); for ( int i = 0; i { Console.WriteLine( 	{0}:	{1}  slCountries.GetKey(i) slCountries.GetByIndex(i)); } Console.WriteLine(); BitArray: Manages an 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). The size of a BitArray is controlled by the client. Elements in this collection can be accessed using an integer index. Indexes in this collection are zero-based. BitArray ba = new BitArray(5); ba[0] = true ; ba[1] = false ; ba[2] = true ; for ( int i = 0; i Console.WriteLine(ba[i].ToString()); IEnumerator ie; ie = ba.GetEnumerator(); while (ie.MoveNext()) Console.WriteLine(ie.Current.ToString()); Queue: Represents a first-in first-out (FIFO) collection of objects. Queues are useful for storing messages in the order they were received for sequential processing. 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. Queue accepts null as a valid value and allows duplicate elements. Queue q = new Queue(); q.Enqueue( data 1 ); q.Enqueue( data 2 ); q.Enqueue( data 3 ); foreach (Object var in q) Console.WriteLine(var.ToString()); IEnumerator ie; ie = q.GetEnumerator(); while (ie.MoveNext()) Console.WriteLine(ie.Current.ToString()); Stack: Represents a simple last-in-first-out (LIFO) non-generic collection of objects. Stack is implemented as a circular buffer. 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. // Creates and initializes a new Stack. Stack st = new Stack(); st.Push( Hello ); st.Push( World ); st.Push( ! ); foreach ( object var in st) Console.WriteLine(var.ToString()); // using IEnumerator IEnumerator ie; ie = st.GetEnumerator(); while (ie.MoveNext()) Console.WriteLine(ie.Current.ToString()); Console.Read(); Please refer the below links http://www.codemyne.net/%28S%28zwaehuenlz4iprygrl0xwjft%29%29/articles/Creating-Collections-in-CSharp.aspx?visitid=40&type=2 http://www.codeproject.com/Articles/31640/Basics-of-NET-Collections-in-C http://www.c-sharpcorner.com/uploadfile/skumaar_mca/collections-in-C-Sharp-arraylist-and-arrays/default.aspx http://msdn.microsoft.com/en-us/library/ybcx56wz%28v=vs.80%29.aspx Thanks

Senthilkumar · Answer

The System.Collections namespaces contain types that define various standard specialized and generic collection objects. ArrayList Bitarray Comparer HashTable Queue Stack SortedList LinkedList and etc.. It has several interfaces: IEnumerable IEnumerator ICollection IList IDictionary You can get more infomation on: http://msdn.microsoft.com/en-us/library/system.collections.aspx Examples: http://aspalliance.com/854_Working_with_Collections_in_C http://www.codeguru.com/csharp/csharp/cs_misc/sampleprograms/article.php/c4265/A-Collection-of-C-Net-Sample-Programs.htm http://msdn.microsoft.com/en-us/library/aa288257(v=vs.71).aspx

Rafnas T P · Answer

hi magesh I have already an aricle written for this Collection Please see below link it may help you to understand collections http://www.c-sharpcorner.com/article/collections-in-net/ http://www.c-sharpcorner.com/article/overview-of-list-collection-class-in-c-sharp/

Pramod Gupta · Answer

What is Collections in C# Collections is a group of objects. The .NET Framework contains a large number of interfaces and classes that define and implement various types of collections. please visit below link for full blog. http://www.csharplearningsquare.com/2017/04/collections-csharp-mvc-angular.html