System.Collections Namespace

Types

• ICollection
• IDictionary
• IEnumerable
• IEnumerator
• IList
• IObjectCollection
• IObjectDictionary
• IObjectList

Classes

• ArrayList
• CaseInsensitiveComparer
• CaseInsensitiveHashCodeProvider
• CollectionBase
• DictionaryBase
• Hashtable
• Queue
• ReadOnlyCollectionBase
• SortedList
• Stack

Interfaces

The System.Collections namespace defines several fundamental interfaces for collections:

• IEnumerable: Supports iteration over a generic collection. Provides a single method, GetEnumerator, which returns an enumerator for the collection.
• ICollection: Represents a group of objects of the same type. Inherits from IEnumerable.
• IDictionary: Represents a collection of key/value pairs. Inherits from ICollection.
• IList: Represents a non-generic collection of objects that can be individually accessed by index. Inherits from ICollection.
• IEnumerator: Supports a simple iteration over a collection.

Classes

This namespace also provides several concrete classes that implement these interfaces, offering common collection functionalities:

ArrayList

Implements a dynamic array of objects. It can grow or shrink as needed.

public class ArrayList : IList, ICollection, IEnumerable

Hashtable

Implements a collection of key-value pairs that are organized based on the hash code of the keys. Offers efficient lookups.

public class Hashtable : IDictionary, ICollection, IEnumerable

Queue

Represents a first-in, first-out (FIFO) collection of objects.

public class Queue : ICollection, IEnumerable

Stack

Represents a last-in, first-out (LIFO) collection of objects.

public class Stack : ICollection, IEnumerable

SortedList

Implements a collection that maintains a sorted list of elements, where each element is a key/value pair. Keys are sorted and can be accessed by index.

public class SortedList : IDictionary, ICollection, IEnumerable

CollectionBase

Provides a base class for creating custom collection classes. It simplifies implementing the IList and ICollection interfaces.

public abstract class CollectionBase : IList, ICollection, IEnumerable

DictionaryBase

Provides a base class for creating custom dictionary collection classes. It simplifies implementing the IDictionary and ICollection interfaces.

public abstract class DictionaryBase : IDictionary, ICollection, IEnumerable

ReadOnlyCollectionBase

Provides a base class for custom read-only collection classes. Objects in a read-only collection cannot be modified.

public abstract class ReadOnlyCollectionBase : ICollection, IEnumerable

CaseInsensitiveComparer

Compares two objects for inequality using case-insensitive string comparison.

public class CaseInsensitiveComparer : IComparer

CaseInsensitiveHashCodeProvider

Provides a hash code implementation that is insensitive to case for string keys.

public class CaseInsensitiveHashCodeProvider : IHashCodeProvider