ICollection<T> Interface

Definition

generic <typename T>public interface class ICollection : System::Collections::Generic::IEnumerable<T>

public interface ICollection<T> : System.Collections.Generic.IEnumerable<T>

type ICollection<'T> = interface    interface seq<'T>    interface IEnumerable

Public Interface ICollection(Of T)Implements IEnumerable(Of T)

Type Parameters

Derived

Microsoft.Extensions.AI.AdditionalPropertiesDictionary<TValue>

Microsoft.Extensions.AI.AIFunctionArguments

Microsoft.Extensions.AI.GeneratedEmbeddings<TEmbedding>

Microsoft.Extensions.DependencyInjection.IServiceCollection

Microsoft.Extensions.DependencyInjection.ServiceCollection

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Implements

IEnumerable<T>IEnumerable

Examples

The following example implements theICollection<T> interface to create a collection of customBox objects namedBoxCollection. EachBox has height, length, and width properties, which are used to define equality. Equality can be defined as all dimensions being the same or the volume being the same. TheBox class implements theIEquatable<T> interface to define the default equality as the dimensions being the same.

TheBoxCollection class implements theContains method to use the default equality to determine whether aBox is in the collection. This method is used by theAdd method so that eachBox added to the collection has a unique set of dimensions. TheBoxCollection class also provides an overload of theContains method that takes a specifiedEqualityComparer<T> object, such asBoxSameDimensions andBoxSameVol classes in the example.

This example also implements anIEnumerator<T> interface for theBoxCollection class so that the collection can be enumerated.

using System;using System.Collections;using System.Collections.Generic;class Program{    static void Main(string[] args)    {        BoxCollection bxList = new BoxCollection();        bxList.Add(new Box(10, 4, 6));        bxList.Add(new Box(4, 6, 10));        bxList.Add(new Box(6, 10, 4));        bxList.Add(new Box(12, 8, 10));        // Same dimensions. Cannot be added:        bxList.Add(new Box(10, 4, 6));        // Test the Remove method.        Display(bxList);        Console.WriteLine("Removing 6x10x4");        bxList.Remove(new Box(6, 10, 4));        Display(bxList);        // Test the Contains method.        Box BoxCheck = new Box(8, 12, 10);        Console.WriteLine("Contains {0}x{1}x{2} by dimensions: {3}",            BoxCheck.Height.ToString(), BoxCheck.Length.ToString(),            BoxCheck.Width.ToString(), bxList.Contains(BoxCheck).ToString());        // Test the Contains method overload with a specified equality comparer.        Console.WriteLine("Contains {0}x{1}x{2} by volume: {3}",            BoxCheck.Height.ToString(), BoxCheck.Length.ToString(),            BoxCheck.Width.ToString(), bxList.Contains(BoxCheck,            new BoxSameVol()).ToString());    }    public static void Display(BoxCollection bxList)    {        Console.WriteLine("\nHeight\tLength\tWidth\tHash Code");        foreach (Box bx in bxList)        {            Console.WriteLine("{0}\t{1}\t{2}\t{3}",                bx.Height.ToString(), bx.Length.ToString(),                bx.Width.ToString(), bx.GetHashCode().ToString());        }        // Results by manipulating the enumerator directly:        //IEnumerator enumerator = bxList.GetEnumerator();        //Console.WriteLine("\nHeight\tLength\tWidth\tHash Code");        //while (enumerator.MoveNext())        //{        //    Box b = (Box)enumerator.Current;        //    Console.WriteLine("{0}\t{1}\t{2}\t{3}",        //    b.Height.ToString(), b.Length.ToString(),        //    b.Width.ToString(), b.GetHashCode().ToString());        //}        Console.WriteLine();    }}public class Box : IEquatable<Box>{    public Box(int h, int l, int w)    {        this.Height = h;        this.Length = l;        this.Width = w;    }    public int Height { get; set; }    public int Length { get; set; }    public int Width { get; set; }    // Defines equality using the    // BoxSameDimensions equality comparer.    public bool Equals(Box other)    {        if (new BoxSameDimensions().Equals(this, other))        {            return true;        }        else        {            return false;        }    }    public override bool Equals(object obj)    {        return base.Equals(obj);    }    public override int GetHashCode()    {        return base.GetHashCode();    }}public class BoxCollection : ICollection<Box>{    // The generic enumerator obtained from IEnumerator<Box>    // by GetEnumerator can also be used with the non-generic IEnumerator.    // To avoid a naming conflict, the non-generic IEnumerable method    // is explicitly implemented.    public IEnumerator<Box> GetEnumerator()    {        return new BoxEnumerator(this);    }    IEnumerator IEnumerable.GetEnumerator()    {        return new BoxEnumerator(this);    }    // The inner collection to store objects.    private List<Box> innerCol;    public BoxCollection()    {        innerCol = new List<Box>();    }    // Adds an index to the collection.    public Box this[int index]    {        get { return (Box)innerCol[index]; }        set { innerCol[index] = value; }    }    // Determines if an item is in the collection    // by using the BoxSameDimensions equality comparer.    public bool Contains(Box item)    {        bool found = false;        foreach (Box bx in innerCol)        {            // Equality defined by the Box            // class's implmentation of IEquatable<T>.            if (bx.Equals(item))            {                found = true;            }        }        return found;    }    // Determines if an item is in the    // collection by using a specified equality comparer.    public bool Contains(Box item, EqualityComparer<Box> comp)    {        bool found = false;        foreach (Box bx in innerCol)        {            if (comp.Equals(bx, item))            {                found = true;            }        }        return found;    }    // Adds an item if it is not already in the collection    // as determined by calling the Contains method.    public void Add(Box item)    {        if (!Contains(item))        {            innerCol.Add(item);        }        else        {            Console.WriteLine("A box with {0}x{1}x{2} dimensions was already added to the collection.",                item.Height.ToString(), item.Length.ToString(), item.Width.ToString());        }    }    public void Clear()    {        innerCol.Clear();    }    public void CopyTo(Box[] array, int arrayIndex)    {        if (array == null)           throw new ArgumentNullException("The array cannot be null.");        if (arrayIndex < 0)           throw new ArgumentOutOfRangeException("The starting array index cannot be negative.");        if (Count > array.Length - arrayIndex)           throw new ArgumentException("The destination array has fewer elements than the collection.");        for (int i = 0; i < innerCol.Count; i++) {            array[i + arrayIndex] = innerCol[i];        }    }    public int Count    {        get        {            return innerCol.Count;        }    }    public bool IsReadOnly    {        get { return false; }    }    public bool Remove(Box item)    {        bool result = false;        // Iterate the inner collection to        // find the box to be removed.        for (int i = 0; i < innerCol.Count; i++)        {            Box curBox = (Box)innerCol[i];            if (new BoxSameDimensions().Equals(curBox, item))            {                innerCol.RemoveAt(i);                result = true;                break;            }        }        return result;    }}// Defines the enumerator for the Boxes collection.// (Some prefer this class nested in the collection class.)public class BoxEnumerator : IEnumerator<Box>{    private BoxCollection _collection;    private int curIndex;    private Box curBox;    public BoxEnumerator(BoxCollection collection)    {        _collection = collection;        curIndex = -1;        curBox = default(Box);    }    public bool MoveNext()    {        //Avoids going beyond the end of the collection.        if (++curIndex >= _collection.Count)        {            return false;        }        else        {            // Set current box to next item in collection.            curBox = _collection[curIndex];        }        return true;    }    public void Reset() { curIndex = -1; }    void IDisposable.Dispose() { }    public Box Current    {        get { return curBox; }    }    object IEnumerator.Current    {        get { return Current; }    }}// Defines two boxes as equal if they have the same dimensions.public class BoxSameDimensions : EqualityComparer<Box>{    public override bool Equals(Box b1, Box b2)    {        if (b1.Height == b2.Height && b1.Length == b2.Length                            && b1.Width == b2.Width)        {            return true;        }        else        {            return false;        }    }    public override int GetHashCode(Box bx)    {        int hCode = bx.Height ^ bx.Length ^ bx.Width;        return hCode.GetHashCode();    }}// Defines two boxes as equal if they have the same volume.public class BoxSameVol : EqualityComparer<Box>{    public override bool Equals(Box b1, Box b2)    {        if ((b1.Height * b1.Length * b1.Width) ==                (b2.Height * b2.Length * b2.Width))        {            return true;        }        else        {            return false;        }    }    public override int GetHashCode(Box bx)    {        int hCode = bx.Height ^ bx.Length ^ bx.Width;        Console.WriteLine("HC: {0}", hCode.GetHashCode());        return hCode.GetHashCode();    }}/*This code example displays the following output:================================================A box with 10x4x6 dimensions was already added to the collection.Height  Length  Width   Hash Code10      4       6       461047284       6       10      122893766       10      4       4349552512      8       10      55915408Removing 6x10x4Height  Length  Width   Hash Code10      4       6       461047284       6       10      1228937612      8       10      55915408Contains 8x12x10 by dimensions: FalseContains 8x12x10 by volume: True */

Imports System.CollectionsImports System.Collections.GenericClass Program    Public Shared Sub Main(ByVal args() As String)        Dim bxList As BoxCollection = New BoxCollection()        bxList.Add(New Box(10, 4, 6))        bxList.Add(New Box(4, 6, 10))        bxList.Add(New Box(6, 10, 4))        bxList.Add(New Box(12, 8, 10))        ' Same dimensions. Cannot be added:        bxList.Add(New Box(10, 4, 6))        ' Test the Remove method.        Display(bxList)        Console.WriteLine("Removing 6x10x4")        bxList.Remove(New Box(6, 10, 4))        Display(bxList)        ' Test the Contains method        Dim BoxCheck As Box = New Box(8, 12, 10)        Console.WriteLine("Contains {0}x{1}x{2} by dimensions: {3}", BoxCheck.Height.ToString(),            BoxCheck.Length.ToString(), BoxCheck.Width.ToString(), bxList.Contains(BoxCheck).ToString())        ' Test the Contains method overload with a specified equality comparer.        Console.WriteLine("Contains {0}x{1}x{2} by volume: {3}", BoxCheck.Height.ToString(),            BoxCheck.Length.ToString(), BoxCheck.Width.ToString(),            bxList.Contains(BoxCheck, New BoxSameVol()).ToString())    End Sub    Public Shared Sub Display(ByVal bxList As BoxCollection)        Console.WriteLine(vbLf & "Height" & vbTab & "Length" & vbTab & "Width" & vbTab & "Hash Code")        For Each bx As Box In bxList            Console.WriteLine("{0}" & vbTab & "{1}" & vbTab & "{2}" & vbTab & "{3}", bx.Height.ToString(), bx.Length.ToString(), bx.Width.ToString(), bx.GetHashCode().ToString())        Next        Console.WriteLine()    End SubEnd ClassPublic Class Box : Implements IEquatable(Of Box)    Public Sub New(ByVal h As Integer, ByVal l As Integer, ByVal w As Integer)        Me.Height = h        Me.Length = l        Me.Width = w    End Sub    Private _Height As Integer    Public Property Height() As Integer        Get            Return _Height        End Get        Set(ByVal value As Integer)            _Height = value        End Set    End Property    Private _Length As Integer    Public Property Length() As Integer        Get            Return _Length        End Get        Set(ByVal value As Integer)            _Length = value        End Set    End Property    Private _Width As Integer    Public Property Width() As Integer        Get            Return _Width        End Get        Set(ByVal value As Integer)            _Width = value        End Set    End Property    Public Overloads Function Equals(ByVal other As Box) As Boolean Implements IEquatable(Of Box).Equals        Dim BoxSameDim = New BoxSameDimensions()        If BoxSameDim.Equals(Me, other) Then            Return True        Else            Return False        End If    End Function    Public Overrides Function Equals(ByVal obj As Object) As Boolean        Return MyBase.Equals(obj)    End Function    Public Overrides Function GetHashCode() As Integer        Return MyBase.GetHashCode()    End FunctionEnd ClassPublic Class BoxCollection : Implements ICollection(Of Box)    ' The generic enumerator obtained from IEnumerator<Box> by GetEnumerator can also    ' be used with the non-generic IEnumerator. To avoid a naming conflict,     ' the non-generic IEnumerable method is explicitly implemented.    Public Function GetEnumerator() As IEnumerator(Of Box) _        Implements IEnumerable(Of Box).GetEnumerator        Return New BoxEnumerator(Me)    End Function    Private Function GetEnumerator1() As IEnumerator _        Implements IEnumerable.GetEnumerator        Return Me.GetEnumerator()    End Function    ' The inner collection to store objects.    Private innerCol As List(Of Box)    Public Sub New()        innerCol = New List(Of Box)    End Sub    ' Adds an index to the collection.    Default Public Property Item(ByVal index As Integer) As Box        Get            'If index <> -1 Then            Return CType(innerCol(index), Box)            'End If            'Return Nothing        End Get        Set(ByVal Value As Box)            innerCol(index) = Value        End Set    End Property    ' Determines if an item is in the collection    ' by using the BoxSameDimensions equality comparer.    Public Function Contains(ByVal item As Box) As Boolean _            Implements ICollection(Of Box).Contains        Dim found As Boolean = False        Dim bx As Box        For Each bx In innerCol            If New BoxSameDimensions().Equals(bx, item) Then                found = True            End If        Next        Return found    End Function    ' Determines if an item is in the     ' collection by using a specified equality comparer.    Public Function Contains(ByVal item As Box, _        ByVal comp As EqualityComparer(Of Box)) As Boolean        Dim found As Boolean = False        Dim bx As Box        For Each bx In innerCol            If comp.Equals(bx, item) Then                found = True            End If        Next        Return found    End Function    ' Adds an item if it is not already in the collection    ' as determined by calling the Contains method.    Public Sub Add(ByVal item As Box) _        Implements ICollection(Of Box).Add        If Not Me.Contains(item) Then            innerCol.Add(item)        Else            Console.WriteLine("A box with {0}x{1}x{2} dimensions was already added to the collection.",                item.Height.ToString(), item.Length.ToString(), item.Width.ToString())        End If    End Sub    Public Sub Clear() Implements ICollection(Of Box).Clear        innerCol.Clear()    End Sub    Public Sub CopyTo(array As Box(), arrayIndex As Integer) _            Implements ICollection(Of Box).CopyTo        If array Is Nothing Then           Throw New ArgumentNullException("The array cannot be null.")        Else If arrayIndex < 0 Then           Throw New ArgumentOutOfRangeException("The starting array index cannot be negative.")        Else If Count > array.Length - arrayIndex + 1 Then           Throw New ArgumentException("The destination array has fewer elements than the collection.")        End If                For i As Integer = 0 To innerCol.Count - 1            array(i + arrayIndex) = innerCol(i)        Next    End Sub    Public ReadOnly Property Count() As Integer _            Implements ICollection(Of Box).Count        Get            Return innerCol.Count        End Get    End Property    Public ReadOnly Property IsReadOnly() As Boolean _           Implements ICollection(Of Box).IsReadOnly        Get            Return False        End Get    End Property    Public Function Remove(ByVal item As Box) As Boolean _            Implements ICollection(Of Box).Remove        Dim result As Boolean = False        ' Iterate the inner collection to         ' find the box to be removed.        Dim i As Integer        For i = 0 To innerCol.Count - 1            Dim curBox As Box = CType(innerCol(i), Box)            If New BoxSameDimensions().Equals(curBox, item) Then                innerCol.RemoveAt(i)                result = True                Exit For            End If        Next        Return result    End FunctionEnd Class' Defines the enumerator for the Boxes collection.' (Some prefer this class nested in the collection class.)Public Class BoxEnumerator    Implements IEnumerator(Of Box)    Private _collection As BoxCollection    Private curIndex As Integer    Private curBox As Box    Public Sub New(ByVal collection As BoxCollection)        MyBase.New()        _collection = collection        curIndex = -1        curBox = Nothing    End Sub    Private Property Box As Box    Public Function MoveNext() As Boolean _        Implements IEnumerator(Of Box).MoveNext        curIndex = curIndex + 1        If curIndex = _collection.Count Then            ' Avoids going beyond the end of the collection.            Return False        Else            'Set current box to next item in collection.            curBox = _collection(curIndex)        End If        Return True    End Function    Public Sub Reset() _        Implements IEnumerator(Of Box).Reset        curIndex = -1    End Sub    Public Sub Dispose() _        Implements IEnumerator(Of Box).Dispose    End Sub    Public ReadOnly Property Current() As Box _        Implements IEnumerator(Of Box).Current        Get            If curBox Is Nothing Then                Throw New InvalidOperationException()            End If            Return curBox        End Get    End Property    Private ReadOnly Property Current1() As Object _        Implements IEnumerator.Current        Get            Return Me.Current        End Get    End PropertyEnd Class' Defines two boxes as equal if they have the same dimensions.Public Class BoxSameDimensions    Inherits EqualityComparer(Of Box)    Public Overrides Function Equals(ByVal b1 As Box, ByVal b2 As Box) As Boolean        If b1.Height = b2.Height And b1.Length = b2.Length And b1.Width = b2.Width Then            Return True        Else            Return False        End If    End Function    Public Overrides Function GetHashCode(ByVal bx As Box) As Integer        Dim hCode As Integer = bx.Height ^ bx.Length ^ bx.Width        Return hCode.GetHashCode()    End FunctionEnd Class' Defines two boxes as equal if they have the same volume.Public Class BoxSameVol    Inherits EqualityComparer(Of Box)    Public Overrides Function Equals(ByVal b1 As Box, ByVal b2 As Box) As Boolean        If (b1.Height * b1.Length * b1.Width) _            = (b2.Height * b2.Length * b2.Width) Then            Return True        Else            Return False        End If    End Function    Public Overrides Function GetHashCode(ByVal bx As Box) As Integer        Dim hCode As Integer = bx.Height ^ bx.Length ^ bx.Width        Console.WriteLine("HC: {0}", hCode.GetHashCode())        Return hCode.GetHashCode()    End FunctionEnd Class'  This code example displays the following output:'  ================================================''  A box with 10x4x6 dimensions was already added to the collection.''  Height  Length  Width   Hash Code'  10      4       6       46104728'  4       6       10      12289376'  6       10      4       43495525'  12      8       10      55915408''  Removing 6x10x4''  Height  Length  Width   Hash Code'  10      4       6       46104728'  4       6       10      12289376'  12      8       10      55915408''  Contains 8x12x10 by dimensions: False'  Contains 8x12x10 by volume: True'

Remarks

TheICollection<T> interface is the base interface for classes in theSystem.Collections.Generic namespace.

TheICollection<T> interface extendsIEnumerable<T>;IDictionary<TKey,TValue> andIList<T> are more specialized interfaces that extendICollection<T>. AIDictionary<TKey,TValue> implementation is a collection of key/value pairs, like theDictionary<TKey,TValue> class. AIList<T> implementation is a collection of values, and its members can be accessed by index, like theList<T> class.

If neither theIDictionary<TKey,TValue> interface nor theIList<T> interface meet the requirements of the required collection, derive the new collection class from theICollection<T> interface instead for more flexibility.

See also

• IDictionary<TKey,TValue>
• IList<T>
• System.Collections