IList Interfaccia

Definizione

Rappresenta una raccolta non generica di oggetti a cui è possibile accedere singolarmente tramite indice.

public interface class IList : System::Collections::ICollection
public interface IList : System.Collections.ICollection
[System.Runtime.InteropServices.ComVisible(true)]
public interface IList : System.Collections.ICollection
type IList = interface
    interface ICollection
    interface IEnumerable
[<System.Runtime.InteropServices.ComVisible(true)>]
type IList = interface
    interface ICollection
    interface IEnumerable
Public Interface IList
Implements ICollection
Derivato
Attributi
Implementazioni

Esempio

Nell'esempio riportato di seguito viene illustrata l'implementazione dell'interfaccia IList per creare un elenco semplice di dimensione fissa.

using System;
using System.Collections;

class Program
{
    static void Main()
    {
        var test = new SimpleList();

        // Populate the List.
        Console.WriteLine("Populate the List");
        test.Add("one");
        test.Add("two");
        test.Add("three");
        test.Add("four");
        test.Add("five");
        test.Add("six");
        test.Add("seven");
        test.Add("eight");
        test.PrintContents();
        Console.WriteLine();

        // Remove elements from the list.
        Console.WriteLine("Remove elements from the list");
        test.Remove("six");
        test.Remove("eight");
        test.PrintContents();
        Console.WriteLine();

        // Add an element to the end of the list.
        Console.WriteLine("Add an element to the end of the list");
        test.Add("nine");
        test.PrintContents();
        Console.WriteLine();

        // Insert an element into the middle of the list.
        Console.WriteLine("Insert an element into the middle of the list");
        test.Insert(4, "number");
        test.PrintContents();
        Console.WriteLine();

        // Check for specific elements in the list.
        Console.WriteLine("Check for specific elements in the list");
        Console.WriteLine($"List contains \"three\": {test.Contains("three")}");
        Console.WriteLine($"List contains \"ten\": {test.Contains("ten")}");
    }
}

class SimpleList : IList
{
    private object[] _contents = new object[8];
    private int _count;

    public SimpleList()
    {
        _count = 0;
    }

    // IList Members
    public int Add(object value)
    {
        if (_count < _contents.Length)
        {
            _contents[_count] = value;
            _count++;

            return (_count - 1);
        }

        return -1;
    }

    public void Clear()
    {
        _count = 0;
    }

    public bool Contains(object value)
    {
        for (int i = 0; i < Count; i++)
        {
            if (_contents[i] == value)
            {
                return true;
            }
        }
        return false;
    }

    public int IndexOf(object value)
    {
        for (int i = 0; i < Count; i++)
        {
            if (_contents[i] == value)
            {
                return i;
            }
        }
        return -1;
    }

    public void Insert(int index, object value)
    {
        if ((_count + 1 <= _contents.Length) && (index < Count) && (index >= 0))
        {
            _count++;

            for (int i = Count - 1; i > index; i--)
            {
                _contents[i] = _contents[i - 1];
            }
            _contents[index] = value;
        }
    }

    public bool IsFixedSize
    {
        get
        {
            return true;
        }
    }

    public bool IsReadOnly
    {
        get
        {
            return false;
        }
    }

    public void Remove(object value)
    {
        RemoveAt(IndexOf(value));
    }

    public void RemoveAt(int index)
    {
        if ((index >= 0) && (index < Count))
        {
            for (int i = index; i < Count - 1; i++)
            {
                _contents[i] = _contents[i + 1];
            }
            _count--;
        }
    }

    public object this[int index]
    {
        get
        {
            return _contents[index];
        }
        set
        {
            _contents[index] = value;
        }
    }

    // ICollection members.

    public void CopyTo(Array array, int index)
    {
        for (int i = 0; i < Count; i++)
        {
            array.SetValue(_contents[i], index++);
        }
    }

    public int Count
    {
        get
        {
            return _count;
        }
    }

    public bool IsSynchronized
    {
        get
        {
            return false;
        }
    }

    // Return the current instance since the underlying store is not
    // publicly available.
    public object SyncRoot
    {
        get
        {
            return this;
        }
    }

    // IEnumerable Members

    public IEnumerator GetEnumerator()
    {
        // Refer to the IEnumerator documentation for an example of
        // implementing an enumerator.
        throw new NotImplementedException("The method or operation is not implemented.");
    }

    public void PrintContents()
    {
        Console.WriteLine($"List has a capacity of {_contents.Length} and currently has {_count} elements.");
        Console.Write("List contents:");
        for (int i = 0; i < Count; i++)
        {
            Console.Write($" {_contents[i]}");
        }
        Console.WriteLine();
    }
}

// This code produces output similar to the following:
// Populate the List:
// List has a capacity of 8 and currently has 8 elements.
// List contents: one two three four five six seven eight
//
// Remove elements from the list:
// List has a capacity of 8 and currently has 6 elements.
// List contents: one two three four five seven
//
// Add an element to the end of the list:
// List has a capacity of 8 and currently has 7 elements.
// List contents: one two three four five seven nine
//
// Insert an element into the middle of the list:
// List has a capacity of 8 and currently has 8 elements.
// List contents: one two three four number five seven nine
//
// Check for specific elements in the list:
// List contains "three": True
// List contains "ten": False
Imports System.Collections

Public Class Program
    Shared Sub Main()

        Dim myList As New SimpleList()

        ' Populate the List.
        Console.WriteLine("Populate the List")
        myList.Add("one")
        myList.Add("two")
        myList.Add("three")
        myList.Add("four")
        myList.Add("five")
        myList.Add("six")
        myList.Add("seven")
        myList.Add("eight")
        myList.PrintContents()
        Console.WriteLine()

        ' Remove elements from the list.
        Console.WriteLine("Remove elements from the list")
        myList.Remove("six")
        myList.Remove("eight")
        myList.PrintContents()
        Console.WriteLine()

        ' Add an element to the end of the list.
        Console.WriteLine("Add an element to the end of the list")
        myList.Add("nine")
        myList.PrintContents()
        Console.WriteLine()

        ' Insert an element into the middle of the list.
        Console.WriteLine("Insert an element into the middle of the list")
        myList.Insert(4, "number")
        myList.PrintContents()
        Console.WriteLine()

        ' Check for specific elements in the list.
        Console.WriteLine("Check for specific elements in the list")
        Console.WriteLine($"List contains 'three': {myList.Contains("three")}")
        Console.WriteLine($"List contains 'ten': {myList.Contains("ten")}")
    End Sub
End Class

Public Class SimpleList
    Implements IList

    Private _contents(7) As Object
    Private _count As Integer

    Public Sub New()

        _count = 0
    End Sub

    ' IList members.
    Public Function Add(ByVal value As Object) As Integer Implements IList.Add
        If _count < _contents.Length Then
            _contents(_count) = value
            _count += 1

            Return _count - 1
        End If

        Return -1
    End Function

    Public Sub Clear() Implements IList.Clear
        _count = 0
    End Sub

    Public Function Contains(ByVal value As Object) As Boolean Implements IList.Contains
        For i As Integer = 0 To Count - 1
            If _contents(i) = value Then Return True
        Next

        Return False
    End Function

    Public Function IndexOf(ByVal value As Object) As Integer Implements IList.IndexOf
        For i As Integer = 0 To Count - 1
            If _contents(i) = value Then Return i
        Next
        Return -1
    End Function

    Public Sub Insert(ByVal index As Integer, ByVal value As Object) Implements IList.Insert

        If _count + 1 <= _contents.Length AndAlso index < Count AndAlso index >= 0 Then
            _count += 1

            For i As Integer = Count - 1 To index Step -1
                _contents(i) = _contents(i - 1)
            Next
            _contents(index) = value
        End If
    End Sub

    Public ReadOnly Property IsFixedSize() As Boolean Implements IList.IsFixedSize
        Get
            Return True
        End Get
    End Property

    Public ReadOnly Property IsReadOnly() As Boolean Implements IList.IsReadOnly
        Get
            Return False
        End Get
    End Property

    Public Sub Remove(ByVal value As Object) Implements IList.Remove
        RemoveAt(IndexOf(value))
    End Sub

    Public Sub RemoveAt(ByVal index As Integer) Implements IList.RemoveAt

        if index >= 0 AndAlso index < Count Then
            for i As Integer = index To Count - 2
                _contents(i) = _contents(i + 1)
            Next
            _count -= 1
        End If
    End Sub

    Public Property Item(ByVal index As Integer) As Object Implements IList.Item
        Get
            Return _contents(index)
        End Get

        Set(ByVal value As Object)
            _contents(index) = value
        End Set
    End Property

    ' ICollection members.
    Public Sub CopyTo(ByVal array As Array, ByVal index As Integer) Implements ICollection.CopyTo
        For i As Integer = 0 To Count - 1
            array.SetValue(_contents(i), index)
            index += 1
        Next
    End Sub

    Public ReadOnly Property Count() As Integer Implements ICollection.Count
        Get
            Return _count
        End Get
    End Property

    Public ReadOnly Property IsSynchronized() As Boolean Implements ICollection.IsSynchronized
        Get
            Return False
        End Get
    End Property

    ' Return the current instance since the underlying store is not
    ' publicly available.
    Public ReadOnly Property SyncRoot() As Object Implements ICollection.SyncRoot
        Get
            Return Me
        End Get
    End Property

    ' IEnumerable members.
    Public Function GetEnumerator() As IEnumerator Implements IEnumerable.GetEnumerator

        ' Refer to the IEnumerator documentation for an example of
        ' implementing an enumerator.
        Throw New NotImplementedException("The method or operation is not implemented.")
    End Function

    Public Sub PrintContents()
        Console.WriteLine($"List has a capacity of {_contents.Length} and currently has {_count} elements.")
        Console.Write("List contents:")

        For i As Integer = 0 To Count - 1
            Console.Write($" {_contents(i)}")
        Next

        Console.WriteLine()
    End Sub
End Class

' This code produces output similar to the following:
' Populate the List:
' List has a capacity of 8 and currently has 8 elements.
' List contents: one two three four five six seven eight
'
' Remove elements from the list:
' List has a capacity of 8 and currently has 6 elements.
' List contents: one two three four five seven
'
' Add an element to the end of the list:
' List has a capacity of 8 and currently has 7 elements.
' List contents: one two three four five seven nine
'
' Insert an element into the middle of the list:
' List has a capacity of 8 and currently has 8 elements.
' List contents: one two three four number five seven nine
'
' Check for specific elements in the list:
' List contains "three": True
' List contains "ten": False

Commenti

IList è un discendente ICollection dell'interfaccia ed è l'interfaccia di base di tutti gli elenchi non generici. IList Le implementazioni di rientrano in tre categorie: di sola lettura, a dimensione fissa e a dimensione variabile. Non è possibile modificare IList un oggetto di sola lettura. Una dimensione fissa IList non consente l'aggiunta o la rimozione di elementi, ma consente la modifica degli elementi esistenti. Una dimensione variabile IList consente l'aggiunta, la rimozione e la modifica degli elementi.

Per la versione generica di questa interfaccia, vedere System.Collections.Generic.IList<T> .

Proprietà

Count

Ottiene il numero di elementi contenuti in ICollection.

(Ereditato da ICollection)
IsFixedSize

Ottiene un valore che indica se IList ha dimensioni fisse.

IsReadOnly

Ottiene un valore che indica se IList è di sola lettura.

IsSynchronized

Ottiene un valore che indica se l'accesso a ICollection è sincronizzato (thread-safe).

(Ereditato da ICollection)
Item[Int32]

Ottiene o imposta l'elemento in corrispondenza dell'indice specificato.

SyncRoot

Ottiene un oggetto che può essere usato per sincronizzare l'accesso a ICollection.

(Ereditato da ICollection)

Metodi

Add(Object)

Aggiunge un elemento a IList.

Clear()

Rimuove tutti gli elementi da IList.

Contains(Object)

Stabilisce se IList contiene un valore specifico.

CopyTo(Array, Int32)

Copia gli elementi di ICollection in Array a partire da un particolare indice Array.

(Ereditato da ICollection)
GetEnumerator()

Restituisce un enumeratore che consente di eseguire l'iterazione di una raccolta.

(Ereditato da IEnumerable)
IndexOf(Object)

Determina l'indice di un elemento specifico in IList.

Insert(Int32, Object)

Inserisce un elemento in IList in corrispondenza dell'indice specificato.

Remove(Object)

Rimuove la prima occorrenza di un oggetto specifico da IList.

RemoveAt(Int32)

Rimuove l'elemento IList in corrispondenza dell'indice specificato.

Metodi di estensione

Cast<TResult>(IEnumerable)

Esegue il cast degli elementi di un oggetto IEnumerable nel tipo specificato.

OfType<TResult>(IEnumerable)

Filtra gli elementi di un oggetto IEnumerable in base a un tipo specificato.

AsParallel(IEnumerable)

Consente la parallelizzazione di una query.

AsQueryable(IEnumerable)

Converte un oggetto IEnumerable in un oggetto IQueryable.

Si applica a

Vedi anche