IList Interface

Represents a non-generic collection of objects that can be individually accessed by index.

Namespace:  System.Collections
Assembly:  mscorlib (in mscorlib.dll)

'Declaration
<ComVisibleAttribute(True)> _
Public Interface IList _
	Inherits ICollection, IEnumerable

The IList type exposes the following members.

  NameDescription
Public propertySupported by the XNA FrameworkSupported by Portable Class LibraryCountGets the number of elements contained in the ICollection. (Inherited from ICollection.)
Public propertySupported by the XNA FrameworkSupported by Portable Class LibraryIsFixedSizeGets a value indicating whether the IList has a fixed size.
Public propertySupported by the XNA FrameworkSupported by Portable Class LibraryIsReadOnlyGets a value indicating whether the IList is read-only.
Public propertySupported by the XNA FrameworkSupported by Portable Class LibraryIsSynchronizedGets a value indicating whether access to the ICollection is synchronized (thread safe). (Inherited from ICollection.)
Public propertySupported by the XNA FrameworkSupported by Portable Class LibraryItemGets or sets the element at the specified index.
Public propertySupported by the XNA FrameworkSupported by Portable Class LibrarySyncRootGets an object that can be used to synchronize access to the ICollection. (Inherited from ICollection.)
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  NameDescription
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryAddAdds an item to the IList.
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryClearRemoves all items from the IList.
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryContainsDetermines whether the IList contains a specific value.
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryCopyToCopies the elements of the ICollection to an Array, starting at a particular Array index. (Inherited from ICollection.)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryGetEnumeratorReturns an enumerator that iterates through a collection. (Inherited from IEnumerable.)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryIndexOfDetermines the index of a specific item in the IList.
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryInsertInserts an item to the IList at the specified index.
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryRemoveRemoves the first occurrence of a specific object from the IList.
Public methodSupported by the XNA FrameworkSupported by Portable Class LibraryRemoveAtRemoves the IList item at the specified index.
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  NameDescription
Public Extension MethodAsParallelEnables parallelization of a query. (Defined by ParallelEnumerable.)
Public Extension MethodSupported by Portable Class LibraryAsQueryableConverts an IEnumerable to an IQueryable. (Defined by Queryable.)
Public Extension MethodSupported by the XNA FrameworkSupported by Portable Class LibraryCast(Of TResult)Casts the elements of an IEnumerable to the specified type. (Defined by Enumerable.)
Public Extension MethodSupported by the XNA FrameworkSupported by Portable Class LibraryOfType(Of TResult)Filters the elements of an IEnumerable based on a specified type. (Defined by Enumerable.)
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IList is a descendant of the ICollection interface and is the base interface of all non-generic lists. IList implementations fall into three categories: read-only, fixed-size, and variable-size. A read-only IList cannot be modified. A fixed-size IList does not allow the addition or removal of elements, but it allows the modification of existing elements. A variable-size IList allows the addition, removal, and modification of elements.

For the generic version of this interface, see System.Collections.Generic.IList(Of T).

The following example demonstrates the implementation of the IList interface to create a simple list, fixed-size list.


Imports System
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': {0}", myList.Contains("three"))
        Console.WriteLine("List contains 'ten': {0}", myList.Contains("ten"))

    End Sub
End Class ' class Program

Public Class SimpleList
    Implements IList

    Private _contents(8) 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 - 1) Then

            _contents(_count) = value
            _count = _count + 1

            Return (_count - 1)

        Else

            Return -1
        End If
    End Function

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

    Public Function Contains(ByVal value As Object) As Boolean Implements IList.Contains

        Dim inList As Boolean = False

        Dim i As Integer
        For i = 0 To Count

            If _contents(i) = value Then

                inList = True
                Exit For

            End If

        Next i

        Return inList
    End Function

    Public Function IndexOf(ByVal value As Object) As Integer Implements IList.IndexOf

        Dim itemIndex As Integer = -1

        Dim i As Integer
        For i = 0 To Count

            If _contents(i) = value Then

                itemIndex = i
                Exit For

            End If

        Next i

        Return itemIndex
    End Function

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

        If (_count + 1) <= (_contents.Length - 1) And (index < Count) And (index >= 0) Then

            _count = _count + 1

            Dim i As Integer
            For i = Count - 1 To index

                _contents(i) = _contents(i - 1)
            Next i

            _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 And index < Count Then

            Dim i As Integer
            For i = index To Count - 1

                _contents(i) = _contents(i + 1)
            Next i
            _count = _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
        Dim j As Integer = index
        Dim i As Integer
        For i = 0 To Count
            array.SetValue(_contents(i), j)
            j = j + 1
        Next i
    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 Exception("The method or operation is not implemented.")
    End Function

    Public Sub PrintContents()

        Console.WriteLine("List has a capacity of {0} and currently has {1} elements.", _contents.Length - 1, _count)
        Console.Write("List contents:")

        Dim i As Integer
        For i = 0 To Count

            Console.Write(" {0}", _contents(i))
        Next i

        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


.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
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