IList.Add Method (Object)
.NET Framework (current version)
Adds an item to the IList.
Assembly: mscorlib (in mscorlib.dll)
Parameters
- value
-
Type:
System.Object
The object to add to the IList.
Return Value
Type: System.Int32The position into which the new element was inserted, or -1 to indicate that the item was not inserted into the collection.
| Exception | Condition |
|---|---|
| NotSupportedException |
The following example demonstrates the implementation of the IList interface to create a simple, fixed-size list. This code is part of a larger example for the IList interface.
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
Universal Windows Platform
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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