CollectionBase.System.Collections.IList.Item-Eigenschaft
Hinweis: Dieser Namespace oder Member bzw. diese Klasse wird nur von .NET Framework, Version 1.1, unterstützt.
Ruft das Element am angegebenen Index ab oder legt dieses fest.
[C#] In C# stellt diese Eigenschaft den Indexer für die CollectionBase-Klasse dar.
Private Default Property Item( _
ByVal index As Integer _) As Object Implements IList.Item
[C#]
object IList.this[
intindex] {get; set;}
[C++]
private: __property Object* System::Collections::IList::get_Item(intindex);private: __property void System::Collections::IList::set_Item(intindex, Object*);
[JScript]
private function get IList.get_Item(index : int) : Object;private function set IList.set_Item(index : int, value : Object);- oder -private function get IList.get_Item(index : int) : Object;private function set IList.set_Item(index : int, value : Object);
[JScript] In JScript können Sie die durch einen Typ definierten indizierten Standardeigenschaften verwenden, jedoch keine eigenen explizit definieren. Durch Angabe des expando-Attributs für eine Klasse wird allerdings automatisch eine indizierte Standardeigenschaft mit dem Typ Object und dem Indextyp String bereitgestellt.
Argumente [JScript]
- index
Der nullbasierte Index des Elements, das abgerufen oder festgelegt werden soll.
Parameter [Visual Basic, C#, C++]
- index
Der nullbasierte Index des Elements, das abgerufen oder festgelegt werden soll.
Eigenschaftenwert
Das Element am angegebenen Index.
Implementiert
Ausnahmen
| Ausnahmetyp | Bedingung |
|---|---|
| ArgumentOutOfRangeException | index ist kleiner als 0.
– oder – index ist größer oder gleich Count. |
Hinweise
Diese Eigenschaft ermöglicht den Zugriff auf ein bestimmtes Element in der Auflistung mit folgender Syntax: myCollection[index].
Beispiel
[Visual Basic, C#, C++] Im folgenden Codebeispiel wird die CollectionBase-Klasse implementiert und diese Implementierung zum Erstellen einer Auflistung von Int16-Objekten verwendet.
Imports System
Imports System.Collections
Public Class Int16Collection
Inherits CollectionBase
Default Public Property Item(index As Integer) As Int16
Get
Return CType(List(index), Int16)
End Get
Set
List(index) = value
End Set
End Property
Public Function Add(value As Int16) As Integer
Return List.Add(value)
End Function 'Add
Public Function IndexOf(value As Int16) As Integer
Return List.IndexOf(value)
End Function 'IndexOf
Public Sub Insert(index As Integer, value As Int16)
List.Insert(index, value)
End Sub 'Insert
Public Sub Remove(value As Int16)
List.Remove(value)
End Sub 'Remove
Public Function Contains(value As Int16) As Boolean
' If value is not of type Int16, this will return false.
Return List.Contains(value)
End Function 'Contains
Protected Overrides Sub OnInsert(index As Integer, value As [Object])
' Insert additional code to be run only when inserting values.
End Sub 'OnInsert
Protected Overrides Sub OnRemove(index As Integer, value As [Object])
' Insert additional code to be run only when removing values.
End Sub 'OnRemove
Protected Overrides Sub OnSet(index As Integer, oldValue As [Object], newValue As [Object])
' Insert additional code to be run only when setting values.
End Sub 'OnSet
Protected Overrides Sub OnValidate(value As [Object])
If Not value.GetType() Is Type.GetType("System.Int16") Then
Throw New ArgumentException("value must be of type Int16.", "value")
End If
End Sub 'OnValidate
End Class 'Int16Collection
Public Class SamplesCollectionBase
Public Shared Sub Main()
' Creates and initializes a new CollectionBase.
Dim myI16 As New Int16Collection()
' Adds elements to the collection.
myI16.Add( 1 )
myI16.Add( 2 )
myI16.Add( 3 )
myI16.Add( 5 )
myI16.Add( 7 )
' Displays the contents of the collection using the enumerator.
Console.WriteLine("Initial contents of the collection:")
PrintIndexAndValues(myI16)
' Searches the collection with Contains and IndexOf.
Console.WriteLine("Contains 3: {0}", myI16.Contains(3))
Console.WriteLine("2 is at index {0}.", myI16.IndexOf(2))
Console.WriteLine()
' Inserts an element into the collection at index 3.
myI16.Insert(3, 13)
Console.WriteLine("Contents of the collection after inserting at index 3:")
PrintIndexAndValues(myI16)
' Gets and sets an element using the index.
myI16(4) = 123
Console.WriteLine("Contents of the collection after setting the element at index 4 to 123:")
PrintIndexAndValues(myI16)
' Removes an element from the collection.
myI16.Remove(2)
' Displays the contents of the collection using the index.
Console.WriteLine("Contents of the collection after removing the element 2:")
Dim i As Integer
For i = 0 To myI16.Count - 1
Console.WriteLine(" [{0}]: {1}", i, myI16(i))
Next i
End Sub 'Main
Public Shared Sub PrintIndexAndValues(myCol As Int16Collection)
Dim i As Integer = 0
Dim myEnumerator As System.Collections.IEnumerator = myCol.GetEnumerator()
While myEnumerator.MoveNext()
Console.WriteLine(" [{0}]: {1}", i, myEnumerator.Current)
i += 1
End While
Console.WriteLine()
End Sub 'PrintIndexAndValues
End Class 'SamplesCollectionBase
'This code produces the following output.
'
'Initial contents of the collection:
' [0]: 1
' [1]: 2
' [2]: 3
' [3]: 5
' [4]: 7
'
'Contains 3: True
'2 is at index 1.
'
'Contents of the collection after inserting at index 3:
' [0]: 1
' [1]: 2
' [2]: 3
' [3]: 13
' [4]: 5
' [5]: 7
'
'Contents of the collection after setting the element at index 4 to 123:
' [0]: 1
' [1]: 2
' [2]: 3
' [3]: 13
' [4]: 123
' [5]: 7
'
'Contents of the collection after removing the element 2:
' [0]: 1
' [1]: 3
' [2]: 13
' [3]: 123
' [4]: 7
[C#]
using System;
using System.Collections;
public class Int16Collection : CollectionBase {
public Int16 this[ int index ] {
get {
return( (Int16) List[index] );
}
set {
List[index] = value;
}
}
public int Add( Int16 value ) {
return( List.Add( value ) );
}
public int IndexOf( Int16 value ) {
return( List.IndexOf( value ) );
}
public void Insert( int index, Int16 value ) {
List.Insert( index, value );
}
public void Remove( Int16 value ) {
List.Remove( value );
}
public bool Contains( Int16 value ) {
// If value is not of type Int16, this will return false.
return( List.Contains( value ) );
}
protected override void OnInsert( int index, Object value ) {
// Insert additional code to be run only when inserting values.
}
protected override void OnRemove( int index, Object value ) {
// Insert additional code to be run only when removing values.
}
protected override void OnSet( int index, Object oldValue, Object newValue ) {
// Insert additional code to be run only when setting values.
}
protected override void OnValidate( Object value ) {
if ( value.GetType() != Type.GetType("System.Int16") )
throw new ArgumentException( "value must be of type Int16.", "value" );
}
}
public class SamplesCollectionBase {
public static void Main() {
// Creates and initializes a new CollectionBase.
Int16Collection myI16 = new Int16Collection();
// Adds elements to the collection.
myI16.Add( (Int16) 1 );
myI16.Add( (Int16) 2 );
myI16.Add( (Int16) 3 );
myI16.Add( (Int16) 5 );
myI16.Add( (Int16) 7 );
// Displays the contents of the collection using the enumerator.
Console.WriteLine( "Initial contents of the collection:" );
PrintIndexAndValues( myI16 );
// Searches the collection with Contains and IndexOf.
Console.WriteLine( "Contains 3: {0}", myI16.Contains( 3 ) );
Console.WriteLine( "2 is at index {0}.", myI16.IndexOf( 2 ) );
Console.WriteLine();
// Inserts an element into the collection at index 3.
myI16.Insert( 3, (Int16) 13 );
Console.WriteLine( "Contents of the collection after inserting at index 3:" );
PrintIndexAndValues( myI16 );
// Gets and sets an element using the index.
myI16[4] = 123;
Console.WriteLine( "Contents of the collection after setting the element at index 4 to 123:" );
PrintIndexAndValues( myI16 );
// Removes an element from the collection.
myI16.Remove( (Int16) 2 );
// Displays the contents of the collection using the index.
Console.WriteLine( "Contents of the collection after removing the element 2:" );
for ( int i = 0; i < myI16.Count; i++ ) {
Console.WriteLine( " [{0}]: {1}", i, myI16[i] );
}
}
public static void PrintIndexAndValues( Int16Collection myCol ) {
int i = 0;
System.Collections.IEnumerator myEnumerator = myCol.GetEnumerator();
while ( myEnumerator.MoveNext() )
Console.WriteLine( " [{0}]: {1}", i++, myEnumerator.Current );
Console.WriteLine();
}
}
/*
This code produces the following output.
Initial contents of the collection:
[0]: 1
[1]: 2
[2]: 3
[3]: 5
[4]: 7
Contains 3: True
2 is at index 1.
Contents of the collection after inserting at index 3:
[0]: 1
[1]: 2
[2]: 3
[3]: 13
[4]: 5
[5]: 7
Contents of the collection after setting the element at index 4 to 123:
[0]: 1
[1]: 2
[2]: 3
[3]: 13
[4]: 123
[5]: 7
Contents of the collection after removing the element 2:
[0]: 1
[1]: 3
[2]: 13
[3]: 123
[4]: 7
*/
[C++]
#using <mscorlib.dll>
using namespace System;
using namespace System::Collections;
public __gc class Int16Collection : public CollectionBase
{
public:
__property Int16 get_Item( int index )
{
return *__try_cast<__box Int16*>(List->Item[index]);
}
__property void set_Item( int index, Int16 value )
{
List->Item[index] = __box(value);
}
int Add(Int16 value)
{
return(List->Add(__box(value)));
}
int IndexOf(Int16 value)
{
return(List->IndexOf(__box(value)));
}
void Insert(int index, Int16 value)
{
List->Insert(index, __box(value));
}
void Remove(Int16 value)
{
List->Remove(__box(value));
}
bool Contains(Int16 value)
{
// If value is not of type Int16, this will return false.
return(List->Contains(__box(value)));
}
protected:
void OnInsert(int index, Object* value)
{
// Insert additional code to be run only when inserting values.
}
void OnRemove(int index, Object* value)
{
// Insert additional code to be run only when removing values.
}
void OnSet(int index, Object* oldValue, Object* newValue)
{
// Insert additional code to be run only when setting values.
}
void OnValidate(Object* value)
{
if (value->GetType() != Type::GetType(S"System.Int16"))
throw new ArgumentException(S"value must be of type Int16.", S"value");
}
};
void PrintIndexAndValues(Int16Collection* myCol)
{
int i = 0;
System::Collections::IEnumerator* myEnumerator = myCol->GetEnumerator();
while (myEnumerator->MoveNext())
Console::WriteLine(S" [ {0}]: {1}", __box(i++), myEnumerator->Current);
Console::WriteLine();
}
int main()
{
// Creates and initializes a new CollectionBase.
Int16Collection* myI16 = new Int16Collection();
// Adds elements to the collection.
myI16->Add((Int16) 1);
myI16->Add((Int16) 2);
myI16->Add((Int16) 3);
myI16->Add((Int16) 5);
myI16->Add((Int16) 7);
// Displays the contents of the collection using the enumerator.
Console::WriteLine(S"Initial contents of the collection:");
PrintIndexAndValues(myI16);
// Searches the collection with Contains and IndexOf.
Console::WriteLine(S"Contains 3: {0}", __box(myI16->Contains(3)));
Console::WriteLine(S"2 is at index {0}.", __box(myI16->IndexOf(2)));
Console::WriteLine();
// Inserts an element into the collection at index 3.
myI16->Insert(3, (Int16) 13);
Console::WriteLine(S"Contents of the collection after inserting at index 3:");
PrintIndexAndValues(myI16);
// Gets and sets an element using the index.
myI16->Item[4] = 123;
Console::WriteLine(S"Contents of the collection after setting the element at index 4 to 123:");
PrintIndexAndValues(myI16);
// Removes an element from the collection.
myI16->Remove((Int16) 2);
// Displays the contents of the collection using the index.
Console::WriteLine(S"Contents of the collection after removing the element 2:");
for (int i = 0; i < myI16->Count; i++)
{
Console::WriteLine(S" [ {0}]: {1}", __box(i), __box(myI16->Item[i]));
}
}
/*
This code produces the following output.
Initial contents of the collection:
[0]: 1
[1]: 2
[2]: 3
[3]: 5
[4]: 7
Contains 3: True
2 is at index 1.
Contents of the collection after inserting at index 3:
[0]: 1
[1]: 2
[2]: 3
[3]: 13
[4]: 5
[5]: 7
Contents of the collection after setting the element at index 4 to 123:
[0]: 1
[1]: 2
[2]: 3
[3]: 13
[4]: 123
[5]: 7
Contents of the collection after removing the element 2:
[0]: 1
[1]: 3
[2]: 13
[3]: 123
[4]: 7
*/
[JScript] Für JScript ist kein Beispiel verfügbar. Klicken Sie zum Anzeigen eines Beispiels für Visual Basic, C# oder C++ in der linken oberen Ecke der Seite auf die Schaltfläche "Sprachfilter" .gif)
.
Anforderungen
Plattformen: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003-Familie
Siehe auch
CollectionBase-Klasse | CollectionBase-Member | System.Collections-Namespace | Count