DictionaryBase.System.Collections.IDictionary.Item-Eigenschaft
Hinweis: Dieser Namespace oder Member bzw. diese Klasse wird nur von .NET Framework, Version 1.1, unterstützt.
Ruft den Wert ab, der dem angegebenen Schlüssel zugeordnet ist, oder legt diesen fest.
[C#] In C# stellt diese Eigenschaft den Indexer für die DictionaryBase-Klasse dar.
Private Default Property Item( _
ByVal key As Object _) As Object Implements IDictionary.Item
[C#]
object IDictionary.this[
objectkey] {get; set;}
[C++]
private: __property Object* System::Collections::IDictionary::get_Item(Object* key);private: __property void System::Collections::IDictionary::set_Item(Object* key, Object*);
[JScript]
private function get IDictionary.get_Item(key : Object) : Object;private function set IDictionary.set_Item(key : Object, value : Object);- oder -private function get IDictionary.get_Item(key : Object) : Object;private function set IDictionary.set_Item(key : Object, 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]
- key
Der Schlüssel, dessen Wert abgerufen oder festgelegt werden soll.
Parameter [Visual Basic, C#, C++]
- key
Der Schlüssel, dessen Wert abgerufen oder festgelegt werden soll.
Eigenschaftenwert
Der dem angegebenen Schlüssel zugeordnete Wert. Wenn der angegebene Schlüssel nicht gefunden werden kann, wird beim Abrufen dieses Schlüssels NULL (Nothing in Visual Basic) zurückgegeben. Beim Festlegen wird ein neues Element mit dem angegebenen Schlüssel erstellt.
Implementiert
Ausnahmen
| Ausnahmetyp | Bedingung |
|---|---|
| ArgumentNullException | key ist NULL (Nothing in Visual Basic). |
| NotSupportedException | Die Eigenschaft wird festgelegt, und DictionaryBase ist schreibgeschützt.
– oder – Die Eigenschaft wird festgelegt, key ist in der Auflistung nicht vorhanden, und DictionaryBase hat eine feste Größe. |
Hinweise
Diese Eigenschaft ermöglicht den Zugriff auf ein bestimmtes Element in der Auflistung mit folgender Syntax: myCollection[key].
Wenn der angegebene Schlüssel beim Festlegen dieser Eigenschaft bereits in DictionaryBase vorhanden ist, wird der Wert ersetzt. Andernfalls wird ein neues Element erstellt. Im Gegensatz dazu ändert die Add-Methode keine vorhandenen Elemente.
Beispiel
[Visual Basic, C#, C++] Im folgenden Codebeispiel wird die DictionaryBase-Klasse implementiert und diese Implementierung zum Erstellen eines Wörterbuchs aus String-Schlüsseln und -Werten mit einer Length von höchstens 5 Zeichen verwendet.
Imports System
Imports System.Collections
Public Class ShortStringDictionary
Inherits DictionaryBase
Default Public Property Item(key As [String]) As [String]
Get
Return CType(Dictionary(key), [String])
End Get
Set
Dictionary(key) = value
End Set
End Property
Public ReadOnly Property Keys() As ICollection
Get
Return Dictionary.Keys
End Get
End Property
Public ReadOnly Property Values() As ICollection
Get
Return Dictionary.Values
End Get
End Property
Public Sub Add(key As [String], value As [String])
Dictionary.Add(key, value)
End Sub 'Add
Public Function Contains(key As [String]) As Boolean
Return Dictionary.Contains(key)
End Function 'Contains
Public Sub Remove(key As [String])
Dictionary.Remove(key)
End Sub 'Remove
Protected Overrides Sub OnInsert(key As [Object], value As [Object])
If Not key.GetType() Is Type.GetType("System.String") Then
Throw New ArgumentException("key must be of type String.", "key")
Else
Dim strKey As [String] = CType(key, [String])
If strKey.Length > 5 Then
Throw New ArgumentException("key must be no more than 5 characters in length.", "key")
End If
End If
If Not value.GetType() Is Type.GetType("System.String") Then
Throw New ArgumentException("value must be of type String.", "value")
Else
Dim strValue As [String] = CType(value, [String])
If strValue.Length > 5 Then
Throw New ArgumentException("value must be no more than 5 characters in length.", "value")
End If
End If
End Sub 'OnInsert
Protected Overrides Sub OnRemove(key As [Object], value As [Object])
If Not key.GetType() Is Type.GetType("System.String") Then
Throw New ArgumentException("key must be of type String.", "key")
Else
Dim strKey As [String] = CType(key, [String])
If strKey.Length > 5 Then
Throw New ArgumentException("key must be no more than 5 characters in length.", "key")
End If
End If
End Sub 'OnRemove
Protected Overrides Sub OnSet(key As [Object], oldValue As [Object], newValue As [Object])
If Not key.GetType() Is Type.GetType("System.String") Then
Throw New ArgumentException("key must be of type String.", "key")
Else
Dim strKey As [String] = CType(key, [String])
If strKey.Length > 5 Then
Throw New ArgumentException("key must be no more than 5 characters in length.", "key")
End If
End If
If Not newValue.GetType() Is Type.GetType("System.String") Then
Throw New ArgumentException("newValue must be of type String.", "newValue")
Else
Dim strValue As [String] = CType(newValue, [String])
If strValue.Length > 5 Then
Throw New ArgumentException("newValue must be no more than 5 characters in length.", "newValue")
End If
End If
End Sub 'OnSet
Protected Overrides Sub OnValidate(key As [Object], value As [Object])
If Not key.GetType() Is Type.GetType("System.String") Then
Throw New ArgumentException("key must be of type String.", "key")
Else
Dim strKey As [String] = CType(key, [String])
If strKey.Length > 5 Then
Throw New ArgumentException("key must be no more than 5 characters in length.", "key")
End If
End If
If Not value.GetType() Is Type.GetType("System.String") Then
Throw New ArgumentException("value must be of type String.", "value")
Else
Dim strValue As [String] = CType(value, [String])
If strValue.Length > 5 Then
Throw New ArgumentException("value must be no more than 5 characters in length.", "value")
End If
End If
End Sub 'OnValidate
End Class 'ShortStringDictionary
Public Class SamplesDictionaryBase
Public Shared Sub Main()
' Creates and initializes a new DictionaryBase.
Dim mySSC As New ShortStringDictionary()
' Adds elements to the collection.
mySSC.Add("One", "a")
mySSC.Add("Two", "ab")
mySSC.Add("Three", "abc")
mySSC.Add("Four", "abcd")
mySSC.Add("Five", "abcde")
' Tries to add a value that is too long.
Try
mySSC.Add("Ten", "abcdefghij")
Catch e As ArgumentException
Console.WriteLine(e.ToString())
End Try
' Tries to add a key that is too long.
Try
mySSC.Add("Eleven", "ijk")
Catch e As ArgumentException
Console.WriteLine(e.ToString())
End Try
Console.WriteLine()
' Displays the contents of the collection using the enumerator.
Console.WriteLine("Initial contents of the collection:")
PrintKeysAndValues(mySSC)
' Searches the collection with Contains.
Console.WriteLine("Contains ""Three"": {0}", mySSC.Contains("Three"))
Console.WriteLine("Contains ""Twelve"": {0}", mySSC.Contains("Twelve"))
Console.WriteLine()
' Removes an element from the collection.
mySSC.Remove("Two")
' Displays the contents of the collection using the Keys property.
Console.WriteLine("New state of the collection:")
PrintKeysAndValues3(mySSC)
End Sub 'Main
' Uses the enumerator.
Public Shared Sub PrintKeysAndValues(myCol As ShortStringDictionary)
Dim myDE As DictionaryEntry
Dim myEnumerator As System.Collections.IEnumerator = myCol.GetEnumerator()
While myEnumerator.MoveNext()
If Not (myEnumerator.Current Is Nothing) Then
myDE = CType(myEnumerator.Current, DictionaryEntry)
Console.WriteLine(" {0,-5} : {1}", myDE.Key, myDE.Value)
End If
End While
Console.WriteLine()
End Sub 'PrintKeysAndValues
' Uses the foreach statement which hides the complexity of the enumerator.
Public Shared Sub PrintKeysAndValues2(myCol As ShortStringDictionary)
Dim myDE As DictionaryEntry
For Each myDE In myCol
Console.WriteLine(" {0,-5} : {1}", myDE.Key, myDE.Value)
Next myDE
Console.WriteLine()
End Sub 'PrintKeysAndValues2
' Uses the Keys property and the Item property.
Public Shared Sub PrintKeysAndValues3(myCol As ShortStringDictionary)
Dim myKeys As ICollection = myCol.Keys
Dim k As [String]
For Each k In myKeys
Console.WriteLine(" {0,-5} : {1}", k, myCol(k))
Next k
Console.WriteLine()
End Sub 'PrintKeysAndValues3
End Class 'SamplesDictionaryBase
'This code produces the following output.
'
'System.ArgumentException: value must be no more than 5 characters in length.
'Parameter name: value
' at ShortStringDictionary.OnValidate(Object key, Object value)
' at System.Collections.DictionaryBase.System.Collections.IDictionary.Add(Object key, Object value)
' at SamplesDictionaryBase.Main()
'System.ArgumentException: key must be no more than 5 characters in length.
'Parameter name: key
' at ShortStringDictionary.OnValidate(Object key, Object value)
' at System.Collections.DictionaryBase.System.Collections.IDictionary.Add(Object key, Object value)
' at SamplesDictionaryBase.Main()
'
'Initial contents of the collection:
' One : a
' Four : abcd
' Three : abc
' Two : ab
' Five : abcde
'
'Contains "Three": True
'Contains "Twelve": False
'
'New state of the collection:
' One : a
' Four : abcd
' Three : abc
' Five : abcde
[C#]
using System;
using System.Collections;
public class ShortStringDictionary : DictionaryBase {
public String this[ String key ] {
get {
return( (String) Dictionary[key] );
}
set {
Dictionary[key] = value;
}
}
public ICollection Keys {
get {
return( Dictionary.Keys );
}
}
public ICollection Values {
get {
return( Dictionary.Values );
}
}
public void Add( String key, String value ) {
Dictionary.Add( key, value );
}
public bool Contains( String key ) {
return( Dictionary.Contains( key ) );
}
public void Remove( String key ) {
Dictionary.Remove( key );
}
protected override void OnInsert( Object key, Object value ) {
if ( key.GetType() != Type.GetType("System.String") )
throw new ArgumentException( "key must be of type String.", "key" );
else {
String strKey = (String) key;
if ( strKey.Length > 5 )
throw new ArgumentException( "key must be no more than 5 characters in length.", "key" );
}
if ( value.GetType() != Type.GetType("System.String") )
throw new ArgumentException( "value must be of type String.", "value" );
else {
String strValue = (String) value;
if ( strValue.Length > 5 )
throw new ArgumentException( "value must be no more than 5 characters in length.", "value" );
}
}
protected override void OnRemove( Object key, Object value ) {
if ( key.GetType() != Type.GetType("System.String") )
throw new ArgumentException( "key must be of type String.", "key" );
else {
String strKey = (String) key;
if ( strKey.Length > 5 )
throw new ArgumentException( "key must be no more than 5 characters in length.", "key" );
}
}
protected override void OnSet( Object key, Object oldValue, Object newValue ) {
if ( key.GetType() != Type.GetType("System.String") )
throw new ArgumentException( "key must be of type String.", "key" );
else {
String strKey = (String) key;
if ( strKey.Length > 5 )
throw new ArgumentException( "key must be no more than 5 characters in length.", "key" );
}
if ( newValue.GetType() != Type.GetType("System.String") )
throw new ArgumentException( "newValue must be of type String.", "newValue" );
else {
String strValue = (String) newValue;
if ( strValue.Length > 5 )
throw new ArgumentException( "newValue must be no more than 5 characters in length.", "newValue" );
}
}
protected override void OnValidate( Object key, Object value ) {
if ( key.GetType() != Type.GetType("System.String") )
throw new ArgumentException( "key must be of type String.", "key" );
else {
String strKey = (String) key;
if ( strKey.Length > 5 )
throw new ArgumentException( "key must be no more than 5 characters in length.", "key" );
}
if ( value.GetType() != Type.GetType("System.String") )
throw new ArgumentException( "value must be of type String.", "value" );
else {
String strValue = (String) value;
if ( strValue.Length > 5 )
throw new ArgumentException( "value must be no more than 5 characters in length.", "value" );
}
}
}
public class SamplesDictionaryBase {
public static void Main() {
// Creates and initializes a new DictionaryBase.
ShortStringDictionary mySSC = new ShortStringDictionary();
// Adds elements to the collection.
mySSC.Add( "One", "a" );
mySSC.Add( "Two", "ab" );
mySSC.Add( "Three", "abc" );
mySSC.Add( "Four", "abcd" );
mySSC.Add( "Five", "abcde" );
// Tries to add a value that is too long.
try {
mySSC.Add( "Ten", "abcdefghij" );
}
catch ( ArgumentException e ) {
Console.WriteLine( e.ToString() );
}
// Tries to add a key that is too long.
try {
mySSC.Add( "Eleven", "ijk" );
}
catch ( ArgumentException e ) {
Console.WriteLine( e.ToString() );
}
Console.WriteLine();
// Displays the contents of the collection using the enumerator.
Console.WriteLine( "Initial contents of the collection:" );
PrintKeysAndValues( mySSC );
// Searches the collection with Contains.
Console.WriteLine( "Contains \"Three\": {0}", mySSC.Contains( "Three" ) );
Console.WriteLine( "Contains \"Twelve\": {0}", mySSC.Contains( "Twelve" ) );
Console.WriteLine();
// Removes an element from the collection.
mySSC.Remove( "Two" );
// Displays the contents of the collection using the Keys property.
Console.WriteLine( "New state of the collection:" );
PrintKeysAndValues3( mySSC );
}
// Uses the enumerator.
public static void PrintKeysAndValues( ShortStringDictionary myCol ) {
DictionaryEntry myDE;
System.Collections.IEnumerator myEnumerator = myCol.GetEnumerator();
while ( myEnumerator.MoveNext() )
if ( myEnumerator.Current != null ) {
myDE = (DictionaryEntry) myEnumerator.Current;
Console.WriteLine( " {0,-5} : {1}", myDE.Key, myDE.Value );
}
Console.WriteLine();
}
// Uses the foreach statement which hides the complexity of the enumerator.
public static void PrintKeysAndValues2( ShortStringDictionary myCol ) {
foreach ( DictionaryEntry myDE in myCol )
Console.WriteLine( " {0,-5} : {1}", myDE.Key, myDE.Value );
Console.WriteLine();
}
// Uses the Keys property and the Item property.
public static void PrintKeysAndValues3( ShortStringDictionary myCol ) {
ICollection myKeys = myCol.Keys;
foreach ( String k in myKeys )
Console.WriteLine( " {0,-5} : {1}", k, myCol[k] );
Console.WriteLine();
}
}
/*
This code produces the following output.
System.ArgumentException: value must be no more than 5 characters in length.
Parameter name: value
at ShortStringDictionary.OnValidate(Object key, Object value)
at System.Collections.DictionaryBase.System.Collections.IDictionary.Add(Object key, Object value)
at SamplesDictionaryBase.Main()
System.ArgumentException: key must be no more than 5 characters in length.
Parameter name: key
at ShortStringDictionary.OnValidate(Object key, Object value)
at System.Collections.DictionaryBase.System.Collections.IDictionary.Add(Object key, Object value)
at SamplesDictionaryBase.Main()
Initial contents of the collection:
One : a
Four : abcd
Three : abc
Two : ab
Five : abcde
Contains "Three": True
Contains "Twelve": False
New state of the collection:
One : a
Four : abcd
Three : abc
Five : abcde
*/
[C++]
#using <mscorlib.dll>
using namespace System;
using namespace System::Collections;
public __gc class ShortStringDictionary : public DictionaryBase
{
public:
__property String* get_Item( String* key )
{
return __try_cast<String*>(Dictionary->Item[key]);
}
__property void set_Item( String* key, String* value )
{
Dictionary->Item[key] = value;
}
__property ICollection* get_Keys()
{
return(Dictionary->Keys);
}
__property ICollection* get_Values()
{
return(Dictionary->Values);
}
void Add(String* key, String* value) {
Dictionary->Add(key, value);
}
bool Contains(String* key) {
return(Dictionary->Contains(key));
}
void Remove(String* key) {
Dictionary->Remove(key);
}
protected:
void OnInsert(Object* key, Object* value) {
if (key->GetType() != Type::GetType(S"System.String"))
throw new ArgumentException(S"key must be of type String.", S"key");
else {
String* strKey = __try_cast<String*>(key);
if (strKey->Length > 5)
throw new ArgumentException(S"key must be no more than 5 characters in length.", S"key");
}
if (value->GetType() != Type::GetType(S"System.String"))
throw new ArgumentException(S"value must be of type String.", S"value");
else {
String* strValue = __try_cast<String*>(value);
if (strValue->Length > 5)
throw new ArgumentException(S"value must be no more than 5 characters in length.", S"value");
}
}
void OnRemove(Object* key, Object* value) {
if (key->GetType() != Type::GetType(S"System.String"))
throw new ArgumentException(S"key must be of type String.", S"key");
else {
String* strKey = __try_cast<String*>(key);
if (strKey->Length > 5)
throw new ArgumentException(S"key must be no more than 5 characters in length.", S"key");
}
}
void OnSet(Object* key, Object* oldValue, Object* newValue) {
if (key->GetType() != Type::GetType(S"System.String"))
throw new ArgumentException(S"key must be of type String.", S"key");
else {
String* strKey = __try_cast<String*>(key);
if (strKey->Length > 5)
throw new ArgumentException(S"key must be no more than 5 characters in length.", S"key");
}
if (newValue->GetType() != Type::GetType(S"System.String"))
throw new ArgumentException(S"newValue must be of type String.", S"newValue");
else {
String* strValue = __try_cast<String*>(newValue);
if (strValue->Length > 5)
throw new ArgumentException(S"newValue must be no more than 5 characters in length.", S"newValue");
}
}
void OnValidate(Object* key, Object* value) {
if (key->GetType() != Type::GetType(S"System.String"))
throw new ArgumentException(S"key must be of type String.", S"key");
else
{
String* strKey = __try_cast<String*>(key);
if (strKey->Length > 5)
throw new ArgumentException(S"key must be no more than 5 characters in length.", S"key");
}
if (value->GetType() != Type::GetType(S"System.String"))
throw new ArgumentException(S"value must be of type String.", S"value");
else
{
String* strValue = __try_cast<String*>(value);
if (strValue->Length > 5)
throw new ArgumentException(S"value must be no more than 5 characters in length.", S"value");
}
}
};
// Uses the enumerator.
void PrintKeysAndValues(ShortStringDictionary* myCol)
{
DictionaryEntry* myDE;
System::Collections::IEnumerator* myEnumerator = myCol->GetEnumerator();
while (myEnumerator->MoveNext())
if (myEnumerator->Current != 0)
{
myDE = __try_cast<DictionaryEntry*>(myEnumerator->Current);
Console::WriteLine(S" {0, -5} : {1}", myDE->Key, myDE->Value);
}
Console::WriteLine();
}
// Uses the foreach statement which hides the complexity of the enumerator.
void PrintKeysAndValues2(ShortStringDictionary* myCol)
{
IEnumerator* myEnum = myCol->GetEnumerator();
while (myEnum->MoveNext())
{
DictionaryEntry* myDE = __try_cast<DictionaryEntry*>(myEnum->Current);
Console::WriteLine(S" {0, -5} : {1}", myDE->Key, myDE->Value);
Console::WriteLine();
}
}
// Uses the Keys property and the Item property.
void PrintKeysAndValues3(ShortStringDictionary* myCol)
{
ICollection* myKeys = myCol->Keys;
IEnumerator* myEnum = myKeys->GetEnumerator();
while (myEnum->MoveNext())
{
String* k = __try_cast<String*>(myEnum->Current);
Console::WriteLine(S" {0, -5} : {1}", k, myCol->Item[k]);
Console::WriteLine();
}
}
int main()
{
// Creates and initializes a new DictionaryBase.
ShortStringDictionary* mySSC = new ShortStringDictionary();
// Adds elements to the collection.
mySSC->Add(S"One", S"a");
mySSC->Add(S"Two", S"ab");
mySSC->Add(S"Three", S"abc");
mySSC->Add(S"Four", S"abcd");
mySSC->Add(S"Five", S"abcde");
// Tries to add a value that is too long.
try
{
mySSC->Add(S"Ten", S"abcdefghij");
}
catch (ArgumentException* e)
{
Console::WriteLine(e);
}
// Tries to add a key that is too long.
try
{
mySSC->Add(S"Eleven", S"ijk");
}
catch (ArgumentException* e)
{
Console::WriteLine(e);
}
Console::WriteLine();
// Displays the contents of the collection using the enumerator.
Console::WriteLine(S"Initial contents of the collection:");
PrintKeysAndValues(mySSC);
// Searches the collection with Contains.
Console::WriteLine(S"Contains \"Three\": {0}", __box(mySSC->Contains(S"Three")));
Console::WriteLine(S"Contains \"Twelve\": {0}", __box(mySSC->Contains(S"Twelve")));
Console::WriteLine();
// Removes an element from the collection.
mySSC->Remove(S"Two");
// Displays the contents of the collection using the Keys property.
Console::WriteLine(S"New state of the collection:");
PrintKeysAndValues3(mySSC);
}
/*
This code produces the following output.
System::ArgumentException: value must be no more than 5 characters in length.
Parameter name: value
at ShortStringDictionary::OnValidate(Object key, Object value)
at System::Collections::DictionaryBase::System.Collections::IDictionary*.Add(Object key, Object value)
at SamplesDictionaryBase::Main()
System::ArgumentException: key must be no more than 5 characters in length.
Parameter name: key
at ShortStringDictionary::OnValidate(Object key, Object value)
at System::Collections::DictionaryBase::System.Collections::IDictionary*.Add(Object key, Object value)
at SamplesDictionaryBase::Main()
Initial contents of the collection:
One : a
Four : abcd
Three : abc
Two : ab
Five : abcde
Contains S"Three": True
Contains S"Twelve": False
New state of the collection:
One : a
Four : abcd
Three : abc
Five : abcde
*/
[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
DictionaryBase-Klasse | DictionaryBase-Member | System.Collections-Namespace | Add