NameObjectCollectionBase.IsReadOnly-Eigenschaft
Ruft einen Wert ab, der angibt, ob die NameObjectCollectionBase-Instanz schreibgeschützt ist, oder legt diesen fest.
Namespace: System.Collections.Specialized
Assembly: System (in system.dll)
Syntax
'Declaration
Protected Property IsReadOnly As Boolean
'Usage
Dim value As Boolean
value = Me.IsReadOnly
Me.IsReadOnly = value
protected bool IsReadOnly { get; set; }
protected:
property bool IsReadOnly {
bool get ();
void set (bool value);
}
/** @property */
protected boolean get_IsReadOnly ()
/** @property */
protected void set_IsReadOnly (boolean value)
protected function get IsReadOnly () : boolean
protected function set IsReadOnly (value : boolean)
Eigenschaftenwert
true, wenn die NameObjectCollectionBase-Instanz schreibgeschützt ist, andernfalls false.
Hinweise
Eine schreibgeschützte Auflistung gestattet nach dem Erstellen der Auflistung weder das Hinzufügen noch das Ändern oder Entfernen von Elementen.
Eine schreibgeschützte Auflistung ist eine Auflistung mit einem Wrapper, der das Ändern der Auflistung verhindert. Daher werden Änderungen an der zugrunde liegenden Auflistung auch in der schreibgeschützten Auflistung dargestellt.
Das Abrufen des Werts dieser Eigenschaft ist eine O(1)-Operation.
Beispiel
Im folgenden Codebeispiel wird eine schreibgeschützte Auflistung erstellt.
Imports System
Imports System.Collections
Imports System.Collections.Specialized
Public Class MyCollection
Inherits NameObjectCollectionBase
Private _de As New DictionaryEntry()
' Gets a key-and-value pair (DictionaryEntry) using an index.
Default Public ReadOnly Property Item(index As Integer) As DictionaryEntry
Get
_de.Key = Me.BaseGetKey(index)
_de.Value = Me.BaseGet(index)
Return _de
End Get
End Property
' Adds elements from an IDictionary into the new collection.
Public Sub New(d As IDictionary, bReadOnly As [Boolean])
Dim de As DictionaryEntry
For Each de In d
Me.BaseAdd(CType(de.Key, [String]), de.Value)
Next de
Me.IsReadOnly = bReadOnly
End Sub 'New
' Adds an entry to the collection.
Public Sub Add(key As [String], value As [Object])
Me.BaseAdd(key, value)
End Sub 'Add
End Class 'MyCollection
Public Class SamplesNameObjectCollectionBase
Public Shared Sub Main()
' Creates and initializes a new MyCollection that is read-only.
Dim d = New ListDictionary()
d.Add("red", "apple")
d.Add("yellow", "banana")
d.Add("green", "pear")
Dim myROCol As New MyCollection(d, True)
' Tries to add a new item.
Try
myROCol.Add("blue", "sky")
Catch e As NotSupportedException
Console.WriteLine(e.ToString())
End Try
' Displays the keys and values of the MyCollection.
Console.WriteLine("Read-Only Collection:")
PrintKeysAndValues(myROCol)
End Sub 'Main
Public Shared Sub PrintKeysAndValues(myCol As MyCollection)
Dim i As Integer
For i = 0 To myCol.Count - 1
Console.WriteLine("[{0}] : {1}, {2}", i, myCol(i).Key, myCol(i).Value)
Next i
End Sub 'PrintKeysAndValues
End Class 'SamplesNameObjectCollectionBase
'This code produces the following output.
'
'System.NotSupportedException: Collection is read-only.
' at System.Collections.Specialized.NameObjectCollectionBase.BaseAdd(String name, Object value)
' at SamplesNameObjectCollectionBase.Main()
'Read-Only Collection:
'[0] : red, apple
'[1] : yellow, banana
'[2] : green, pear
using System;
using System.Collections;
using System.Collections.Specialized;
public class MyCollection : NameObjectCollectionBase {
private DictionaryEntry _de = new DictionaryEntry();
// Gets a key-and-value pair (DictionaryEntry) using an index.
public DictionaryEntry this[ int index ] {
get {
_de.Key = this.BaseGetKey( index );
_de.Value = this.BaseGet( index );
return( _de );
}
}
// Adds elements from an IDictionary into the new collection.
public MyCollection( IDictionary d, Boolean bReadOnly ) {
foreach ( DictionaryEntry de in d ) {
this.BaseAdd( (String) de.Key, de.Value );
}
this.IsReadOnly = bReadOnly;
}
// Adds an entry to the collection.
public void Add( String key, Object value ) {
this.BaseAdd( key, value );
}
}
public class SamplesNameObjectCollectionBase {
public static void Main() {
// Creates and initializes a new MyCollection that is read-only.
IDictionary d = new ListDictionary();
d.Add( "red", "apple" );
d.Add( "yellow", "banana" );
d.Add( "green", "pear" );
MyCollection myROCol = new MyCollection( d, true );
// Tries to add a new item.
try {
myROCol.Add( "blue", "sky" );
}
catch ( NotSupportedException e ) {
Console.WriteLine( e.ToString() );
}
// Displays the keys and values of the MyCollection.
Console.WriteLine( "Read-Only Collection:" );
PrintKeysAndValues( myROCol );
}
public static void PrintKeysAndValues( MyCollection myCol ) {
for ( int i = 0; i < myCol.Count; i++ ) {
Console.WriteLine( "[{0}] : {1}, {2}", i, myCol[i].Key, myCol[i].Value );
}
}
}
/*
This code produces the following output.
System.NotSupportedException: Collection is read-only.
at System.Collections.Specialized.NameObjectCollectionBase.BaseAdd(String name, Object value)
at SamplesNameObjectCollectionBase.Main()
Read-Only Collection:
[0] : red, apple
[1] : yellow, banana
[2] : green, pear
*/
#using <System.dll>
using namespace System;
using namespace System::Collections;
using namespace System::Collections::Specialized;
public ref class MyCollection : public NameObjectCollectionBase {
private:
DictionaryEntry^ _de;
// Gets a key-and-value pair (DictionaryEntry) using an index.
public:
property DictionaryEntry^ default[ int ] {
DictionaryEntry^ get( int index ) {
_de->Key = this->BaseGetKey( index );
_de->Value = this->BaseGet( index );
return( _de );
}
}
// Adds elements from an IDictionary into the new collection.
MyCollection( IDictionary^ d, Boolean bReadOnly ) {
_de = gcnew DictionaryEntry();
for each ( DictionaryEntry^ de in d ) {
this->BaseAdd( (String^) de->Key, de->Value );
}
this->IsReadOnly = bReadOnly;
}
// Adds an entry to the collection.
void Add( String^ key, Object^ value ) {
this->BaseAdd( key, value );
}
};
public ref class SamplesNameObjectCollectionBase {
public:
static void Main() {
// Creates and initializes a new MyCollection that is read-only.
IDictionary^ d = gcnew ListDictionary();
d->Add( "red", "apple" );
d->Add( "yellow", "banana" );
d->Add( "green", "pear" );
MyCollection^ myROCol = gcnew MyCollection( d, true );
// Tries to add a new item.
try {
myROCol->Add( "blue", "sky" );
}
catch ( NotSupportedException^ e ) {
Console::WriteLine( e->ToString() );
}
// Displays the keys and values of the MyCollection.
Console::WriteLine( "Read-Only Collection:" );
PrintKeysAndValues( myROCol );
}
static void PrintKeysAndValues( MyCollection^ myCol ) {
for ( int i = 0; i < myCol->Count; i++ ) {
Console::WriteLine( "[{0}] : {1}, {2}", i, myCol[i]->Key, myCol[i]->Value );
}
}
};
int main()
{
SamplesNameObjectCollectionBase::Main();
}
/*
This code produces the following output.
System.NotSupportedException: Collection is read-only.
at System.Collections.Specialized.NameObjectCollectionBase.BaseAdd(String name, Object value)
at SamplesNameObjectCollectionBase.Main()
Read-Only Collection:
[0] : red, apple
[1] : yellow, banana
[2] : green, pear
*/
import System.* ;
import System.Collections.* ;
import System.Collections.Specialized.* ;
public class MyCollection extends NameObjectCollectionBase
{
private DictionaryEntry _de = new DictionaryEntry();
// Gets a key-and-value pair (DictionaryEntry) using an index.
/** @property
*/
public DictionaryEntry get_Item(int index)
{
_de.set_Key(this.BaseGetKey(index));
_de.set_Value(this.BaseGet(index));
return _de ;
} //get_Item
// Adds elements from an IDictionary into the new collection.
public MyCollection(IDictionary d, boolean bReadOnly)
{
IDictionaryEnumerator objEnum = d.GetEnumerator();
while (objEnum.MoveNext()) {
DictionaryEntry de = (DictionaryEntry)objEnum.get_Current();
this.BaseAdd(((String)(de.get_Key())), de.get_Value());
}
this.set_IsReadOnly(bReadOnly);
} //MyCollection
// Adds an entry to the collection.
public void Add(String key, Object value)
{
this.BaseAdd(key, value);
} //Add
} //MyCollection
public class SamplesNameObjectCollectionBase
{
public static void main(String[] args)
{
// Creates and initializes a new MyCollection that is read-only.
IDictionary d = new ListDictionary();
d.Add("red", "apple");
d.Add("yellow", "banana");
d.Add("green", "pear");
MyCollection myROCol = new MyCollection(d,true);
// Tries to add a new item.
try {
myROCol.Add("blue", "sky");
}
catch(NotSupportedException e) {
Console.WriteLine(e.ToString());
}
// Displays the keys and values of the MyCollection.
Console.WriteLine("Read-Only Collection:");
PrintKeysAndValues(myROCol);
} //main
public static void PrintKeysAndValues(MyCollection myCol)
{
for(int i=0;i < myCol.get_Count(); i++) {
Console.WriteLine("[{0}] : {1}, {2}",System.Convert.ToString(i),
myCol.get_Item(i).get_Key(), myCol.get_Item(i).get_Value());
}
} //PrintKeysAndValues
} //SamplesNameObjectCollectionBase
/*
This code produces the following output.
System.NotSupportedException: Collection is read-only.
at System.Collections.Specialized.NameObjectCollectionBase.BaseAdd(
String name, Object value)
at SamplesNameObjectCollectionBase.main(String[] args)
Read-Only Collection:
[0] : red, apple
[1] : yellow, banana
[2] : green, pear
*/
Plattformen
Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile für Pocket PC, Windows Mobile für Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
.NET Framework unterstützt nicht alle Versionen sämtlicher Plattformen. Eine Liste der unterstützten Versionen finden Sie unter Systemanforderungen.
Versionsinformationen
.NET Framework
Unterstützt in: 2.0, 1.1, 1.0
.NET Compact Framework
Unterstützt in: 2.0, 1.0
Siehe auch
Referenz
NameObjectCollectionBase-Klasse
NameObjectCollectionBase-Member
System.Collections.Specialized-Namespace