ArrayList.IsFixedSize Eigenschap
Definitie
Belangrijk
Bepaalde informatie heeft betrekking op een voorlopige productversie die aanzienlijk kan worden gewijzigd voordat deze wordt uitgebracht. Microsoft biedt geen enkele expliciete of impliciete garanties met betrekking tot de informatie die hier wordt verstrekt.
Hiermee wordt een waarde opgehaald die aangeeft of de grootte van een ArrayList vaste grootte is.
public:
virtual property bool IsFixedSize { bool get(); };public virtual bool IsFixedSize { get; }member this.IsFixedSize : boolPublic Overridable ReadOnly Property IsFixedSize As BooleanWaarde van eigenschap
true als het ArrayList een vaste grootte heeft; falseanders . De standaardwaarde is false.
Implementeringen
Voorbeelden
In het volgende codevoorbeeld ziet u hoe u een wrapper met een vaste grootte rond een ArrayList.
using System;
using System.Collections;
public class SamplesArrayList {
public static void Main() {
// Creates and initializes a new ArrayList.
ArrayList myAL = new ArrayList();
myAL.Add( "The" );
myAL.Add( "quick" );
myAL.Add( "brown" );
myAL.Add( "fox" );
myAL.Add( "jumps" );
myAL.Add( "over" );
myAL.Add( "the" );
myAL.Add( "lazy" );
myAL.Add( "dog" );
// Create a fixed-size wrapper around the ArrayList.
ArrayList myFixedSizeAL = ArrayList.FixedSize( myAL );
// Display whether the ArrayLists have a fixed size or not.
Console.WriteLine( "myAL {0}.", myAL.IsFixedSize ? "has a fixed size" : "does not have a fixed size" );
Console.WriteLine( "myFixedSizeAL {0}.", myFixedSizeAL.IsFixedSize ? "has a fixed size" : "does not have a fixed size" );
Console.WriteLine();
// Display both ArrayLists.
Console.WriteLine( "Initially," );
Console.Write( "Standard :" );
PrintValues( myAL, ' ' );
Console.Write( "Fixed size:" );
PrintValues( myFixedSizeAL, ' ' );
// Sort is allowed in the fixed-size ArrayList.
myFixedSizeAL.Sort();
// Display both ArrayLists.
Console.WriteLine( "After Sort," );
Console.Write( "Standard :" );
PrintValues( myAL, ' ' );
Console.Write( "Fixed size:" );
PrintValues( myFixedSizeAL, ' ' );
// Reverse is allowed in the fixed-size ArrayList.
myFixedSizeAL.Reverse();
// Display both ArrayLists.
Console.WriteLine( "After Reverse," );
Console.Write( "Standard :" );
PrintValues( myAL, ' ' );
Console.Write( "Fixed size:" );
PrintValues( myFixedSizeAL, ' ' );
// Add an element to the standard ArrayList.
myAL.Add( "AddMe" );
// Display both ArrayLists.
Console.WriteLine( "After adding to the standard ArrayList," );
Console.Write( "Standard :" );
PrintValues( myAL, ' ' );
Console.Write( "Fixed size:" );
PrintValues( myFixedSizeAL, ' ' );
Console.WriteLine();
// Adding or inserting elements to the fixed-size ArrayList throws an exception.
try {
myFixedSizeAL.Add( "AddMe2" );
} catch ( Exception myException ) {
Console.WriteLine("Exception: " + myException.ToString());
}
try {
myFixedSizeAL.Insert( 3, "InsertMe" );
} catch ( Exception myException ) {
Console.WriteLine("Exception: " + myException.ToString());
}
}
public static void PrintValues( IEnumerable myList, char mySeparator ) {
foreach ( Object obj in myList )
Console.Write( "{0}{1}", mySeparator, obj );
Console.WriteLine();
}
}
/*
This code produces the following output.
myAL does not have a fixed size.
myFixedSizeAL has a fixed size.
Initially,
Standard : The quick brown fox jumps over the lazy dog
Fixed size: The quick brown fox jumps over the lazy dog
After Sort,
Standard : brown dog fox jumps lazy over quick the The
Fixed size: brown dog fox jumps lazy over quick the The
After Reverse,
Standard : The the quick over lazy jumps fox dog brown
Fixed size: The the quick over lazy jumps fox dog brown
After adding to the standard ArrayList,
Standard : The the quick over lazy jumps fox dog brown AddMe
Fixed size: The the quick over lazy jumps fox dog brown AddMe
Exception: System.NotSupportedException: Collection was of a fixed size.
at System.Collections.FixedSizeArrayList.Add(Object obj)
at SamplesArrayList.Main()
Exception: System.NotSupportedException: Collection was of a fixed size.
at System.Collections.FixedSizeArrayList.Insert(int index, Object obj)
at SamplesArrayList.Main()
*/
Imports System.Collections
Public Class SamplesArrayList
Public Shared Sub Main()
' Creates and initializes a new ArrayList.
Dim myAL As New ArrayList()
myAL.Add("The")
myAL.Add("quick")
myAL.Add("brown")
myAL.Add("fox")
myAL.Add("jumps")
myAL.Add("over")
myAL.Add("the")
myAL.Add("lazy")
myAL.Add("dog")
' Create a fixed-size wrapper around the ArrayList.
Dim myFixedSizeAL As ArrayList = ArrayList.FixedSize(myAL)
' Display whether the ArrayLists have a fixed size or not.
Dim msg As String
If myAL.IsFixedSize Then
msg = "has a fixed size"
Else
msg = "does not have a fixed size"
End If
Console.WriteLine("myAL {0}.", msg)
If myFixedSizeAL.IsFixedSize Then
msg = "has a fixed size"
Else
msg = "does not have a fixed size"
End If
Console.WriteLine("myFixedSizeAL {0}.", msg)
Console.WriteLine()
' Display both ArrayLists.
Console.WriteLine("Initially,")
Console.Write("Standard :")
PrintValues(myAL, " "c)
Console.Write("Fixed size:")
PrintValues(myFixedSizeAL, " "c)
' Sort is allowed in the fixed-size ArrayList.
myFixedSizeAL.Sort()
' Display both ArrayLists.
Console.WriteLine("After Sort,")
Console.Write("Standard :")
PrintValues(myAL, " "c)
Console.Write("Fixed size:")
PrintValues(myFixedSizeAL, " "c)
' Reverse is allowed in the fixed-size ArrayList.
myFixedSizeAL.Reverse()
' Display both ArrayLists.
Console.WriteLine("After Reverse,")
Console.Write("Standard :")
PrintValues(myAL, " "c)
Console.Write("Fixed size:")
PrintValues(myFixedSizeAL, " "c)
' Add an element to the standard ArrayList.
myAL.Add("AddMe")
' Display both ArrayLists.
Console.WriteLine("After adding to the standard ArrayList,")
Console.Write("Standard :")
PrintValues(myAL, " "c)
Console.Write("Fixed size:")
PrintValues(myFixedSizeAL, " "c)
Console.WriteLine()
' Adding or inserting elements to the fixed-size ArrayList throws an exception.
Try
myFixedSizeAL.Add("AddMe2")
Catch myException As Exception
Console.WriteLine("Exception: " + myException.ToString())
End Try
Try
myFixedSizeAL.Insert(3, "InsertMe")
Catch myException As Exception
Console.WriteLine("Exception: " + myException.ToString())
End Try
End Sub
Public Shared Sub PrintValues(myList As IEnumerable, mySeparator As Char)
Dim obj As [Object]
For Each obj In myList
Console.Write("{0}{1}", mySeparator, obj)
Next obj
Console.WriteLine()
End Sub
End Class
' This code produces the following output.
'
' myAL does not have a fixed size.
' myFixedSizeAL has a fixed size.
'
' Initially,
' Standard : The quick brown fox jumps over the lazy dog
' Fixed size: The quick brown fox jumps over the lazy dog
' After Sort,
' Standard : brown dog fox jumps lazy over quick the The
' Fixed size: brown dog fox jumps lazy over quick the The
' After Reverse,
' Standard : The the quick over lazy jumps fox dog brown
' Fixed size: The the quick over lazy jumps fox dog brown
' After adding to the standard ArrayList,
' Standard : The the quick over lazy jumps fox dog brown AddMe
' Fixed size: The the quick over lazy jumps fox dog brown AddMe
'
' Exception: System.NotSupportedException: Collection was of a fixed size.
' at System.Collections.FixedSizeArrayList.Add(Object obj)
' at SamplesArrayList.Main()
' Exception: System.NotSupportedException: Collection was of a fixed size.
' at System.Collections.FixedSizeArrayList.Insert(Int32 index, Object obj)
' at SamplesArrayList.Main()
Opmerkingen
Een verzameling met een vaste grootte staat het toevoegen of verwijderen van elementen na het maken van de verzameling niet toe, maar staat het wijzigen van bestaande elementen toe.
Een verzameling met een vaste grootte is gewoon een verzameling met een wrapper die voorkomt dat elementen worden toegevoegd en verwijderd; Als er dus wijzigingen worden aangebracht in de onderliggende verzameling, met inbegrip van het toevoegen of verwijderen van elementen, weerspiegelt de verzameling met vaste grootte deze wijzigingen.
Het ophalen van de waarde van deze eigenschap is een O(1) bewerking.
