Hashtable-Konstruktor (IHashCodeProvider, IComparer)
HINWEIS: Dieser Konstruktor ist mittlerweile veraltet.
Initialisiert eine neue leere Instanz der Hashtable-Klasse unter Verwendung der anfänglichen Standardkapazität, des Standardlastfaktors, des angegebenen Hashcodeanbieters und des angegebenen Comparers.
Namespace: System.Collections
Assembly: mscorlib (in mscorlib.dll)
Syntax
'Declaration
<ObsoleteAttribute("Please use Hashtable(IEqualityComparer) instead.")> _
Public Sub New ( _
hcp As IHashCodeProvider, _
comparer As IComparer _
)
'Usage
Dim hcp As IHashCodeProvider
Dim comparer As IComparer
Dim instance As New Hashtable(hcp, comparer)
[ObsoleteAttribute("Please use Hashtable(IEqualityComparer) instead.")]
public Hashtable (
IHashCodeProvider hcp,
IComparer comparer
)
[ObsoleteAttribute(L"Please use Hashtable(IEqualityComparer) instead.")]
public:
Hashtable (
IHashCodeProvider^ hcp,
IComparer^ comparer
)
/** @attribute ObsoleteAttribute("Please use Hashtable(IEqualityComparer) instead.") */
public Hashtable (
IHashCodeProvider hcp,
IComparer comparer
)
ObsoleteAttribute("Please use Hashtable(IEqualityComparer) instead.")
public function Hashtable (
hcp : IHashCodeProvider,
comparer : IComparer
)
Parameter
hcp
Das IHashCodeProvider-Objekt, das die Hashcodes für alle Schlüssel im Hashtable-Objekt bereitstellt.– oder –
NULL (Nothing in Visual Basic), wenn der Hashcode-Standardanbieter verwendet werden soll. Dies ist die jeweilige Object.GetHashCode-Implementierung eines Schlüssels.
comparer
Das IComparer-Objekt, mit dem ermittelt wird, ob zwei Schlüssel gleich sind.– oder –
NULL (Nothing in Visual Basic), wenn der Standardcomparer verwendet werden soll. Dies ist die jeweilige Object.Equals-Implementierung eines Schlüssels.
Hinweise
Anhand der Kapazität einer Hashtabelle wird die optimale Anzahl der Buckets für die Hashtabelle in Abhängigkeit vom Lastfaktor berechnet. Die Kapazität wird nach Bedarf automatisch erhöht.
Der Lastfaktor ist das maximale Verhältnis von Elementen zu Buckets. Ein kleinerer Lastfaktor führt zu einer schnelleren Suche bei höherem Speicherbedarf.
Wenn der tatsächliche Lastfaktor den angegebenen Lastfaktor erreicht, wird die Anzahl der Buckets automatisch auf die kleinste Primzahl erhöht, die größer als die doppelte Anzahl der derzeit vorhandenen Buckets ist.
Der Hashcodeanbieter verteilt Hashcodes für Schlüssel im Hashtable-Objekt. Der Hashcode-Standardanbieter ist die Object.GetHashCode-Implementierung des Schlüssels.
Der Comparer ermittelt, ob zwei Schlüssel gleich sind. Jeder Schlüssel in einer Hashtable muss eindeutig sein. Der Standardcomparer ist die Object.Equals-Implementierung des Schlüssels.
Benutzerdefinierte Hashcodeanbieter und Comparer ermöglichen Szenarien wie das Durchführen einer Suche ohne Berücksichtigung der Groß- und Kleinschreibung in Zeichenfolgen.
Bei diesem Konstruktor handelt es sich um eine O(1)-Operation.
Beispiel
Im folgenden Codebeispiel werden Hashtabellen mit verschiedenen Hashtable-Konstruktoren erstellt und die Unterschiede im Verhalten der Hashtabellen dargestellt, auch dann, wenn jede Tabelle dieselben Elemente enthält.
Imports System
Imports System.Collections
Imports System.Globalization
Public Class myComparer
Implements IEqualityComparer
Public Function Equals1(ByVal x As Object, ByVal y As Object) _
As Boolean Implements IEqualityComparer.Equals
Return x.Equals(y)
End Function
Public Function GetHashCode1(ByVal obj As Object) _
As Integer Implements IEqualityComparer.GetHashCode
Return obj.ToString().ToLower().GetHashCode()
End Function
End Class
Public Class myCultureComparer
Implements IEqualityComparer
Dim myComparer As CaseInsensitiveComparer
Public Sub New()
myComparer = CaseInsensitiveComparer.DefaultInvariant
End Sub
Public Sub New(ByVal myCulture As CultureInfo)
myComparer = New CaseInsensitiveComparer(myCulture)
End Sub
Public Function Equals1(ByVal x As Object, ByVal y As Object) _
As Boolean Implements IEqualityComparer.Equals
If (myComparer.Compare(x, y) = 0) Then
Return True
Else
Return False
End If
End Function
Public Function GetHashCode1(ByVal obj As Object) _
As Integer Implements IEqualityComparer.GetHashCode
Return obj.ToString().ToLower().GetHashCode()
End Function
End Class
Public Class SamplesHashtable
Public Shared Sub Main()
' Create a hash table using the default comparer.
Dim myHT1 As New Hashtable()
myHT1.Add("FIRST", "Hello")
myHT1.Add("SECOND", "World")
myHT1.Add("THIRD", "!")
' Create a hash table using the specified IEqualityComparer that uses
' the default Object.Equals to determine equality.
Dim myHT2 As New Hashtable(New myComparer())
myHT2.Add("FIRST", "Hello")
myHT2.Add("SECOND", "World")
myHT2.Add("THIRD", "!")
' Create a hash table using a case-insensitive hash code provider and
' case-insensitive comparer based on the InvariantCulture.
Dim myHT3 As New Hashtable( _
CaseInsensitiveHashCodeProvider.DefaultInvariant, _
CaseInsensitiveComparer.DefaultInvariant)
myHT3.Add("FIRST", "Hello")
myHT3.Add("SECOND", "World")
myHT3.Add("THIRD", "!")
' Create a hash table using an IEqualityComparer that is based on
' the Turkish culture (tr-TR) where "I" is not the uppercase
' version of "i".
Dim myCul As New CultureInfo("tr-TR")
Dim myHT4 As New Hashtable(New myCultureComparer(myCul))
myHT4.Add("FIRST", "Hello")
myHT4.Add("SECOND", "World")
myHT4.Add("THIRD", "!")
' Search for a key in each hash table.
Console.WriteLine("first is in myHT1: {0}", myHT1.ContainsKey("first"))
Console.WriteLine("first is in myHT2: {0}", myHT2.ContainsKey("first"))
Console.WriteLine("first is in myHT3: {0}", myHT3.ContainsKey("first"))
Console.WriteLine("first is in myHT4: {0}", myHT4.ContainsKey("first"))
End Sub
End Class
'This code produces the following output.
'Results vary depending on the system's culture settings.
'first is in myHT1: False
'first is in myHT2: False
'first is in myHT3: True
'first is in myHT4: False
using System;
using System.Collections;
using System.Globalization;
class myComparer : IEqualityComparer
{
public new bool Equals(object x, object y)
{
return x.Equals(y);
}
public int GetHashCode(object obj)
{
return obj.ToString().ToLower().GetHashCode();
}
}
class myCultureComparer : IEqualityComparer
{
public CaseInsensitiveComparer myComparer;
public myCultureComparer()
{
myComparer = CaseInsensitiveComparer.DefaultInvariant;
}
public myCultureComparer(CultureInfo myCulture)
{
myComparer = new CaseInsensitiveComparer(myCulture);
}
public new bool Equals(object x, object y)
{
if (myComparer.Compare(x, y) == 0)
{
return true;
}
else
{
return false;
}
}
public int GetHashCode(object obj)
{
return obj.ToString().ToLower().GetHashCode();
}
}
public class SamplesHashtable
{
public static void Main()
{
// Create a hash table using the default comparer.
Hashtable myHT1 = new Hashtable();
myHT1.Add("FIRST", "Hello");
myHT1.Add("SECOND", "World");
myHT1.Add("THIRD", "!");
// Create a hash table using the specified IEqualityComparer that uses
// the default Object.Equals to determine equality.
Hashtable myHT2 = new Hashtable(new myComparer());
myHT2.Add("FIRST", "Hello");
myHT2.Add("SECOND", "World");
myHT2.Add("THIRD", "!");
// Create a hash table using a case-insensitive hash code provider and
// case-insensitive comparer based on the InvariantCulture.
Hashtable myHT3 = new Hashtable(
CaseInsensitiveHashCodeProvider.DefaultInvariant,
CaseInsensitiveComparer.DefaultInvariant);
myHT3.Add("FIRST", "Hello");
myHT3.Add("SECOND", "World");
myHT3.Add("THIRD", "!");
// Create a hash table using an IEqualityComparer that is based on
// the Turkish culture (tr-TR) where "I" is not the uppercase
// version of "i".
CultureInfo myCul = new CultureInfo("tr-TR");
Hashtable myHT4 = new Hashtable(new myCultureComparer(myCul));
myHT4.Add("FIRST", "Hello");
myHT4.Add("SECOND", "World");
myHT4.Add("THIRD", "!");
// Search for a key in each hash table.
Console.WriteLine("first is in myHT1: {0}", myHT1.ContainsKey("first"));
Console.WriteLine("first is in myHT2: {0}", myHT2.ContainsKey("first"));
Console.WriteLine("first is in myHT3: {0}", myHT3.ContainsKey("first"));
Console.WriteLine("first is in myHT4: {0}", myHT4.ContainsKey("first"));
}
}
/*
This code produces the following output.
Results vary depending on the system's culture settings.
first is in myHT1: False
first is in myHT2: False
first is in myHT3: True
first is in myHT4: False
*/
using namespace System;
using namespace System::Collections;
using namespace System::Globalization;
ref class myComparer : IEqualityComparer
{
public:
virtual bool Equals(Object^ x, Object^ y)
{
return x->Equals(y);
}
virtual int GetHashCode(Object^ obj)
{
return obj->ToString()->ToLower()->GetHashCode();
}
};
ref class myCultureComparer : IEqualityComparer
{
private:
CaseInsensitiveComparer^ myComparer;
public:
myCultureComparer()
{
myComparer = CaseInsensitiveComparer::DefaultInvariant;
}
myCultureComparer(CultureInfo^ myCulture)
{
myComparer = gcnew CaseInsensitiveComparer(myCulture);
}
virtual bool Equals(Object^ x, Object^ y)
{
if (myComparer->Compare(x, y) == 0)
{
return true;
}
else
{
return false;
}
}
virtual int GetHashCode(Object^ obj)
{
return obj->ToString()->ToLower()->GetHashCode();
}
};
int main()
{
// Create a hash table using the default hash code provider and the default comparer.
Hashtable^ myHT1 = gcnew Hashtable((IEqualityComparer^)nullptr);
myHT1->Add( "FIRST", "Hello" );
myHT1->Add( "SECOND", "World" );
myHT1->Add( "THIRD", "!" );
// Create a hash table using the specified IEqualityComparer that uses
// the default Object.Equals to determine equality.
Hashtable^ myHT2 = gcnew Hashtable(gcnew myComparer());
myHT2->Add( "FIRST", "Hello" );
myHT2->Add( "SECOND", "World" );
myHT2->Add( "THIRD", "!" );
// Create a hash table using a case-insensitive hash code provider and
// case-insensitive comparer based on the InvariantCulture.
Hashtable^ myHT3 = gcnew Hashtable(
CaseInsensitiveHashCodeProvider::DefaultInvariant,
CaseInsensitiveComparer::DefaultInvariant);
myHT3->Add( "FIRST", "Hello" );
myHT3->Add( "SECOND", "World" );
myHT3->Add( "THIRD", "!" );
// Create a hash table using an IEqualityComparer that is based on
// the Turkish culture (tr-TR) where "I" is not the uppercase
// version of "i".
CultureInfo^ myCul = gcnew CultureInfo("tr-TR");
Hashtable^ myHT4 = gcnew Hashtable( gcnew myCultureComparer(myCul) );
myHT4->Add( "FIRST", "Hello" );
myHT4->Add( "SECOND", "World" );
myHT4->Add( "THIRD", "!" );
// Search for a key in each hash table.
Console::WriteLine( "first is in myHT1: {0}", myHT1->ContainsKey( "first" ) );
Console::WriteLine( "first is in myHT2: {0}", myHT2->ContainsKey( "first" ) );
Console::WriteLine( "first is in myHT3: {0}", myHT3->ContainsKey( "first" ) );
Console::WriteLine( "first is in myHT4: {0}", myHT4->ContainsKey( "first" ) );
}
/*
This code produces the following output. Results vary depending on the system's culture settings.
first is in myHT1: False
first is in myHT2: False
first is in myHT3: True
first is in myHT4: False
*/
Plattformen
Windows 98, Windows 2000 SP4, Windows Millennium Edition, 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: 1.0, 1.1
Veraltet (Compilerwarnung) in 2.0
.NET Compact Framework
Unterstützt in: 1.0
Veraltet (Compilerwarnung) in 2.0
Siehe auch
Referenz
Hashtable-Klasse
Hashtable-Member
System.Collections-Namespace
IHashCodeProvider
IComparer
Object.GetHashCode
Object.Equals