Hashtable.ContainsKey-Methode
Bestimmt, ob die Hashtable einen bestimmten Schlüssel enthält.
Namespace: System.Collections
Assembly: mscorlib (in mscorlib.dll)
Syntax
'Declaration
Public Overridable Function ContainsKey ( _
key As Object _
) As Boolean
'Usage
Dim instance As Hashtable
Dim key As Object
Dim returnValue As Boolean
returnValue = instance.ContainsKey(key)
public virtual bool ContainsKey (
Object key
)
public:
virtual bool ContainsKey (
Object^ key
)
public boolean ContainsKey (
Object key
)
public function ContainsKey (
key : Object
) : boolean
Parameter
- key
Der in der Hashtable zu suchende Schlüssel.
Rückgabewert
true, wenn die Hashtable ein Element mit dem angegebenen Schlüssel enthält, andernfalls false.
Ausnahmen
Ausnahmetyp | Bedingung |
---|---|
key ist NULL (Nothing in Visual Basic). |
Hinweise
Diese Methode verhält sich genauso wie Contains.
Diese Methode ist eine O(1)-Operation.
Beispiel
Im folgenden Beispiel wird gezeigt, wie das Vorhandensein eines bestimmten Elements in der Hashtable geprüft wird.
Imports System
Imports System.Collections
Public Class SamplesHashtable
Public Shared Sub Main()
' Creates and initializes a new Hashtable.
Dim myHT As New Hashtable()
myHT.Add(0, "zero")
myHT.Add(1, "one")
myHT.Add(2, "two")
myHT.Add(3, "three")
myHT.Add(4, "four")
' Displays the values of the Hashtable.
Console.WriteLine("The Hashtable contains the following values:")
PrintIndexAndKeysAndValues(myHT)
' Searches for a specific key.
Dim myKey As Integer = 2
Console.Write("The key ""{0}"" is ", myKey)
If(myHT.ContainsKey(myKey))
Console.WriteLine("in the Hashtable.")
Else
Console.WriteLine("NOT in the Hashtable.")
End If
myKey = 6
Console.Write("The key ""{0}"" is ", myKey)
If(myHT.ContainsKey(myKey))
Console.WriteLine(" in the Hashtable.")
Else
Console.WriteLine(" NOT in the Hashtable.")
End If
' Searches for a specific value.
Dim myValue As String = "three"
Console.Write("The value ""{0}"" is ", myValue)
If(myHT.ContainsValue(myValue))
Console.WriteLine(" in the Hashtable.")
Else
Console.WriteLine(" NOT in the Hashtable.")
End If
myValue = "nine"
Console.Write("The value ""{0}"" is ", myValue)
If(myHT.ContainsValue(myValue))
Console.WriteLine(" in the Hashtable.")
Else
Console.WriteLine(" NOT in the Hashtable.")
End If
End Sub 'Main
Public Shared Sub PrintIndexAndKeysAndValues(myHT As Hashtable)
Dim i As Integer = 0
Console.WriteLine(vbTab + "-INDEX-" + vbTab + "-KEY-" + vbTab + "-VALUE-")
Dim de As DictionaryEntry
For Each de In myHT
Console.WriteLine(vbTab + "[{0}]:" + vbTab + "{1}" + vbTab + "{2}", i, de.Key, de.Value)
i = i + 1
Next de
Console.WriteLine()
End Sub 'PrintIndexAndKeysAndValues
End Class 'SamplesHashtable
' This code produces the following output.
'
' The Hashtable contains the following values:
' -INDEX- -KEY- -VALUE-
' [0]: 4 four
' [1]: 3 three
' [2]: 2 two
' [3]: 1 one
' [4]: 0 zero
'
' The key "2" is in the Hashtable.
' The key "6" is NOT in the Hashtable.
' The value "three" is in the Hashtable.
' The value "nine" is NOT in the Hashtable.
using System;
using System.Collections;
public class SamplesHashtable {
public static void Main() {
// Creates and initializes a new Hashtable.
Hashtable myHT = new Hashtable();
myHT.Add( 0, "zero" );
myHT.Add( 1, "one" );
myHT.Add( 2, "two" );
myHT.Add( 3, "three" );
myHT.Add( 4, "four" );
// Displays the values of the Hashtable.
Console.WriteLine( "The Hashtable contains the following values:" );
PrintIndexAndKeysAndValues( myHT );
// Searches for a specific key.
int myKey = 2;
Console.WriteLine( "The key \"{0}\" is {1}.", myKey, myHT.ContainsKey( myKey ) ? "in the Hashtable" : "NOT in the Hashtable" );
myKey = 6;
Console.WriteLine( "The key \"{0}\" is {1}.", myKey, myHT.ContainsKey( myKey ) ? "in the Hashtable" : "NOT in the Hashtable" );
// Searches for a specific value.
String myValue = "three";
Console.WriteLine( "The value \"{0}\" is {1}.", myValue, myHT.ContainsValue( myValue ) ? "in the Hashtable" : "NOT in the Hashtable" );
myValue = "nine";
Console.WriteLine( "The value \"{0}\" is {1}.", myValue, myHT.ContainsValue( myValue ) ? "in the Hashtable" : "NOT in the Hashtable" );
}
public static void PrintIndexAndKeysAndValues( Hashtable myHT ) {
int i = 0;
Console.WriteLine( "\t-INDEX-\t-KEY-\t-VALUE-" );
foreach ( DictionaryEntry de in myHT )
Console.WriteLine( "\t[{0}]:\t{1}\t{2}", i++, de.Key, de.Value );
Console.WriteLine();
}
}
/*
This code produces the following output.
The Hashtable contains the following values:
-INDEX- -KEY- -VALUE-
[0]: 4 four
[1]: 3 three
[2]: 2 two
[3]: 1 one
[4]: 0 zero
The key "2" is in the Hashtable.
The key "6" is NOT in the Hashtable.
The value "three" is in the Hashtable.
The value "nine" is NOT in the Hashtable.
*/
using namespace System;
using namespace System::Collections;
void PrintIndexAndKeysAndValues( Hashtable^ myHT );
int main()
{
// Creates and initializes a new Hashtable.
Hashtable^ myHT = gcnew Hashtable;
myHT->Add( (int^)0, "zero" );
myHT->Add( 1, "one" );
myHT->Add( 2, "two" );
myHT->Add( 3, "three" );
myHT->Add( 4, "four" );
// Displays the values of the Hashtable.
Console::WriteLine( "The Hashtable contains the following values:" );
PrintIndexAndKeysAndValues( myHT );
// Searches for a specific key.
int myKey = 2;
Console::WriteLine( "The key \"{0}\" is {1}.", myKey, myHT->ContainsKey( myKey ) ? (String^)"in the Hashtable" : "NOT in the Hashtable" );
myKey = 6;
Console::WriteLine( "The key \"{0}\" is {1}.", myKey, myHT->ContainsKey( myKey ) ? (String^)"in the Hashtable" : "NOT in the Hashtable" );
// Searches for a specific value.
String^ myValue = "three";
Console::WriteLine( "The value \"{0}\" is {1}.", myValue, myHT->ContainsValue( myValue ) ? (String^)"in the Hashtable" : "NOT in the Hashtable" );
myValue = "nine";
Console::WriteLine( "The value \"{0}\" is {1}.", myValue, myHT->ContainsValue( myValue ) ? (String^)"in the Hashtable" : "NOT in the Hashtable" );
}
void PrintIndexAndKeysAndValues( Hashtable^ myHT )
{
int i = 0;
Console::WriteLine( "\t-INDEX-\t-KEY-\t-VALUE-" );
IEnumerator^ myEnum = myHT->GetEnumerator();
while ( myEnum->MoveNext() )
{
DictionaryEntry de = *safe_cast<DictionaryEntry ^>(myEnum->Current);
Console::WriteLine( "\t[{0}]:\t{1}\t{2}", i++, de.Key, de.Value );
}
Console::WriteLine();
}
/*
This code produces the following output.
The Hashtable contains the following values:
-INDEX- -KEY- -VALUE-
[0]: 4 four
[1]: 3 three
[2]: 2 two
[3]: 1 one
[4]: 0 zero
The key "2" is in the Hashtable.
The key "6" is NOT in the Hashtable.
The value "three" is in the Hashtable.
The value "nine" is NOT in the Hashtable.
*/
import System.*;
import System.Collections.*;
public class SamplesHashtable
{
public static void main(String[] args)
{
// Creates and initializes a new Hashtable.
Hashtable myHT = new Hashtable();
myHT.Add(new Integer(0), "zero");
myHT.Add(new Integer(1), "one");
myHT.Add(new Integer(2), "two");
myHT.Add(new Integer(3), "three");
myHT.Add(new Integer(4), "four");
// Displays the values of the Hashtable.
Console.WriteLine("The Hashtable contains the following values:");
PrintIndexAndKeysAndValues(myHT);
// Searches for a specific key.
int myKey = 2;
Console.WriteLine("The key \"{0}\" is {1}.",
System.Convert.ToString(myKey),
(myHT.ContainsKey(new Integer(myKey))) ?
"in the Hashtable" : "NOT in the Hashtable");
myKey = 6;
Console.WriteLine("The key \"{0}\" is {1}.",
System.Convert.ToString(myKey),
(myHT.ContainsKey(new Integer(myKey))) ?
"in the Hashtable" : "NOT in the Hashtable");
// Searches for a specific value.
String myValue = "three";
Console.WriteLine("The value \"{0}\" is {1}.", myValue,
(myHT.ContainsValue(myValue)) ?
"in the Hashtable" : "NOT in the Hashtable");
myValue = "nine";
Console.WriteLine("The value \"{0}\" is {1}.", myValue,
(myHT.ContainsValue(myValue)) ?
"in the Hashtable" : "NOT in the Hashtable");
} //main
public static void PrintIndexAndKeysAndValues(Hashtable myHT)
{
int i = 0;
Console.WriteLine("\t-INDEX-\t-KEY-\t-VALUE-");
IEnumerator myEnumerator = myHT.GetEnumerator();
while (myEnumerator.MoveNext()) {
DictionaryEntry de = (DictionaryEntry)myEnumerator.get_Current();
Console.WriteLine("\t[{0}]:\t{1}\t{2}",
System.Convert.ToString(i++),
de.get_Key().toString(), de.get_Value().toString());
}
Console.WriteLine();
} //PrintIndexAndKeysAndValues
} //SamplesHashtable
/*
This code produces the following output.
The Hashtable contains the following values:
-INDEX- -KEY- -VALUE-
[0]: 4 four
[1]: 3 three
[2]: 2 two
[3]: 1 one
[4]: 0 zero
The key "2" is in the Hashtable.
The key "6" is NOT in the Hashtable.
The value "three" is in the Hashtable.
The value "nine" is NOT in the Hashtable.
*/
import System
import System.Collections
import Microsoft.VisualBasic
// Creates and initializes a new Hashtable.
var myHT : Hashtable = new Hashtable()
myHT.Add(0, "zero")
myHT.Add(1, "one")
myHT.Add(2, "two")
myHT.Add(3, "three")
myHT.Add(4, "four")
// Displays the values of the Hashtable.
Console.WriteLine("The Hashtable contains the following values:")
PrintIndexAndKeysAndValues(myHT)
// Searches for a specific key.
var msg : String
var myKey : int = 2
if(myHT.ContainsKey(myKey))
msg = "in the Hashtable"
else
msg = "NOT in the Hashtable"
Console.WriteLine("The key \"{0}\" is {1}.", myKey, msg)
myKey = 6
if(myHT.ContainsKey(myKey))
msg = "in the Hashtable"
else
msg = "NOT in the Hashtable"
Console.WriteLine("The key \"{0}\" is {1}.", myKey, msg)
// Searches for a specific value.
var myValue : String = "three"
if(myHT.ContainsValue(myValue))
msg = "in the Hashtable"
else
msg = "NOT in the Hashtable"
Console.WriteLine("The value \"{0}\" is {1}.", myValue, msg)
myValue = "nine"
if(myHT.ContainsValue(myValue))
msg = "in the Hashtable"
else
msg = "NOT in the Hashtable"
Console.WriteLine("The value \"{0}\" is {1}.", myValue, msg)
function PrintIndexAndKeysAndValues(myList : Hashtable){
var myEnumerator : IDictionaryEnumerator = myList.GetEnumerator()
var i : int = 0
Console.WriteLine("\t-INDEX-\t-KEY-\t-VALUE-")
while(myEnumerator.MoveNext()){
Console.WriteLine("\t[{0}]:\t{1}\t{2}", i++, myEnumerator.Key,
myEnumerator.Value)
}
Console.WriteLine()
}
// This code produces the following output.
//
// The Hashtable contains the following values:
// -INDEX- -KEY- -VALUE-
// [0]: 4 four
// [1]: 3 three
// [2]: 2 two
// [3]: 1 one
// [4]: 0 zero
//
// The key "2" is in the Hashtable.
// The key "6" is NOT in the Hashtable.
// The value "three" is in the Hashtable.
// The value "nine" is NOT in the Hashtable.
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
Hashtable-Klasse
Hashtable-Member
System.Collections-Namespace
Contains
ContainsValue