Hashtable.ContainsKey(Object) Methode
Definition
Wichtig
Einige Informationen beziehen sich auf Vorabversionen, die vor dem Release ggf. grundlegend überarbeitet werden. Microsoft übernimmt hinsichtlich der hier bereitgestellten Informationen keine Gewährleistungen, seien sie ausdrücklich oder konkludent.
Stellt fest, ob der Hashtable einen bestimmten Schlüssel enthält.
public:
virtual bool ContainsKey(System::Object ^ key);
public virtual bool ContainsKey (object key);
abstract member ContainsKey : obj -> bool
override this.ContainsKey : obj -> bool
Public Overridable Function ContainsKey (key As Object) As Boolean
Parameter
Gibt zurück
true
, wenn das Hashtable ein Element mit dem angegebenen Schlüssel enthält, andernfalls false
.
Ausnahmen
key
ist null
.
Beispiele
Im folgenden Beispiel wird gezeigt, wie Ermittelt wird, ob das Hashtable ein bestimmtes Element enthält.
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.
*/
using System;
using System.Collections;
public class SamplesHashtable
{
public static void Main()
{
// Creates and initializes a new Hashtable.
var 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.
var 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($"\t[{i++}]:\t{de.Key}\t{de.Value}");
Console.WriteLine();
}
}
/*
This code produces the following output.
The Hashtable contains the following values:
-INDEX- -KEY- -VALUE-
[0]: 4 four
[1]: 3 three
[2]: 2 two
[3]: 1 one
[4]: 0 zero
The key "2" is in the Hashtable.
The key "6" is NOT in the Hashtable.
The value "three" is in the Hashtable.
The value "nine" is NOT in the Hashtable.
*/
Imports System.Collections
Public Class SamplesHashtable
Public Shared Sub Main()
' Creates and initializes a new Hashtable.
Dim myHT As New Hashtable()
myHT.Add(0, "zero")
myHT.Add(1, "one")
myHT.Add(2, "two")
myHT.Add(3, "three")
myHT.Add(4, "four")
' Displays the values of the Hashtable.
Console.WriteLine("The Hashtable contains the following values:")
PrintIndexAndKeysAndValues(myHT)
' Searches for a specific key.
Dim myKey As Integer = 2
Console.Write($"The key ""{myKey}"" is ")
If (myHT.ContainsKey(myKey))
Console.WriteLine("in the Hashtable.")
Else
Console.WriteLine("NOT in the Hashtable.")
End If
myKey = 6
Console.Write($"The key ""{myKey}"" is ")
If (myHT.ContainsKey(myKey))
Console.WriteLine(" in the Hashtable.")
Else
Console.WriteLine(" NOT in the Hashtable.")
End If
' Searches for a specific value.
Dim myValue As String = "three"
Console.Write("The value ""{0}"" is ", myValue)
If (myHT.ContainsValue(myValue))
Console.WriteLine(" in the Hashtable.")
Else
Console.WriteLine(" NOT in the Hashtable.")
End If
myValue = "nine"
Console.Write($"The value ""{myValue}"" is ")
If (myHT.ContainsValue(myValue))
Console.WriteLine(" in the Hashtable.")
Else
Console.WriteLine(" NOT in the Hashtable.")
End If
End Sub
Public Shared Sub PrintIndexAndKeysAndValues(myHT As Hashtable)
Dim i As Integer = 0
Console.WriteLine(vbTab + "-INDEX-" + vbTab + "-KEY-" + vbTab + "-VALUE-")
For Each de As DictionaryEntry In myHT
Console.WriteLine(vbTab + "[{0}]:" + vbTab + "{1}" + vbTab + "{2}", i, de.Key, de.Value)
i += 1
Next
Console.WriteLine()
End Sub
End Class
' 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.
Hinweise
Diese Methode verhält sich genau wie Contains.
Diese Methode ist ein O(1)
Vorgang.
Ab dem .NET Framework 2.0 verwendet diese Methode die -Objekte Equals und CompareTo -Methoden item
der Auflistung, um zu bestimmen, ob ein Element vorhanden ist. In den früheren Versionen des .NET Framework wurde diese Bestimmung mithilfe der Equals Methoden und CompareTo des item
Parameters für die Objekte in der Auflistung vorgenommen.