StringDictionary.ContainsKey(String) Methode

Definitie

Naamruimte:
System.Collections.Specialized
Assembly's:
System.dll, System.Collections.Specialized.dll
Assembly:
System.dll
Assembly:
netstandard.dll

Bepaalt of de StringDictionary sleutel een specifieke sleutel bevat.

public:
 virtual bool ContainsKey(System::String ^ key);
public virtual bool ContainsKey(string key);
abstract member ContainsKey : string -> bool
override this.ContainsKey : string -> bool
Public Overridable Function ContainsKey (key As String) As Boolean

Parameters

key
String

De sleutel die moet worden gevonden in de StringDictionary.

Retouren

Boolean

trueals de StringDictionary vermelding een vermelding met de opgegeven sleutel bevat; anders. false

Uitzonderingen

ArgumentNullException

De sleutel is null.

Voorbeelden

In het volgende codevoorbeeld wordt gezocht naar een element in een StringDictionary.

using System;
using System.Collections;
using System.Collections.Specialized;

public class SamplesStringDictionary  {

   public static void Main()  {

      // Creates and initializes a new StringDictionary.
      StringDictionary myCol = new StringDictionary();
      myCol.Add( "red", "rojo" );
      myCol.Add( "green", "verde" );
      myCol.Add( "blue", "azul" );

      // Displays the values in the StringDictionary.
      Console.WriteLine( "Initial contents of the StringDictionary:" );
      PrintKeysAndValues( myCol );

      // Searches for a key.
      if ( myCol.ContainsKey( "red" ) )
         Console.WriteLine( "The collection contains the key \"red\"." );
      else
         Console.WriteLine( "The collection does not contain the key \"red\"." );
      Console.WriteLine();

      // Searches for a value.
      if ( myCol.ContainsValue( "amarillo" ) )
         Console.WriteLine( "The collection contains the value \"amarillo\"." );
      else
         Console.WriteLine( "The collection does not contain the value \"amarillo\"." );
      Console.WriteLine();
   }

   public static void PrintKeysAndValues( StringDictionary myCol )  {
      Console.WriteLine( "   KEY        VALUE" );
      foreach ( DictionaryEntry de in myCol )
         Console.WriteLine( "   {0,-10} {1}", de.Key, de.Value );
      Console.WriteLine();
   }
}

/*
This code produces the following output.

Initial contents of the StringDictionary:
   KEY        VALUE
   green      verde
   red        rojo
   blue       azul

The collection contains the key "red".

The collection does not contain the value "amarillo".

*/

Imports System.Collections
Imports System.Collections.Specialized

Public Class SamplesStringDictionary   

   Public Shared Sub Main()

      ' Creates and initializes a new StringDictionary.
      Dim myCol As New StringDictionary()
      myCol.Add("red", "rojo")
      myCol.Add("green", "verde")
      myCol.Add("blue", "azul")

      ' Displays the values in the StringDictionary.
      Console.WriteLine("Initial contents of the StringDictionary:")
      PrintKeysAndValues(myCol)

      ' Searches for a key.
      If myCol.ContainsKey("red") Then
         Console.WriteLine("The collection contains the key ""red"".")
      Else
         Console.WriteLine("The collection does not contain the key ""red"".")
      End If
      Console.WriteLine()

      ' Searches for a value.
      If myCol.ContainsValue("amarillo") Then
         Console.WriteLine("The collection contains the value ""amarillo"".")
      Else
         Console.WriteLine("The collection does not contain the value ""amarillo"".")
      End If
      Console.WriteLine()

   End Sub

   Public Shared Sub PrintKeysAndValues(myCol As StringDictionary)
      Dim de As DictionaryEntry

      Console.WriteLine("   KEY        VALUE")
      For Each de In  myCol
         Console.WriteLine("   {0,-10} {1}", de.Key, de.Value)
      Next de
      Console.WriteLine()

   End Sub

End Class


'This code produces the following output.
'
'Initial contents of the StringDictionary:
'   KEY        VALUE
'   green      verde
'   red        rojo
'   blue       azul
'
'The collection contains the key "red".
'
'The collection does not contain the value "amarillo".

Opmerkingen

De sleutel wordt op een niet-hoofdlettergevoelige manier verwerkt; wordt omgezet in kleine letters voordat deze wordt gebruikt.

Deze methode is een O(1)-bewerking.

Deze methode maakt gebruik van de objecten Equals en CompareTo methoden item van de verzameling om te bepalen of item deze bestaat.

Van toepassing op

Zie ook