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DictionaryBase.GetEnumerator (Método)

Actualización: noviembre 2007

Devuelve una interfaz IDictionaryEnumerator que recorre en iteración la instancia de DictionaryBase.

Espacio de nombres:  System.Collections
Ensamblado:  mscorlib (en mscorlib.dll)

public IDictionaryEnumerator GetEnumerator()
public final IDictionaryEnumerator GetEnumerator()
public final function GetEnumerator() : IDictionaryEnumerator

Valor devuelto

Tipo: System.Collections.IDictionaryEnumerator
Interfaz IDictionaryEnumerator correspondiente a la instancia de DictionaryBase.

Implementaciones

IDictionary.GetEnumerator()

La instrucción foreach del lenguaje C# (for each en Visual Basic) oculta la complejidad de los enumeradores. Por tanto, se recomienda el uso de foreach en lugar de manipular directamente el enumerador.

Los enumeradores pueden utilizarse para leer los datos de la colección, pero no pueden utilizarse para modificar la colección subyacente.

Inicialmente, el enumerador se coloca delante del primer elemento de la colección. Reset también devuelve el enumerador a esta posición. En esta posición, el valor de la propiedad Current está sin definir. Por lo tanto, debe llamar a MoveNext para adelantar el enumerador al primer elemento de la colección antes de leer el valor de Current.

Current devuelve el mismo objeto hasta que se llama a MoveNext o a Reset. MoveNext establece el valor de Current en el siguiente elemento.

Si MoveNext pasa el final de la colección, el enumerador se coloca detrás del último elemento de la colección y MoveNext devuelve false. Cuando el enumerador está en esta posición, las llamadas posteriores al método MoveNext también devuelven false. Si la última llamada al método MoveNext devuelve false, el valor de la propiedad Current queda sin definir. Para volver a establecer el valor de Current en el primer elemento de la colección, se puede llamar primero al método Reset y después al método MoveNext.

Mientras no se modifique la colección, el enumerador continúa siendo válido. Si se realizan cambios en la colección, como agregar, modificar o eliminar elementos, el enumerador se invalida definitivamente y tiene un comportamiento no definido.

El enumerador no tiene acceso exclusivo a la colección; por lo tanto, la enumeración a través de una colección es un procedimiento que, en esencia, no es seguro para la ejecución de subprocesos. Para garantizar la seguridad en la ejecución de subprocesos durante la enumeración, puede bloquear la colección durante toda la enumeración. Para permitir que varios subprocesos obtengan acceso de lectura y escritura a la colección, debe implementar su propia sincronización.

Este método es una operación O(1).

El siguiente ejemplo de código implementa la clase DictionaryBase y utiliza dicha implementación para crear un diccionario de claves y valores String que tienen una propiedad Length de 5 caracteres o menos.

using System;
using System.Collections;

public class ShortStringDictionary : DictionaryBase  {

   public String this[ String key ]  {
      get  {
         return( (String) Dictionary[key] );
      }
      set  {
         Dictionary[key] = value;
      }
   }

   public ICollection Keys  {
      get  {
         return( Dictionary.Keys );
      }
   }

   public ICollection Values  {
      get  {
         return( Dictionary.Values );
      }
   }

   public void Add( String key, String value )  {
      Dictionary.Add( key, value );
   }

   public bool Contains( String key )  {
      return( Dictionary.Contains( key ) );
   }

   public void Remove( String key )  {
      Dictionary.Remove( key );
   }

   protected override void OnInsert( Object key, Object value )  {
      if ( key.GetType() != typeof(System.String) )
         throw new ArgumentException( "key must be of type String.", "key" );
      else  {
         String strKey = (String) key;
         if ( strKey.Length > 5 )
            throw new ArgumentException( "key must be no more than 5 characters in length.", "key" );
      }

      if ( value.GetType() != typeof(System.String) )
         throw new ArgumentException( "value must be of type String.", "value" );
      else  {
         String strValue = (String) value;
         if ( strValue.Length > 5 )
            throw new ArgumentException( "value must be no more than 5 characters in length.", "value" );
      }
   }

   protected override void OnRemove( Object key, Object value )  {
      if ( key.GetType() != typeof(System.String) )
         throw new ArgumentException( "key must be of type String.", "key" );
      else  {
         String strKey = (String) key;
         if ( strKey.Length > 5 )
            throw new ArgumentException( "key must be no more than 5 characters in length.", "key" );
      }
   }

   protected override void OnSet( Object key, Object oldValue, Object newValue )  {
      if ( key.GetType() != typeof(System.String) )
         throw new ArgumentException( "key must be of type String.", "key" );
      else  {
         String strKey = (String) key;
         if ( strKey.Length > 5 )
            throw new ArgumentException( "key must be no more than 5 characters in length.", "key" );
      }

      if ( newValue.GetType() != typeof(System.String) )
         throw new ArgumentException( "newValue must be of type String.", "newValue" );
      else  {
         String strValue = (String) newValue;
         if ( strValue.Length > 5 )
            throw new ArgumentException( "newValue must be no more than 5 characters in length.", "newValue" );
      }
   }

   protected override void OnValidate( Object key, Object value )  {
      if ( key.GetType() != typeof(System.String) )
         throw new ArgumentException( "key must be of type String.", "key" );
      else  {
         String strKey = (String) key;
         if ( strKey.Length > 5 )
            throw new ArgumentException( "key must be no more than 5 characters in length.", "key" );
      }

      if ( value.GetType() != typeof(System.String) )
         throw new ArgumentException( "value must be of type String.", "value" );
      else  {
         String strValue = (String) value;
         if ( strValue.Length > 5 )
            throw new ArgumentException( "value must be no more than 5 characters in length.", "value" );
      }
   }

}


public class SamplesDictionaryBase  {

   public static void Main()  {

      // Creates and initializes a new DictionaryBase.
      ShortStringDictionary mySSC = new ShortStringDictionary();

      // Adds elements to the collection.
      mySSC.Add( "One", "a" );
      mySSC.Add( "Two", "ab" );
      mySSC.Add( "Three", "abc" );
      mySSC.Add( "Four", "abcd" );
      mySSC.Add( "Five", "abcde" );

      // Display the contents of the collection using foreach. This is the preferred method.
      Console.WriteLine( "Contents of the collection (using foreach):" );
      PrintKeysAndValues1( mySSC );

      // Display the contents of the collection using the enumerator.
      Console.WriteLine( "Contents of the collection (using enumerator):" );
      PrintKeysAndValues2( mySSC );

      // Display the contents of the collection using the Keys property and the Item property.
      Console.WriteLine( "Initial contents of the collection (using Keys and Item):" );
      PrintKeysAndValues3( mySSC );

      // Tries to add a value that is too long.
      try  {
         mySSC.Add( "Ten", "abcdefghij" );
      }
      catch ( ArgumentException e )  {
         Console.WriteLine( e.ToString() );
      }

      // Tries to add a key that is too long.
      try  {
         mySSC.Add( "Eleven", "ijk" );
      }
      catch ( ArgumentException e )  {
         Console.WriteLine( e.ToString() );
      }

      Console.WriteLine();

      // Searches the collection with Contains.
      Console.WriteLine( "Contains \"Three\": {0}", mySSC.Contains( "Three" ) );
      Console.WriteLine( "Contains \"Twelve\": {0}", mySSC.Contains( "Twelve" ) );
      Console.WriteLine();

      // Removes an element from the collection.
      mySSC.Remove( "Two" );

      // Displays the contents of the collection.
      Console.WriteLine( "After removing \"Two\":" );
      PrintKeysAndValues1( mySSC );

   }

   // Uses the foreach statement which hides the complexity of the enumerator.
   // NOTE: The foreach statement is the preferred way of enumerating the contents of a collection.
   public static void PrintKeysAndValues1( ShortStringDictionary myCol )  {
      foreach ( DictionaryEntry myDE in myCol )
         Console.WriteLine( "   {0,-5} : {1}", myDE.Key, myDE.Value );
      Console.WriteLine();
   }

   // Uses the enumerator. 
   // NOTE: The foreach statement is the preferred way of enumerating the contents of a collection.
   public static void PrintKeysAndValues2( ShortStringDictionary myCol )  {
      DictionaryEntry myDE;
      System.Collections.IEnumerator myEnumerator = myCol.GetEnumerator();
      while ( myEnumerator.MoveNext() )
         if ( myEnumerator.Current != null )  {
            myDE = (DictionaryEntry) myEnumerator.Current;
            Console.WriteLine( "   {0,-5} : {1}", myDE.Key, myDE.Value );
         }
      Console.WriteLine();
   }

   // Uses the Keys property and the Item property.
   public static void PrintKeysAndValues3( ShortStringDictionary myCol )  {
      ICollection myKeys = myCol.Keys;
      foreach ( String k in myKeys )
         Console.WriteLine( "   {0,-5} : {1}", k, myCol[k] );
      Console.WriteLine();
   }

}


/* 
This code produces the following output.

Contents of the collection (using foreach):
   Three : abc
   Five  : abcde
   Two   : ab
   One   : a
   Four  : abcd

Contents of the collection (using enumerator):
   Three : abc
   Five  : abcde
   Two   : ab
   One   : a
   Four  : abcd

Initial contents of the collection (using Keys and Item):
   Three : abc
   Five  : abcde
   Two   : ab
   One   : a
   Four  : abcd

System.ArgumentException: value must be no more than 5 characters in length.
Parameter name: value
   at ShortStringDictionary.OnValidate(Object key, Object value)
   at System.Collections.DictionaryBase.System.Collections.IDictionary.Add(Object key, Object value)
   at SamplesDictionaryBase.Main()
System.ArgumentException: key must be no more than 5 characters in length.
Parameter name: key
   at ShortStringDictionary.OnValidate(Object key, Object value)
   at System.Collections.DictionaryBase.System.Collections.IDictionary.Add(Object key, Object value)
   at SamplesDictionaryBase.Main()

Contains "Three": True
Contains "Twelve": False

After removing "Two":
   Three : abc
   Five  : abcde
   One   : a
   Four  : abcd

*/



import System.*;
import System.Collections.*;

public class ShortStringDictionary extends DictionaryBase
{
    /** @property 
     */
    public String get_Value(String key)
    {
        return((String)(get_Dictionary().get_Item(key)));
    } //get_Value

    /** @property 
     */
    public void set_Value(String key,String value)
    {
        get_Dictionary().set_Item(key, value);
    } //set_Value


    /** @property 
     */
    public ICollection get_Keys()
    {
        return get_Dictionary().get_Keys();
    } //get_Keys

    /** @property 
     */
    public ICollection get_Values()
    {
        return get_Dictionary().get_Values();
    } //get_Values

    public void Add(String key, String value) 
    {
        get_Dictionary().Add(key, value);
    } //Add

    public boolean Contains(String key) 
    {
        return get_Dictionary().Contains(key);
    } //Contains

    public void Remove(String key) 
    {
        get_Dictionary().Remove(key);
    } //Remove

    protected void OnInsert(Object key, Object value) 
    {
        if (!key.GetType().Equals(Type.GetType("System.String"))) {
            throw new ArgumentException("key must be of type String.", "key");
        }
        else {
            String strKey = ((String)(key));
            if (strKey.length() > 5) {
                throw new ArgumentException("key must be no more than "
                    + "5 characters in length.", "key");
            }
        }  
        if (!value.GetType().Equals(Type.GetType("System.String"))) {
            throw new ArgumentException("value must be of type String.", 
                "value");
        }
        else {
            String strValue = (String)value;
            if (strValue.length() > 5) {
                throw new ArgumentException("value must be no more than "
                    + "5 characters in length.", "value");
            }
        }
    } //OnInsert

    protected void OnRemove(Object key, Object value) 
    {
        if (!key.GetType().Equals(Type.GetType("System.String"))) {
            throw new ArgumentException("key must be of type String.", "key");
        }
        else {
            String strKey = ((String)(key));
            if (strKey.length() > 5) {
                throw new ArgumentException("key must be no more than "
                    + "5 characters in length.", "key");
            }
        }
    } //OnRemove

    protected void OnSet(Object key, Object oldValue, Object newValue) 
    {
        if (!key.GetType().Equals(Type.GetType("System.String"))) {
            throw new ArgumentException("key must be of type String.", "key");
        }
        else {
            String strKey = (String)key;
            if (strKey.length() > 5) {
                throw new ArgumentException("key must be no more than "
                    + "5 characters in length.", "key") ;
            }
        }
        if (!newValue.GetType().Equals(Type.GetType("System.String"))) {
            throw new ArgumentException("newValue must be of type String.",
                "newValue") ;
        }
        else {
            String strValue = ((String)(newValue));
            if (strValue.length() > 5) {
                throw new ArgumentException("newValue must be no more than "
                    + "5 characters in length.", "newValue") ;
            }
        }
    } //OnSet

    protected void OnValidate(Object key, Object value) 
    {
        if (!key.GetType().Equals(Type.GetType("System.String"))) {
            throw new ArgumentException("key must be of type String.", "key");
        }
        else {
            String strKey = ((String)(key));
            if (strKey.length() > 5) {
                throw new ArgumentException("key must be no more than "
                    + "5 characters in length.", "key") ;
            }
        }   
        if (!value.GetType().Equals(Type.GetType("System.String"))) {
            throw new ArgumentException("value must be of type String.", 
                "value");
        }
        else {
            String strValue = ((String)(value));
            if (strValue.length() > 5) {
                throw new ArgumentException("value must be no more than "
                    + "5 characters in length.", "value") ;
            }
        }
    } //OnValidate
} //ShortStringDictionary

public class SamplesDictionaryBase
{
    public static void main(String[] args)
    {
        // Creates and initializes a new DictionaryBase.
        ShortStringDictionary mySSC =  new ShortStringDictionary();

        // Adds elements to the collection.
        mySSC.Add("One", "a");
        mySSC.Add("Two", "ab");
        mySSC.Add("Three", "abc");
        mySSC.Add("Four", "abcd");
        mySSC.Add("Five", "abcde");

        // Display the contents of the collection using while. This is the
        // preferred method.
        Console.WriteLine("Contents of the collection (using for):");
        PrintKeysAndValues1(mySSC);

        // Display the contents of the collection using the enumerator.
        Console.WriteLine("Contents of the collection (using enumerator):");
        PrintKeysAndValues2(mySSC);

        // Display the contents of the collection using the Keys property and
        // the Item property.
        Console.WriteLine("Initial contents of the collection (using Keys"
            + " and Item):");
        PrintKeysAndValues3(mySSC);

        // Tries to add a value that is too long.
        try {
            mySSC.Add("Ten", "abcdefghij");
        }
        catch(ArgumentException e) {
            Console.WriteLine(e.ToString());
        }

        // Tries to add a key that is too long.
        try {
            mySSC.Add("Eleven", "ijk");
        }
        catch(ArgumentException e) {
            Console.WriteLine(e.ToString());
        }
        Console.WriteLine();

        // Searches the collection with Contains.
        boolean b = mySSC.Contains("Three");
        Console.Write("Contains \"Three\": ");
        Console.WriteLine(b);
        b = mySSC.Contains("Twelve");
        Console.Write("Contains \"Twelve\": ");
        Console.WriteLine(b);
        Console.WriteLine();

        // Removes an element from the collection.
        mySSC.Remove("Two");

        // Displays the contents of the collection.
        Console.WriteLine("After removing \"Two\":");
        PrintKeysAndValues1(mySSC);
    }//main

    // Uses the for statement which hides the complexity of the enumerator.
    // NOTE: The for statement is the preferred way of enumerating the 
    // contents of a collection.
    public static void PrintKeysAndValues1(ShortStringDictionary myCol) 
    {
        String strValue;
        String strKeys[] = new String[myCol.get_Count()];
        myCol.get_Keys().CopyTo(strKeys,0);

        for (int iCtr = 0; iCtr < myCol.get_Count(); iCtr++){
            strValue = myCol.get_Value(strKeys[iCtr]);
            Console.WriteLine("   {0,-5} : {1}", strKeys[iCtr], strValue);
        }
        Console.WriteLine();
    } //PrintKeysAndValues1

    // Uses the enumerator. 
    // NOTE: The for statement is the preferred way of enumerating the 
    // contents of a collection.
    public static void PrintKeysAndValues2(ShortStringDictionary myCol) 
    {
        DictionaryEntry myDE;
        System.Collections.IEnumerator myEnumerator = myCol.GetEnumerator();
        while(myEnumerator.MoveNext()) {
            if ( myEnumerator.get_Current()  != null  ) {
                myDE =((DictionaryEntry)(myEnumerator.get_Current()));
                Console.WriteLine("   {0,-5} : {1}", myDE.get_Key(), 
                myDE.get_Value());
            }
        }
        Console.WriteLine();
    } //PrintKeysAndValues2

    // Uses the Keys property and the Value property.
    public static void PrintKeysAndValues3(ShortStringDictionary myCol) 
    {
        ICollection myKeys = myCol.get_Keys();
        IEnumerator myEnumerator = myKeys.GetEnumerator();
        while (myEnumerator.MoveNext()) {
            String k = myEnumerator.get_Current().ToString();
            Console.WriteLine("   {0,-5} : {1}", k, myCol.get_Item(k));
        }
        Console.WriteLine();
    } //PrintKeysAndValues3
} //SamplesDictionaryBase

/* 
This code produces the following output.

Contents of the collection (using while):
   Three : abc
   Five  : abcde
   Two   : ab
   One   : a
   Four  : abcd

Contents of the collection (using enumerator):
   Three : abc
   Five  : abcde
   Two   : ab
   One   : a
   Four  : abcd

Initial contents of the collection (using Keys and Item):
   Three : abc
   Five  : abcde
   Two   : ab
   One   : a
   Four  : abcd

System.ArgumentException: value must be no more than 5 characters in length.
Parameter name: value
   at ShortStringDictionary.OnValidate(Object key, Object value)
   at System.Collections.DictionaryBase.System.Collections.IDictionary.Add(
Object key, Object value)
   at SamplesDictionaryBase.Main()
System.ArgumentException: key must be no more than 5 characters in length.
Parameter name: key
   at ShortStringDictionary.OnValidate(Object key, Object value)
   at System.Collections.DictionaryBase.System.Collections.IDictionary.Add(
Object key, Object value)
   at SamplesDictionaryBase.Main()

Contains "Three": True
Contains "Twelve": False

After removing "Two":
   Three : abc
   Five  : abcde
   One   : a
   Four  : abcd

*/



Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

.NET Framework y .NET Compact Framework no admiten todas las versiones de cada plataforma. Para obtener una lista de las versiones compatibles, vea Requisitos de sistema de .NET Framework.

.NET Framework

Compatible con: 3.5, 3.0, 2.0, 1.1, 1.0

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