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GetEnumerator Method

StringDictionary.GetEnumerator Method

Returns an enumerator that can iterate through the string dictionary.

[Visual Basic]
Public Overridable Function GetEnumerator() As IEnumerator _
   Implements IEnumerable.GetEnumerator
[C#]
public virtual IEnumerator GetEnumerator();
[C++]
public: virtual IEnumerator* GetEnumerator();
[JScript]
public function GetEnumerator() : IEnumerator;

Return Value

An IEnumerator that can iterate through the string dictionary.

Implements

IEnumerable.GetEnumerator

Remarks

Enumerators only allow reading the data in the collection. Enumerators cannot be used to modify the underlying collection.

Initially, the enumerator is positioned before the first element in the collection. Reset also brings the enumerator back to this position. At this position, calling Current throws an exception. Therefore, you must call MoveNext to advance the enumerator to the first element of the collection before reading the value of Current.

Current returns the same object until either MoveNext or Reset is called. MoveNext sets Current to the next element.

After the end of the collection is passed, the enumerator is positioned after the last element in the collection, and calling MoveNext returns false. If the last call to MoveNext returned false, calling Current throws an exception. To set Current to the first element of the collection again, you can call Reset followed by MoveNext.

An enumerator remains valid as long as the collection remains unchanged. If changes are made to the collection, such as adding, modifying or deleting elements, the enumerator is irrecoverably invalidated and the next call to MoveNext or Reset throws an InvalidOperationException. If the collection is modified between MoveNext and Current, Current will return the element that it is set to, even if the enumerator is already invalidated.

The enumerator does not have exclusive access to the collection; therefore, enumerating through a collection is intrinsically not a thread-safe procedure. Even when a collection is synchronized, other threads could still modify the collection, which causes the enumerator to throw an exception. To guarantee thread safety during enumeration, you can either lock the collection during the entire enumeration or catch the exceptions resulting from changes made by other threads.

Example

[Visual Basic, C#, C++] The following code example enumerates the elements of a StringDictionary.

[Visual Basic] 
Imports System
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 in two different ways.
      Console.WriteLine("Displays the elements using for each:")
      PrintKeysAndValues(myCol)
      Console.WriteLine("Displays the elements using the Keys, Values, Count, and indexer properties:")
      PrintKeysAndValues2(myCol)

   End Sub 'Main

   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 'PrintKeysAndValues

   Public Shared Sub PrintKeysAndValues2(myCol As StringDictionary)
      Dim myKeys(myCol.Count) As [String]
      myCol.Keys.CopyTo(myKeys, 0)

      Console.WriteLine("   [INDEX] KEY        VALUE")
      Dim i As Integer
      For i = 0 To myCol.Count - 1
         Console.WriteLine("   [{0}]     {1,-10} {2}", i, myKeys(i), myCol(myKeys(i)))
      Next i
      Console.WriteLine()

   End Sub 'PrintKeysAndValues2

End Class 'SamplesStringDictionary 


'This code produces the following output.
'
'Displays the elements using for each:
'   KEY        VALUE
'   green      verde
'   red        rojo
'   blue       azul
'
'Displays the elements using the Keys, Values, Count, and indexer properties:
'   [INDEX] KEY        VALUE
'   [0]     green      verde
'   [1]     red        rojo
'   [2]     blue       azul
'


[C#] 
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 in two different ways.
      Console.WriteLine( "Displays the elements using foreach:" );
      PrintKeysAndValues( myCol );
      Console.WriteLine( "Displays the elements using the Keys, Values, Count, and indexer properties:" );
      PrintKeysAndValues2( myCol );

   }

   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();
   }

   public static void PrintKeysAndValues2( StringDictionary myCol )  {
      String[] myKeys = new String[myCol.Count];
      myCol.Keys.CopyTo( myKeys, 0 );

      Console.WriteLine( "   [INDEX] KEY        VALUE" );
      for ( int i = 0; i < myCol.Count; i++ )
         Console.WriteLine( "   [{0}]     {1,-10} {2}", i, myKeys[i], myCol[myKeys[i]] );
      Console.WriteLine();
   }


}

/*
This code produces the following output.

Displays the elements using foreach:
   KEY        VALUE
   green      verde
   red        rojo
   blue       azul

Displays the elements using the Keys, Values, Count, and indexer properties:
   [INDEX] KEY        VALUE
   [0]     green      verde
   [1]     red        rojo
   [2]     blue       azul

*/

[C++] 
#using <mscorlib.dll>
#using <System.dll>
using namespace System;
using namespace System::Collections;
using namespace System::Collections::Specialized;

void PrintKeysAndValues( StringDictionary* myCol )  {
   Console::WriteLine( S"   KEY        VALUE" );
   IEnumerator* enum0 = myCol->GetEnumerator();
   while (enum0->MoveNext())
   {
      DictionaryEntry* de = __try_cast<DictionaryEntry*>(enum0->Current);
      Console::WriteLine( S"   {0,-10} {1}", de->Key, de->Value );
   }
   Console::WriteLine();
}

void PrintKeysAndValues2( StringDictionary* myCol )  {
   String* myKeys[] = static_cast<String*[]>( Array::CreateInstance( __typeof(String), myCol->Count ) );
   myCol->Keys->CopyTo( myKeys, 0 );

   Console::WriteLine( S"   [INDEX] KEY        VALUE" );
   for ( int i = 0; i < myCol->Count; i++ )
      Console::WriteLine( S"   [{0}]     {1,-10} {2}", __box(i), myKeys[i], myCol->Item[myKeys[i]] );
   Console::WriteLine();
}

int main()  {

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

   // Displays the values in the StringDictionary in two different ways.
   Console::WriteLine( S"Displays the elements using foreach:" );
   PrintKeysAndValues( myCol );
   Console::WriteLine( S"Displays the elements using the Keys, Values, Count, and indexer properties:" );
   PrintKeysAndValues2( myCol );

}

/*
This code produces the following output.

Displays the elements using foreach:
   KEY        VALUE
   green      verde
   red        rojo
   blue       azul

Displays the elements using the Keys, Values, Count, and indexer properties:
   [INDEX] KEY        VALUE
   [0]     green      verde
   [1]     red        rojo
   [2]     blue       azul

*/

[JScript] No example is available for JScript. To view a Visual Basic, C#, or C++ example, click the Language Filter button Language Filter in the upper-left corner of the page.

Requirements

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family

See Also

StringDictionary Class | StringDictionary Members | System.Collections.Specialized Namespace

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