DictionaryBase.GetEnumerator Method

Reference

Definition

Namespace:: System.Collections

Assemblies:: mscorlib.dll, System.Collections.NonGeneric.dll

Assembly:: System.Collections.NonGeneric.dll

Assembly:: mscorlib.dll

Assembly:: netstandard.dll

Source:: DictionaryBase.cs

Source:: DictionaryBase.cs

Source:: DictionaryBase.cs

Important

Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.

Returns an IDictionaryEnumerator that iterates through the DictionaryBase instance.

public:
 virtual System::Collections::IDictionaryEnumerator ^ GetEnumerator();

public System.Collections.IDictionaryEnumerator GetEnumerator ();

abstract member GetEnumerator : unit -> System.Collections.IDictionaryEnumerator
override this.GetEnumerator : unit -> System.Collections.IDictionaryEnumerator

Public Function GetEnumerator () As IDictionaryEnumerator

Returns

IDictionaryEnumerator

An IDictionaryEnumerator for the DictionaryBase instance.

Implements

GetEnumerator()

Examples

The following code example implements the DictionaryBase class and uses that implementation to create a dictionary of String keys and values that have a Length of 5 characters or less.

using namespace System;
using namespace System::Collections;

public ref class ShortStringDictionary: public DictionaryBase
{
public:

   property String^ Item [String^]
   {
      String^ get( String^ key )
      {
         return (dynamic_cast<String^>(Dictionary[ key ]));
      }

      void set( String^ value, String^ key )
      {
         Dictionary[ key ] = value;
      }
   }

   property ICollection^ Keys 
   {
      ICollection^ get()
      {
         return (Dictionary->Keys);
      }
   }

   property ICollection^ Values 
   {
      ICollection^ get()
      {
         return (Dictionary->Values);
      }
   }
   void Add( String^ key, String^ value )
   {
      Dictionary->Add( key, value );
   }

   bool Contains( String^ key )
   {
      return (Dictionary->Contains( key ));
   }

   void Remove( String^ key )
   {
      Dictionary->Remove( key );
   }


protected:
   virtual void OnInsert( Object^ key, Object^ value ) override
   {
      if ( key->GetType() != Type::GetType( "System.String" ) )
            throw gcnew ArgumentException( "key must be of type String.","key" );
      else
      {
         String^ strKey = dynamic_cast<String^>(key);
         if ( strKey->Length > 5 )
                  throw gcnew ArgumentException( "key must be no more than 5 characters in length.","key" );
      }

      if ( value->GetType() != Type::GetType( "System.String" ) )
            throw gcnew ArgumentException( "value must be of type String.","value" );
      else
      {
         String^ strValue = dynamic_cast<String^>(value);
         if ( strValue->Length > 5 )
                  throw gcnew ArgumentException( "value must be no more than 5 characters in length.","value" );
      }
   }

   virtual void OnRemove( Object^ key, Object^ /*value*/ ) override
   {
      if ( key->GetType() != Type::GetType( "System.String" ) )
            throw gcnew ArgumentException( "key must be of type String.","key" );
      else
      {
         String^ strKey = dynamic_cast<String^>(key);
         if ( strKey->Length > 5 )
                  throw gcnew ArgumentException( "key must be no more than 5 characters in length.","key" );
      }
   }

   virtual void OnSet( Object^ key, Object^ /*oldValue*/, Object^ newValue ) override
   {
      if ( key->GetType() != Type::GetType( "System.String" ) )
            throw gcnew ArgumentException( "key must be of type String.","key" );
      else
      {
         String^ strKey = dynamic_cast<String^>(key);
         if ( strKey->Length > 5 )
                  throw gcnew ArgumentException( "key must be no more than 5 characters in length.","key" );
      }

      if ( newValue->GetType() != Type::GetType( "System.String" ) )
            throw gcnew ArgumentException( "newValue must be of type String.","newValue" );
      else
      {
         String^ strValue = dynamic_cast<String^>(newValue);
         if ( strValue->Length > 5 )
                  throw gcnew ArgumentException( "newValue must be no more than 5 characters in length.","newValue" );
      }
   }

   virtual void OnValidate( Object^ key, Object^ value ) override
   {
      if ( key->GetType() != Type::GetType( "System.String" ) )
            throw gcnew ArgumentException( "key must be of type String.","key" );
      else
      {
         String^ strKey = dynamic_cast<String^>(key);
         if ( strKey->Length > 5 )
                  throw gcnew ArgumentException( "key must be no more than 5 characters in length.","key" );
      }

      if ( value->GetType() != Type::GetType( "System.String" ) )
            throw gcnew ArgumentException( "value must be of type String.","value" );
      else
      {
         String^ strValue = dynamic_cast<String^>(value);
         if ( strValue->Length > 5 )
                  throw gcnew ArgumentException( "value must be no more than 5 characters in length.","value" );
      }
   }

};

void PrintKeysAndValues2( ShortStringDictionary^ myCol );
void PrintKeysAndValues3( ShortStringDictionary^ myCol );
int main()
{
   // Creates and initializes a new DictionaryBase.
   ShortStringDictionary^ mySSC = gcnew 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 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 );
   }

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

   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\":" );
   PrintKeysAndValues2( mySSC );
}

// Uses the enumerator. 
void PrintKeysAndValues2( ShortStringDictionary^ myCol )
{
   DictionaryEntry myDE;
   System::Collections::IEnumerator^ myEnumerator = myCol->GetEnumerator();
   while ( myEnumerator->MoveNext() )
      if ( myEnumerator->Current != nullptr )
   {
      myDE =  *dynamic_cast<DictionaryEntry^>(myEnumerator->Current);
      Console::WriteLine( "   {0,-5} : {1}", myDE.Key, myDE.Value );
   }

   Console::WriteLine();
}


// Uses the Keys property and the Item property.
void PrintKeysAndValues3( ShortStringDictionary^ myCol )
{
   ICollection^ myKeys = myCol->Keys;
   IEnumerator^ myEnum1 = myKeys->GetEnumerator();
   while ( myEnum1->MoveNext() )
   {
      String^ k = safe_cast<String^>(myEnum1->Current);
      Console::WriteLine( "   {0,-5} : {1}", k, myCol->Item[ k ] );
   }

   Console::WriteLine();
}

/* 
This code produces the following output.

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

*/

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

*/

Imports System.Collections

Public Class ShortStringDictionary
   Inherits DictionaryBase

   Default Public Property Item(key As String) As String
      Get
         Return CType(Dictionary(key), String)
      End Get
      Set
         Dictionary(key) = value
      End Set
   End Property

   Public ReadOnly Property Keys() As ICollection
      Get
         Return Dictionary.Keys
      End Get
   End Property

   Public ReadOnly Property Values() As ICollection
      Get
         Return Dictionary.Values
      End Get
   End Property

   Public Sub Add(key As String, value As String)
      Dictionary.Add(key, value)
   End Sub

   Public Function Contains(key As String) As Boolean
      Return Dictionary.Contains(key)
   End Function 'Contains

   Public Sub Remove(key As String)
      Dictionary.Remove(key)
   End Sub

   Protected Overrides Sub OnInsert(key As Object, value As Object)
      If Not GetType(System.String).IsAssignableFrom(key.GetType()) Then
         Throw New ArgumentException("key must be of type String.", "key")
      Else
         Dim strKey As String = CType(key, String)
         If strKey.Length > 5 Then
            Throw New ArgumentException("key must be no more than 5 characters in length.", "key")
         End If
      End If 
      If Not GetType(System.String).IsAssignableFrom(value.GetType()) Then
         Throw New ArgumentException("value must be of type String.", "value")
      Else
         Dim strValue As String = CType(value, String)
         If strValue.Length > 5 Then
            Throw New ArgumentException("value must be no more than 5 characters in length.", "value")
         End If
      End If
   End Sub

   Protected Overrides Sub OnRemove(key As Object, value As Object)
      If Not GetType(System.String).IsAssignableFrom(key.GetType()) Then
         Throw New ArgumentException("key must be of type String.", "key")
      Else
         Dim strKey As String = CType(key, String)
         If strKey.Length > 5 Then
            Throw New ArgumentException("key must be no more than 5 characters in length.", "key")
         End If
      End If
   End Sub

   Protected Overrides Sub OnSet(key As Object, oldValue As Object, newValue As Object)
      If Not GetType(System.String).IsAssignableFrom(key.GetType()) Then
         Throw New ArgumentException("key must be of type String.", "key")
      Else
         Dim strKey As String = CType(key, String)
         If strKey.Length > 5 Then
            Throw New ArgumentException("key must be no more than 5 characters in length.", "key")
         End If
      End If 
      If Not GetType(System.String).IsAssignableFrom(newValue.GetType()) Then
         Throw New ArgumentException("newValue must be of type String.", "newValue")
      Else
         Dim strValue As String = CType(newValue, String)
         If strValue.Length > 5 Then
            Throw New ArgumentException("newValue must be no more than 5 characters in length.", "newValue")
         End If
      End If
   End Sub

   Protected Overrides Sub OnValidate(key As Object, value As Object)
      If Not GetType(System.String).IsAssignableFrom(key.GetType()) Then
         Throw New ArgumentException("key must be of type String.", "key")
      Else
         Dim strKey As String = CType(key, String)
         If strKey.Length > 5 Then
            Throw New ArgumentException("key must be no more than 5 characters in length.", "key")
         End If
      End If 
      If Not GetType(System.String).IsAssignableFrom(value.GetType()) Then
         Throw New ArgumentException("value must be of type String.", "value")
      Else
         Dim strValue As String = CType(value, String)
         If strValue.Length > 5 Then
            Throw New ArgumentException("value must be no more than 5 characters in length.", "value")
         End If
      End If
   End Sub

End Class


Public Class SamplesDictionaryBase

   Public Shared Sub Main()

      ' Creates and initializes a new DictionaryBase.
      Dim mySSC As 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 For Each. This is the preferred method.
      Console.WriteLine("Contents of the collection (using For Each):")
      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 e As ArgumentException
          Console.WriteLine(e.ToString())
      End Try

      ' Tries to add a key that is too long.
      Try
          mySSC.Add("Eleven", "ijk")
      Catch e As ArgumentException
          Console.WriteLine(e.ToString())
      End Try

      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)

    End Sub


    ' Uses the For Each statement which hides the complexity of the enumerator.
    ' NOTE: The For Each statement is the preferred way of enumerating the contents of a collection.
    Public Shared Sub PrintKeysAndValues1(myCol As ShortStringDictionary)
      Dim myDE As DictionaryEntry
      For Each myDE In  myCol
          Console.WriteLine("   {0,-5} : {1}", myDE.Key, myDE.Value)
      Next myDE
      Console.WriteLine()
    End Sub


    ' Uses the enumerator. 
    ' NOTE: The For Each statement is the preferred way of enumerating the contents of a collection.
    Public Shared Sub PrintKeysAndValues2(myCol As ShortStringDictionary)
      Dim myDE As DictionaryEntry
      Dim myEnumerator As System.Collections.IEnumerator = myCol.GetEnumerator()
      While myEnumerator.MoveNext()
          If Not (myEnumerator.Current Is Nothing) Then
            myDE = CType(myEnumerator.Current, DictionaryEntry)
            Console.WriteLine("   {0,-5} : {1}", myDE.Key, myDE.Value)
          End If
      End While
      Console.WriteLine()
    End Sub


    ' Uses the Keys property and the Item property.
    Public Shared Sub PrintKeysAndValues3(myCol As ShortStringDictionary)
      Dim myKeys As ICollection = myCol.Keys
      Dim k As String
      For Each k In  myKeys
          Console.WriteLine("   {0,-5} : {1}", k, myCol(k))
      Next k
      Console.WriteLine()
    End Sub

End Class


'This code produces the following output.
'
'Contents of the collection (using For Each):
'   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

Remarks

The foreach statement of the C# language (for each in Visual Basic) hides the complexity of the enumerators. Therefore, using foreach is recommended, instead of directly manipulating the enumerator.

Enumerators can be used to read the data in the collection, but they 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, Current is undefined. 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.

If MoveNext passes the end of the collection, the enumerator is positioned after the last element in the collection and MoveNext returns false. When the enumerator is at this position, subsequent calls to MoveNext also return false. If the last call to MoveNext returned false, Current is undefined. 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 its behavior is undefined.

The enumerator does not have exclusive access to the collection; therefore, enumerating through a collection is intrinsically not a thread-safe procedure. To guarantee thread safety during enumeration, you can lock the collection during the entire enumeration. To allow the collection to be accessed by multiple threads for reading and writing, you must implement your own synchronization.

This method is an O(1) operation.

Applies to

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