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NameObjectCollectionBase Class

Provides the abstract (MustInherit in Visual Basic) base class for a collection of associated String keys and Object values that can be accessed either with the key or with the index.

For a list of all members of this type, see NameObjectCollectionBase Members.

System.Object
   System.Collections.Specialized.NameObjectCollectionBase
      Derived classes

[Visual Basic]
<Serializable>
MustInherit Public Class NameObjectCollectionBase
   Implements ICollection, IEnumerable, ISerializable, _
   IDeserializationCallback
[C#]
[Serializable]
public abstract class NameObjectCollectionBase : ICollection,
   IEnumerable, ISerializable, IDeserializationCallback
[C++]
[Serializable]
public __gc __abstract class NameObjectCollectionBase : public
   ICollection, IEnumerable, ISerializable,
   IDeserializationCallback
[JScript]
public
   Serializable
abstract class NameObjectCollectionBase implements
   ICollection, IEnumerable, ISerializable,
   IDeserializationCallback

Thread Safety

Public static (Shared in Visual Basic) members of this type are safe for multithreaded operations. Instance members are not guaranteed to be thread-safe.

This implementation does not provide a synchronized (thread-safe) wrapper for a NameObjectCollectionBase, but derived classes can create their own synchronized versions of the NameObjectCollectionBase using the SyncRoot property.

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.

Remarks

The underlying structure for this class is a hashtable.

The capacity is the number of key-and-value pairs that the NameObjectCollectionBase instance can contain. The default initial capacity is zero. The capacity is automatically increased as required.

The hash code provider dispenses hash codes for keys in the NameObjectCollectionBase instance. The default hash code provider is the CaseInsensitiveHashCodeProvider.

The comparer determines whether two keys are equal. The default comparer is the CaseInsensitiveComparer.

In .NET Framework version 1.0, this class uses culture-sensitive string comparisons. However, in .NET Framework version 1.1 and later, this class uses CultureInfo.InvariantCulture when comparing strings. For more information about how culture affects comparisons and sorting, see Comparing and Sorting Data for a Specific Culture and Performing Culture-Insensitive String Operations.

A null reference (Nothing in Visual Basic) is allowed as a key or as a value.

CAUTION   The BaseGet method does not distinguish between a null reference (Nothing) which is returned because the specified key is not found and a null reference (Nothing) which is returned because the value associated with the key is a null reference (Nothing).

Example

[Visual Basic, C#, C++] The following code example shows how to implement and use the NameObjectCollectionBase class.

[Visual Basic] 
Imports System
Imports System.Collections
Imports System.Collections.Specialized

Public Class MyCollection
   Inherits NameObjectCollectionBase

   Private _de As New DictionaryEntry()

   ' Creates an empty collection.
   Public Sub New()
   End Sub 'New

   ' Adds elements from an IDictionary into the new collection.
   Public Sub New(d As IDictionary, bReadOnly As [Boolean])
      Dim de As DictionaryEntry
      For Each de In  d
         Me.BaseAdd(CType(de.Key, [String]), de.Value)
      Next de
      Me.IsReadOnly = bReadOnly
   End Sub 'New

   ' Gets a key-and-value pair (DictionaryEntry) using an index.
   Default Public ReadOnly Property Item(index As Integer) As DictionaryEntry
      Get
         _de.Key = Me.BaseGetKey(index)
         _de.Value = Me.BaseGet(index)
         Return _de
      End Get
   End Property

   ' Gets or sets the value associated with the specified key.
   Default Public Property Item(key As [String]) As [Object]
      Get
         Return Me.BaseGet(key)
      End Get
      Set
         Me.BaseSet(key, value)
      End Set
   End Property

   ' Gets a String array that contains all the keys in the collection.
   Public ReadOnly Property AllKeys() As [String]()
      Get
         Return Me.BaseGetAllKeys()
      End Get
   End Property

   ' Gets an Object array that contains all the values in the collection.
   Public ReadOnly Property AllValues() As Array
      Get
         Return Me.BaseGetAllValues()
      End Get
   End Property

   ' Gets a String array that contains all the values in the collection.
   Public ReadOnly Property AllStringValues() As [String]()
      Get
         Return CType(Me.BaseGetAllValues(Type.GetType("System.String")), [String]())
      End Get
   End Property

   ' Gets a value indicating if the collection contains keys that are not null.
   Public ReadOnly Property HasKeys() As [Boolean]
      Get
         Return Me.BaseHasKeys()
      End Get
   End Property

   ' Adds an entry to the collection.
   Public Sub Add(key As [String], value As [Object])
      Me.BaseAdd(key, value)
   End Sub 'Add

   ' Removes an entry with the specified key from the collection.
   Overloads Public Sub Remove(key As [String])
      Me.BaseRemove(key)
   End Sub 'Remove

   ' Removes an entry in the specified index from the collection.
   Overloads Public Sub Remove(index As Integer)
      Me.BaseRemoveAt(index)
   End Sub 'Remove

   ' Clears all the elements in the collection.
   Public Sub Clear()
      Me.BaseClear()
   End Sub 'Clear

End Class 'MyCollection


Public Class SamplesNameObjectCollectionBase   

   Public Shared Sub Main()

      ' Creates and initializes a new MyCollection that is read-only.
      Dim d = New ListDictionary()
      d.Add("red", "apple")
      d.Add("yellow", "banana")
      d.Add("green", "pear")
      Dim myROCol As New MyCollection(d, True)

      ' Tries to add a new item.
      Try
         myROCol.Add("blue", "sky")
      Catch e As NotSupportedException
         Console.WriteLine(e.ToString())
      End Try

      ' Displays the keys and values of the MyCollection.
      Console.WriteLine("Read-Only Collection:")
      PrintKeysAndValues(myROCol)

      ' Creates and initializes an empty MyCollection that is writable.
      Dim myRWCol As New MyCollection()

      ' Adds new items to the collection.
      myRWCol.Add("purple", "grape")
      myRWCol.Add("orange", "tangerine")
      myRWCol.Add("black", "berries")
      Console.WriteLine("Writable Collection (after adding values):")
      PrintKeysAndValues(myRWCol)

      ' Changes the value of one element.
      myRWCol("orange") = "grapefruit"
      Console.WriteLine("Writable Collection (after changing one value):")
      PrintKeysAndValues(myRWCol)

      ' Removes one item from the collection.
      myRWCol.Remove("black")
      Console.WriteLine("Writable Collection (after removing one value):")
      PrintKeysAndValues(myRWCol)

      ' Removes all elements from the collection.
      myRWCol.Clear()
      Console.WriteLine("Writable Collection (after clearing the collection):")
      PrintKeysAndValues(myRWCol)

   End Sub 'Main

   ' Prints the indexes, keys, and values.
   Public Shared Sub PrintKeysAndValues(myCol As MyCollection)
      Dim i As Integer
      For i = 0 To myCol.Count - 1
         Console.WriteLine("[{0}] : {1}, {2}", i, myCol(i).Key, myCol(i).Value)
      Next i
   End Sub 'PrintKeysAndValues

   ' Prints the keys and values using AllKeys.
   Public Shared Sub PrintKeysAndValues2(myCol As MyCollection)
      Dim s As [String]
      For Each s In  myCol.AllKeys
         Console.WriteLine("{0}, {1}", s, myCol(s))
      Next s
   End Sub 'PrintKeysAndValues2

End Class 'SamplesNameObjectCollectionBase


'This code produces the following output.
'
'System.NotSupportedException: Collection is read-only.
'   at System.Collections.Specialized.NameObjectCollectionBase.BaseAdd(String name, Object value)
'   at SamplesNameObjectCollectionBase.Main()
'Read-Only Collection:
'[0] : red, apple
'[1] : yellow, banana
'[2] : green, pear
'Writable Collection (after adding values):
'[0] : purple, grape
'[1] : orange, tangerine
'[2] : black, berries
'Writable Collection (after changing one value):
'[0] : purple, grape
'[1] : orange, grapefruit
'[2] : black, berries
'Writable Collection (after removing one value):
'[0] : purple, grape
'[1] : orange, grapefruit
'Writable Collection (after clearing the collection):


[C#] 
using System;
using System.Collections;
using System.Collections.Specialized;

public class MyCollection : NameObjectCollectionBase  {

   private DictionaryEntry _de = new DictionaryEntry();

   // Creates an empty collection.
   public MyCollection()  {
   }

   // Adds elements from an IDictionary into the new collection.
   public MyCollection( IDictionary d, Boolean bReadOnly )  {
      foreach ( DictionaryEntry de in d )  {
         this.BaseAdd( (String) de.Key, de.Value );
      }
      this.IsReadOnly = bReadOnly;
   }

   // Gets a key-and-value pair (DictionaryEntry) using an index.
   public DictionaryEntry this[ int index ]  {
      get  {
         _de.Key = this.BaseGetKey(index);
         _de.Value = this.BaseGet(index);
         return( _de );
      }
   }

   // Gets or sets the value associated with the specified key.
   public Object this[ String key ]  {
      get  {
         return( this.BaseGet( key ) );
      }
      set  {
         this.BaseSet( key, value );
      }
   }

   // Gets a String array that contains all the keys in the collection.
   public String[] AllKeys  {
      get  {
         return( this.BaseGetAllKeys() );
      }
   }

   // Gets an Object array that contains all the values in the collection.
   public Array AllValues  {
      get  {
         return( this.BaseGetAllValues() );
      }
   }

   // Gets a String array that contains all the values in the collection.
   public String[] AllStringValues  {
      get  {
         return( (String[]) this.BaseGetAllValues( Type.GetType( "System.String" ) ) );
      }
   }

   // Gets a value indicating if the collection contains keys that are not null.
   public Boolean HasKeys  {
      get  {
         return( this.BaseHasKeys() );
      }
   }

   // Adds an entry to the collection.
   public void Add( String key, Object value )  {
      this.BaseAdd( key, value );
   }

   // Removes an entry with the specified key from the collection.
   public void Remove( String key )  {
      this.BaseRemove( key );
   }

   // Removes an entry in the specified index from the collection.
   public void Remove( int index )  {
      this.BaseRemoveAt( index );
   }

   // Clears all the elements in the collection.
   public void Clear()  {
      this.BaseClear();
   }

}

public class SamplesNameObjectCollectionBase  {

   public static void Main()  {

      // Creates and initializes a new MyCollection that is read-only.
      IDictionary d = new ListDictionary();
      d.Add( "red", "apple" );
      d.Add( "yellow", "banana" );
      d.Add( "green", "pear" );
      MyCollection myROCol = new MyCollection( d, true );

      // Tries to add a new item.
      try  {
         myROCol.Add( "blue", "sky" );
      }
      catch ( NotSupportedException e )  {
         Console.WriteLine( e.ToString() );
      }

      // Displays the keys and values of the MyCollection.
      Console.WriteLine( "Read-Only Collection:" );
      PrintKeysAndValues( myROCol );


      // Creates and initializes an empty MyCollection that is writable.
      MyCollection myRWCol = new MyCollection();

      // Adds new items to the collection.
      myRWCol.Add( "purple", "grape" );
      myRWCol.Add( "orange", "tangerine" );
      myRWCol.Add( "black", "berries" );
      Console.WriteLine( "Writable Collection (after adding values):" );
      PrintKeysAndValues( myRWCol );

      // Changes the value of one element.
      myRWCol["orange"] = "grapefruit";
      Console.WriteLine( "Writable Collection (after changing one value):" );
      PrintKeysAndValues( myRWCol );

      // Removes one item from the collection.
      myRWCol.Remove( "black" );
      Console.WriteLine( "Writable Collection (after removing one value):" );
      PrintKeysAndValues( myRWCol );

      // Removes all elements from the collection.
      myRWCol.Clear();
      Console.WriteLine( "Writable Collection (after clearing the collection):" );
      PrintKeysAndValues( myRWCol );

   }

   // Prints the indexes, keys, and values.
   public static void PrintKeysAndValues( MyCollection myCol )  {
      for ( int i = 0; i < myCol.Count; i++ )  {
         Console.WriteLine( "[{0}] : {1}, {2}", i, myCol[i].Key, myCol[i].Value );
      }
   }

   // Prints the keys and values using AllKeys.
   public static void PrintKeysAndValues2( MyCollection myCol )  {
      foreach ( String s in myCol.AllKeys )  {
         Console.WriteLine( "{0}, {1}", s, myCol[s] );
      }
   }
}


/*
This code produces the following output.

System.NotSupportedException: Collection is read-only.
   at System.Collections.Specialized.NameObjectCollectionBase.BaseAdd(String name, Object value)
   at SamplesNameObjectCollectionBase.Main()
Read-Only Collection:
[0] : red, apple
[1] : yellow, banana
[2] : green, pear
Writable Collection (after adding values):
[0] : purple, grape
[1] : orange, tangerine
[2] : black, berries
Writable Collection (after changing one value):
[0] : purple, grape
[1] : orange, grapefruit
[2] : black, berries
Writable Collection (after removing one value):
[0] : purple, grape
[1] : orange, grapefruit
Writable Collection (after clearing the collection):

*/

[C++] 
#using <mscorlib.dll>
#using <system.dll>

using namespace System;
using namespace System::Collections;
using namespace System::Collections::Specialized;

public __gc class MyCollection : public NameObjectCollectionBase
{
private:
   DictionaryEntry _de;

public:
   // Creates an empty collection.
   MyCollection() 
   {
   }

   // Adds elements from an IDictionary* into the new collection.
   MyCollection(IDictionary* d, Boolean bReadOnly)
   {
      IEnumerator* myEnum = d->GetEnumerator();
      while (myEnum->MoveNext()) {
         DictionaryEntry* de = __try_cast<DictionaryEntry*>(myEnum->Current);

         this->BaseAdd(dynamic_cast<String*>(de->Key), de->Value);
      }
      this->IsReadOnly = bReadOnly;
   }

   // Gets a key-and-value pair (DictionaryEntry) using an index.
   __property DictionaryEntry* get_Item( int index )
   {
      _de.Key = this->BaseGetKey(index);
      _de.Value = this->BaseGet(index);
      return(__box(_de));
   }

   // Gets or sets the value associated with the specified key.
   __property Object* get_Item( String* key ) 
   {
      return(this->BaseGet(key));
   }
   __property void set_Item( String* key, Object* value )
   {
      this->BaseSet(key, value);
   }

   // Gets a String array that contains all the keys in the collection.
   __property String* get_AllKeys()[]
   {
      return(this->BaseGetAllKeys());
   }

   // Gets an Object array that contains all the values in the collection.
   __property Object* get_AllValues()[]
   {
      return(this->BaseGetAllValues());
   }

   // Gets a String array that contains all the values in the collection.
   __property String* get_AllStringValues()[]
   {
      return(dynamic_cast<String*[]>(this->BaseGetAllValues(Type::GetType(S"System::String"))));
   }

   // Gets a value indicating if the collection contains keys that are not 0.
   Boolean HasKeys()
   {
      return(this->BaseHasKeys());
   }

   // Adds an entry to the collection.
   void Add(String* key, Object* value)
   {
      this->BaseAdd(key, value);
   }

   // Removes an entry with the specified key from the collection.
   void Remove(String* key)
   {
      this->BaseRemove(key);
   }

   // Removes an entry in the specified index from the collection.
   void Remove(int index)
   {
      this->BaseRemoveAt(index);
   }

   // Clears all the elements in the collection.
   void Clear()
   {
      this->BaseClear();
   }

};

// Prints the indexes, keys, and values.
void PrintKeysAndValues(MyCollection* myCol) {
   for (int i = 0; i < myCol->Count; i++) {
      Console::WriteLine(S"->Item[ {0}] : {1}, {2}", __box(i), myCol->Item[i]->Key, myCol->Item[i]->Value);
   }
}

// Prints the keys and values using AllKeys.
void PrintKeysAndValues2(MyCollection* myCol)
{
   IEnumerator* myEnum = myCol->AllKeys->GetEnumerator();
   while (myEnum->MoveNext())
   {
      String* s = __try_cast<String*>(myEnum->Current);

      Console::WriteLine(S" {0}, {1}", s, myCol->Item[s]);
   }
}

int main() 
{
   // Creates and initializes a new MyCollection that is read-only.
   IDictionary* d = new ListDictionary();
   d->Add(S"red", S"apple");
   d->Add(S"yellow", S"banana");
   d->Add(S"green", S"pear");
   MyCollection* myROCol = new MyCollection(d, true);

   // Tries to add a new item.
   try
   {
      myROCol->Add(S"blue", S"sky");
   }
   catch (NotSupportedException* e)
   {
      Console::WriteLine(e);
   }

   // Displays the keys and values of the MyCollection.
   Console::WriteLine(S"Read-Only Collection:");
   PrintKeysAndValues(myROCol);

   // Creates and initializes an empty MyCollection that is writable.
   MyCollection* myRWCol = new MyCollection();

   // Adds new items to the collection.
   myRWCol->Add(S"purple", S"grape");
   myRWCol->Add(S"orange", S"tangerine");
   myRWCol->Add(S"black", S"berries");
   Console::WriteLine(S"Writable Collection (after adding values):");
   PrintKeysAndValues(myRWCol);

   // Changes the value of one element.
   myRWCol->Item[S"orange"] = S"grapefruit";
   Console::WriteLine(S"Writable Collection (after changing one value):");
   PrintKeysAndValues(myRWCol);

   // Removes one item from the collection.
   myRWCol->Remove(S"black");
   Console::WriteLine(S"Writable Collection (after removing one value):");
   PrintKeysAndValues(myRWCol);

   // Removes all elements from the collection.
   myRWCol->Clear();
   Console::WriteLine(S"Writable Collection (after clearing the collection):");
   PrintKeysAndValues(myRWCol);
}

/*
This code produces the following output.

System::NotSupportedException: Collection is read-only.
   at System::Collections::Specialized::NameObjectCollectionBase.BaseAdd(String name, Object value)
   at SamplesNameObjectCollectionBase::Main()
Read-Only Collection:
[0] : red, apple
[1] : yellow, banana
[2] : green, pear
Writable Collection (after adding values):
[0] : purple, grape
[1] : orange, tangerine
[2] : black, berries
Writable Collection (after changing one value):
[0] : purple, grape
[1] : orange, grapefruit
[2] : black, berries
Writable Collection (after removing one value):
[0] : purple, grape
[1] : orange, grapefruit
Writable Collection (after clearing the collection):

*/

[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

Namespace: System.Collections.Specialized

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

Assembly: System (in System.dll)

See Also

NameObjectCollectionBase Members | System.Collections.Specialized Namespace | Hashtable | NameValueCollection | String | Performing Culture-Insensitive String Operations

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