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NameObjectCollectionBase.BaseGetKey Method

Gets the key of the entry at the specified index of the NameObjectCollectionBase instance.

[Visual Basic]
Protected Function BaseGetKey( _
   ByVal index As Integer _
) As String
[C#]
protected string BaseGetKey(
 int index
);
[C++]
protected: String* BaseGetKey(
 int index
);
[JScript]
protected function BaseGetKey(
   index : int
) : String;

Parameters

index
The zero-based index of the key to get.

Return Value

A String that represents the key of the entry at the specified index.

Exceptions

Exception Type Condition
ArgumentOutOfRangeException index is outside the valid range of indexes for the collection.

Example

[Visual Basic, C#, C++] The following code example uses BaseGetKey and BaseGet to get specific keys and values.

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

Public Class MyCollection
   Inherits NameObjectCollectionBase

   Private _de As New DictionaryEntry()

   ' 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

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

End Class 'MyCollection


Public Class SamplesNameObjectCollectionBase   

   Public Shared Sub Main()

      ' Creates and initializes a new MyCollection instance.
      Dim d = New ListDictionary()
      d.Add("red", "apple")
      d.Add("yellow", "banana")
      d.Add("green", "pear")
      Dim myCol As New MyCollection(d)
      Console.WriteLine("Initial state of the collection (Count = {0}):", myCol.Count)
      PrintKeysAndValues(myCol)

      ' Gets specific keys and values.
      Console.WriteLine("The key at index 0 is {0}.", myCol(0).Key)
      Console.WriteLine("The value at index 0 is {0}.", myCol(0).Value)
      Console.WriteLine("The value associated with the key ""green"" is {0}.", myCol("green"))

   End Sub 'Main

   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

End Class 'SamplesNameObjectCollectionBase 


'This code produces the following output.
'
'Initial state of the collection (Count = 3):
'[0] : red, apple
'[1] : yellow, banana
'[2] : green, pear
'The key at index 0 is red.
'The value at index 0 is apple.
'The value associated with the key "green" is pear.


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

public class MyCollection : NameObjectCollectionBase  {

   private DictionaryEntry _de = new DictionaryEntry();

   // 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 );
      }
   }

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

}

public class SamplesNameObjectCollectionBase  {

   public static void Main()  {

      // Creates and initializes a new MyCollection instance.
      IDictionary d = new ListDictionary();
      d.Add( "red", "apple" );
      d.Add( "yellow", "banana" );
      d.Add( "green", "pear" );
      MyCollection myCol = new MyCollection( d );
      Console.WriteLine( "Initial state of the collection (Count = {0}):", myCol.Count );
      PrintKeysAndValues( myCol );

      // Gets specific keys and values.
      Console.WriteLine( "The key at index 0 is {0}.", myCol[0].Key );
      Console.WriteLine( "The value at index 0 is {0}.", myCol[0].Value );
      Console.WriteLine( "The value associated with the key \"green\" is {0}.", myCol["green"] );

   }

   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 );
      }
   }

}


/*
This code produces the following output.

Initial state of the collection (Count = 3):
[0] : red, apple
[1] : yellow, banana
[2] : green, pear
The key at index 0 is red.
The value at index 0 is apple.
The value associated with the key "green" is pear.

*/

[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;

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

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

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

int main() 
{
   // Creates and initializes a new MyCollection instance.
   IDictionary* d = new ListDictionary();
   d->Add(S"red", S"apple");
   d->Add(S"yellow", S"banana");
   d->Add(S"green", S"pear");
   MyCollection* myCol = new MyCollection(d);
   Console::WriteLine(S"Initial state of the collection (Count = {0}):", __box(myCol->Count));
   PrintKeysAndValues(myCol);

   // Gets specific keys and values.
   Console::WriteLine(S"The key at index 0 is {0}.", myCol->Item[0].Key);
   Console::WriteLine(S"The value at index 0 is {0}.", myCol->Item[0].Value);
   Console::WriteLine(S"The value associated with the key \"green\" is {0}.", myCol->Item[S"green"]);
}

/*
This code produces the following output.

Initial state of the collection (Count = 3):
[0] : red, apple
[1] : yellow, banana
[2] : green, pear
The key at index 0 is red.
The value at index 0 is apple.
The value associated with the key S"green" is pear.

*/

[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, .NET Compact Framework

See Also

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

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