Export (0) Print
Expand All
This topic has not yet been rated - Rate this topic

NameObjectCollectionBase.BaseHasKeys Method

Gets a value indicating whether the NameObjectCollectionBase instance contains entries whose keys are not a null reference (Nothing in Visual Basic).

Namespace: System.Collections.Specialized
Assembly: System (in system.dll)

'Declaration
Protected Function BaseHasKeys As Boolean
'Usage
Dim returnValue As Boolean

returnValue = Me.BaseHasKeys
protected boolean BaseHasKeys ()
protected function BaseHasKeys () : boolean
Not applicable.

Return Value

true if the NameObjectCollectionBase instance contains entries whose keys are not a null reference (Nothing in Visual Basic); otherwise, false.

This method is an O(1) operation.

The following code example uses BaseHasKeys to determine if the collection contains keys that are not a null reference (Nothing in 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

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

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

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

End Class 'MyCollection


Public Class SamplesNameObjectCollectionBase   

   Public Shared Sub Main()

      ' Creates an empty MyCollection instance.
      Dim myCol As New MyCollection()
      Console.WriteLine("Initial state of the collection (Count = {0}):", myCol.Count)
      PrintKeysAndValues(myCol)
      Console.WriteLine("HasKeys? {0}", myCol.HasKeys)

      Console.WriteLine()

      ' Adds an item to the collection.
      myCol.Add("blue", "sky")
      Console.WriteLine("Initial state of the collection (Count = {0}):", myCol.Count)
      PrintKeysAndValues(myCol)
      Console.WriteLine("HasKeys? {0}", myCol.HasKeys)

   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 = 0):
'HasKeys? False
'
'Initial state of the collection (Count = 1):
'[0] : blue, sky
'HasKeys? True


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

public class MyCollection extends NameObjectCollectionBase
{
    private DictionaryEntry _de =  new DictionaryEntry();

    // Gets a key-and-value pair (DictionaryEntry) using an index.
    /** @property 
     */
    public DictionaryEntry get_Item(int index)
    {
        _de.set_Key(this.BaseGetKey(index));
        _de.set_Value(this.BaseGet(index));
        return _de ;
    } //get_Item

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

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

    // Gets a value indicating whether the collection contains keys that are
    // not a null reference.
    /** @property 
     */
    public boolean get_HasKeys()
    {
        return this.BaseHasKeys() ;
    } //get_HasKeys
} //MyCollection


public class SamplesNameObjectCollectionBase
{
    public static void main(String[] args)
    {            
        // Creates an empty MyCollection instance.
        MyCollection myCol =  new MyCollection();
        Console.WriteLine("Initial state of the collection (Count = {0}):",
            System.Convert.ToString( myCol.get_Count()));
        PrintKeysAndValues(myCol);
        Console.WriteLine("HasKeys? {0}", 
            System.Convert.ToString(myCol.get_HasKeys()));
        Console.WriteLine();
        
        // Adds an item to the collection.
        myCol.Add("blue", "sky");
        Console.WriteLine("Initial state of the collection (Count = {0}):",
            System.Convert.ToString(myCol.get_Count()));
        PrintKeysAndValues(myCol);
        Console.WriteLine("HasKeys? {0}",
            System.Convert.ToString(myCol.get_HasKeys()));
    } //main

    public static void PrintKeysAndValues(MyCollection myCol) 
    {
        for (int i=0; i < myCol.get_Count(); i++) {        
            Console.WriteLine("[{0}] : {1}, {2}",System.Convert.ToString(i), 
                myCol.get_Item(i).get_Key(), myCol.get_Item(i).get_Value());
        } 
    } //PrintKeysAndValues
} //SamplesNameObjectCollectionBase
 
/*
This code produces the following output.

Initial state of the collection (Count = 0):
HasKeys? False

Initial state of the collection (Count = 1):
[0] : blue, sky
HasKeys? True

*/

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

XNA Framework

Supported in: 1.0

Community Additions

ADD
Show:
© 2014 Microsoft. All rights reserved.