NameObjectCollectionBase.BaseHasKeys Method ()

 
System_CAPS_noteNote

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Gets a value indicating whether the NameObjectCollectionBase instance contains entries whose keys are not null.

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

Protected Function BaseHasKeys As Boolean

Return Value

Type: System.Boolean

true if the NameObjectCollectionBase instance contains entries whose keys are not null; 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 null.

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 'NewNew

   ' 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

Universal Windows Platform
Available since 10
.NET Framework
Available since 1.1
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