NameObjectCollectionBase.BaseHasKeys Method ()
.NET Framework (current version)
Gets a value indicating whether the NameObjectCollectionBase instance contains entries whose keys are not null.
Assembly: System (in System.dll)
Return Value
Type: System.Booleantrue 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
Available since 10
.NET Framework
Available since 1.1
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