NameObjectCollectionBase Class
Assembly: System (in System.dll)
The underlying structure for this class is a hash table.
Each element is a key/value pair.
The capacity of a NameObjectCollectionBase is the number of elements the NameObjectCollectionBase can hold. As elements are added to a NameObjectCollectionBase, the capacity is automatically increased as required through reallocation.
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 Comparing and Sorting Data for a Specific Cultureand Performing Culture-Insensitive String Operations.
Nothing is allowed as a key or as a value.
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The BaseGet method does not distinguish between Nothing which is returned because the specified key is not found and Nothing which is returned because the value associated with the key is Nothing. |
The following code example shows how to implement and use the NameObjectCollectionBase class.
Imports System Imports System.Collections Imports System.Collections.Specialized Public Class MyCollection Inherits NameObjectCollectionBase ' 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 return new DictionaryEntry( _ me.BaseGetKey(index), me.BaseGet(index) ) 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(GetType(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 As 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):
System.Collections.Specialized.NameObjectCollectionBase
System.Collections.Specialized.NameValueCollection
System.Configuration.ConfigurationSectionCollection
System.Configuration.ConfigurationSectionGroupCollection
System.Configuration.PropertyInformationCollection
System.Management.ManagementNamedValueCollection
System.Web.Configuration.VirtualDirectoryMappingCollection
System.Web.HttpApplicationState
System.Web.HttpCookieCollection
System.Web.HttpFileCollection
System.Web.HttpModuleCollection
System.Web.SessionState.SessionStateItemCollection
Public static (Shared in Visual Basic) members of this type are thread safe. Any 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 can 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.
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
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