NameObjectCollectionBase Class
Provides the abstract (MustInherit in Visual Basic) base class for a collection of associated String keys and Object values that can be accessed either with the key or with the index.
For a list of all members of this type, see NameObjectCollectionBase Members.
System.Object
System.Collections.Specialized.NameObjectCollectionBase
Derived classes
[Visual Basic] <Serializable> MustInherit Public Class NameObjectCollectionBase Implements ICollection, IEnumerable, ISerializable, _ IDeserializationCallback [C#] [Serializable] public abstract class NameObjectCollectionBase : ICollection, IEnumerable, ISerializable, IDeserializationCallback [C++] [Serializable] public __gc __abstract class NameObjectCollectionBase : public ICollection, IEnumerable, ISerializable, IDeserializationCallback [JScript] public Serializable abstract class NameObjectCollectionBase implements ICollection, IEnumerable, ISerializable, IDeserializationCallback
Thread Safety
Public static (Shared in Visual Basic) members of this type are safe for multithreaded operations. 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 could 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.
Remarks
The underlying structure for this class is a hashtable.
The capacity is the number of key-and-value pairs that the NameObjectCollectionBase instance can contain. The default initial capacity is zero. The capacity is automatically increased as required.
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 and Performing Culture-Insensitive String Operations.
A null reference (Nothing in Visual Basic) is allowed as a key or as a value.
CAUTION The BaseGet method does not distinguish between a null reference (Nothing) which is returned because the specified key is not found and a null reference (Nothing) which is returned because the value associated with the key is a null reference (Nothing).
Example
[Visual Basic, C#, C++] The following code example shows how to implement and use the NameObjectCollectionBase class.
[Visual Basic] Imports System Imports System.Collections Imports System.Collections.Specialized Public Class MyCollection Inherits NameObjectCollectionBase Private _de As New DictionaryEntry() ' 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 _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 ' 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(Type.GetType("System.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 = 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): [C#] using System; using System.Collections; using System.Collections.Specialized; public class MyCollection : NameObjectCollectionBase { private DictionaryEntry _de = new DictionaryEntry(); // Creates an empty collection. public MyCollection() { } // Adds elements from an IDictionary into the new collection. public MyCollection( IDictionary d, Boolean bReadOnly ) { foreach ( DictionaryEntry de in d ) { this.BaseAdd( (String) de.Key, de.Value ); } this.IsReadOnly = bReadOnly; } // 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 ); } } // Gets a String array that contains all the keys in the collection. public String[] AllKeys { get { return( this.BaseGetAllKeys() ); } } // Gets an Object array that contains all the values in the collection. public Array AllValues { get { return( this.BaseGetAllValues() ); } } // Gets a String array that contains all the values in the collection. public String[] AllStringValues { get { return( (String[]) this.BaseGetAllValues( Type.GetType( "System.String" ) ) ); } } // Gets a value indicating if the collection contains keys that are not null. public Boolean HasKeys { get { return( this.BaseHasKeys() ); } } // Adds an entry to the collection. public void Add( String key, Object value ) { this.BaseAdd( key, value ); } // Removes an entry with the specified key from the collection. public void Remove( String key ) { this.BaseRemove( key ); } // Removes an entry in the specified index from the collection. public void Remove( int index ) { this.BaseRemoveAt( index ); } // Clears all the elements in the collection. public void Clear() { this.BaseClear(); } } public class SamplesNameObjectCollectionBase { public static void Main() { // Creates and initializes a new MyCollection that is read-only. IDictionary d = new ListDictionary(); d.Add( "red", "apple" ); d.Add( "yellow", "banana" ); d.Add( "green", "pear" ); MyCollection myROCol = new MyCollection( d, true ); // Tries to add a new item. try { myROCol.Add( "blue", "sky" ); } catch ( NotSupportedException e ) { Console.WriteLine( e.ToString() ); } // Displays the keys and values of the MyCollection. Console.WriteLine( "Read-Only Collection:" ); PrintKeysAndValues( myROCol ); // Creates and initializes an empty MyCollection that is writable. MyCollection myRWCol = 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 ); } // Prints the indexes, keys, and values. 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 ); } } // Prints the keys and values using AllKeys. public static void PrintKeysAndValues2( MyCollection myCol ) { foreach ( String s in myCol.AllKeys ) { Console.WriteLine( "{0}, {1}", s, myCol[s] ); } } } /* 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): */ [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; public: // Creates an empty collection. MyCollection() { } // Adds elements from an IDictionary* into the new collection. MyCollection(IDictionary* d, Boolean bReadOnly) { IEnumerator* myEnum = d->GetEnumerator(); while (myEnum->MoveNext()) { DictionaryEntry* de = __try_cast<DictionaryEntry*>(myEnum->Current); this->BaseAdd(dynamic_cast<String*>(de->Key), de->Value); } this->IsReadOnly = bReadOnly; } // Gets a key-and-value pair (DictionaryEntry) using an index. __property DictionaryEntry* get_Item( int index ) { _de.Key = this->BaseGetKey(index); _de.Value = this->BaseGet(index); return(__box(_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); } // Gets a String array that contains all the keys in the collection. __property String* get_AllKeys()[] { return(this->BaseGetAllKeys()); } // Gets an Object array that contains all the values in the collection. __property Object* get_AllValues()[] { return(this->BaseGetAllValues()); } // Gets a String array that contains all the values in the collection. __property String* get_AllStringValues()[] { return(dynamic_cast<String*[]>(this->BaseGetAllValues(Type::GetType(S"System::String")))); } // Gets a value indicating if the collection contains keys that are not 0. Boolean HasKeys() { return(this->BaseHasKeys()); } // Adds an entry to the collection. void Add(String* key, Object* value) { this->BaseAdd(key, value); } // Removes an entry with the specified key from the collection. void Remove(String* key) { this->BaseRemove(key); } // Removes an entry in the specified index from the collection. void Remove(int index) { this->BaseRemoveAt(index); } // Clears all the elements in the collection. void Clear() { this->BaseClear(); } }; // Prints the indexes, keys, and values. void PrintKeysAndValues(MyCollection* myCol) { for (int i = 0; i < myCol->Count; i++) { Console::WriteLine(S"->Item[ {0}] : {1}, {2}", __box(i), myCol->Item[i]->Key, myCol->Item[i]->Value); } } // Prints the keys and values using AllKeys. void PrintKeysAndValues2(MyCollection* myCol) { IEnumerator* myEnum = myCol->AllKeys->GetEnumerator(); while (myEnum->MoveNext()) { String* s = __try_cast<String*>(myEnum->Current); Console::WriteLine(S" {0}, {1}", s, myCol->Item[s]); } } int main() { // Creates and initializes a new MyCollection that is read-only. IDictionary* d = new ListDictionary(); d->Add(S"red", S"apple"); d->Add(S"yellow", S"banana"); d->Add(S"green", S"pear"); MyCollection* myROCol = new MyCollection(d, true); // Tries to add a new item. try { myROCol->Add(S"blue", S"sky"); } catch (NotSupportedException* e) { Console::WriteLine(e); } // Displays the keys and values of the MyCollection. Console::WriteLine(S"Read-Only Collection:"); PrintKeysAndValues(myROCol); // Creates and initializes an empty MyCollection that is writable. MyCollection* myRWCol = new MyCollection(); // Adds new items to the collection. myRWCol->Add(S"purple", S"grape"); myRWCol->Add(S"orange", S"tangerine"); myRWCol->Add(S"black", S"berries"); Console::WriteLine(S"Writable Collection (after adding values):"); PrintKeysAndValues(myRWCol); // Changes the value of one element. myRWCol->Item[S"orange"] = S"grapefruit"; Console::WriteLine(S"Writable Collection (after changing one value):"); PrintKeysAndValues(myRWCol); // Removes one item from the collection. myRWCol->Remove(S"black"); Console::WriteLine(S"Writable Collection (after removing one value):"); PrintKeysAndValues(myRWCol); // Removes all elements from the collection. myRWCol->Clear(); Console::WriteLine(S"Writable Collection (after clearing the collection):"); PrintKeysAndValues(myRWCol); } /* 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): */
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Requirements
Namespace: System.Collections.Specialized
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
Assembly: System (in System.dll)
See Also
NameObjectCollectionBase Members | System.Collections.Specialized Namespace | Hashtable | NameValueCollection | String | Performing Culture-Insensitive String Operations