Provides the abstract base class for a strongly typed collection.
Namespace:
System.Collections
Assembly:
mscorlib (in mscorlib.dll)
Visual Basic (Declaration)
<SerializableAttribute> _
<ComVisibleAttribute(True)> _
Public MustInherit Class CollectionBase _
Implements IList, ICollection, IEnumerable
Dim instance As CollectionBase
[SerializableAttribute]
[ComVisibleAttribute(true)]
public abstract class CollectionBase : IList,
ICollection, IEnumerable
[SerializableAttribute]
[ComVisibleAttribute(true)]
public ref class CollectionBase abstract : IList,
ICollection, IEnumerable
public abstract class CollectionBase implements IList, ICollection, IEnumerable
A CollectionBase instance is always modifiable. See ReadOnlyCollectionBase for a read-only version of this class.
The capacity of a CollectionBase is the number of elements the CollectionBase can hold. As elements are added to a CollectionBase, the capacity is automatically increased as required through reallocation. The capacity can be decreased by setting the Capacity property explicitly.
Notes to Implementers: This base class is provided to make it easier for implementers to create a strongly typed custom collection. Implementers are encouraged to extend this base class instead of creating their own.
The following code example implements the CollectionBase class and uses that implementation to create a collection of Int16 objects.
Imports System
Imports System.Collections
Public Class Int16Collection
Inherits CollectionBase
Default Public Property Item(index As Integer) As Int16
Get
Return CType(List(index), Int16)
End Get
Set
List(index) = value
End Set
End Property
Public Function Add(value As Int16) As Integer
Return List.Add(value)
End Function 'Add
Public Function IndexOf(value As Int16) As Integer
Return List.IndexOf(value)
End Function 'IndexOf
Public Sub Insert(index As Integer, value As Int16)
List.Insert(index, value)
End Sub 'Insert
Public Sub Remove(value As Int16)
List.Remove(value)
End Sub 'Remove
Public Function Contains(value As Int16) As Boolean
' If value is not of type Int16, this will return false.
Return List.Contains(value)
End Function 'Contains
Protected Overrides Sub OnInsert(index As Integer, value As Object)
' Insert additional code to be run only when inserting values.
End Sub 'OnInsert
Protected Overrides Sub OnRemove(index As Integer, value As Object)
' Insert additional code to be run only when removing values.
End Sub 'OnRemove
Protected Overrides Sub OnSet(index As Integer, oldValue As Object, newValue As Object)
' Insert additional code to be run only when setting values.
End Sub 'OnSet
Protected Overrides Sub OnValidate(value As Object)
If Not GetType(System.Int16).IsAssignableFrom(value.GetType()) Then
Throw New ArgumentException("value must be of type Int16.", "value")
End If
End Sub 'OnValidate
End Class 'Int16Collection
Public Class SamplesCollectionBase
Public Shared Sub Main()
' Creates and initializes a new CollectionBase.
Dim myI16 As New Int16Collection()
' Adds elements to the collection.
myI16.Add( 1 )
myI16.Add( 2 )
myI16.Add( 3 )
myI16.Add( 5 )
myI16.Add( 7 )
' Display the contents of the collection using For Each. This is the preferred method.
Console.WriteLine("Contents of the collection (using For Each):")
PrintValues1(myI16)
' Display the contents of the collection using the enumerator.
Console.WriteLine("Contents of the collection (using enumerator):")
PrintValues2(myI16)
' Display the contents of the collection using the Count property and the Item property.
Console.WriteLine("Initial contents of the collection (using Count and Item):")
PrintIndexAndValues(myI16)
' Searches the collection with Contains and IndexOf.
Console.WriteLine("Contains 3: {0}", myI16.Contains(3))
Console.WriteLine("2 is at index {0}.", myI16.IndexOf(2))
Console.WriteLine()
' Inserts an element into the collection at index 3.
myI16.Insert(3, 13)
Console.WriteLine("Contents of the collection after inserting at index 3:")
PrintIndexAndValues(myI16)
' Gets and sets an element using the index.
myI16(4) = 123
Console.WriteLine("Contents of the collection after setting the element at index 4 to 123:")
PrintIndexAndValues(myI16)
' Removes an element from the collection.
myI16.Remove(2)
' Display the contents of the collection using the Count property and the Item property.
Console.WriteLine("Contents of the collection after removing the element 2:")
PrintIndexAndValues(myI16)
End Sub 'Main
' Uses the Count property and the Item property.
Public Shared Sub PrintIndexAndValues(myCol As Int16Collection)
Dim i As Integer
For i = 0 To myCol.Count - 1
Console.WriteLine(" [{0}]: {1}", i, myCol(i))
Next i
Console.WriteLine()
End Sub 'PrintIndexAndValues
' Uses the For Each statement which hides the complexity of the enumerator.
' NOTE: The For Each statement is the preferred way of enumerating the contents of a collection.
Public Shared Sub PrintValues1(myCol As Int16Collection)
Dim i16 As Int16
For Each i16 In myCol
Console.WriteLine(" {0}", i16)
Next i16
Console.WriteLine()
End Sub 'PrintValues1
' Uses the enumerator.
' NOTE: The For Each statement is the preferred way of enumerating the contents of a collection.
Public Shared Sub PrintValues2(myCol As Int16Collection)
Dim myEnumerator As System.Collections.IEnumerator = myCol.GetEnumerator()
While myEnumerator.MoveNext()
Console.WriteLine(" {0}", myEnumerator.Current)
End While
Console.WriteLine()
End Sub 'PrintValues2
End Class 'SamplesCollectionBase
'This code produces the following output.
'
'Contents of the collection (using For Each):
' 1
' 2
' 3
' 5
' 7
'
'Contents of the collection (using enumerator):
' 1
' 2
' 3
' 5
' 7
'
'Initial contents of the collection (using Count and Item):
' [0]: 1
' [1]: 2
' [2]: 3
' [3]: 5
' [4]: 7
'
'Contains 3: True
'2 is at index 1.
'
'Contents of the collection after inserting at index 3:
' [0]: 1
' [1]: 2
' [2]: 3
' [3]: 13
' [4]: 5
' [5]: 7
'
'Contents of the collection after setting the element at index 4 to 123:
' [0]: 1
' [1]: 2
' [2]: 3
' [3]: 13
' [4]: 123
' [5]: 7
'
'Contents of the collection after removing the element 2:
' [0]: 1
' [1]: 3
' [2]: 13
' [3]: 123
' [4]: 7
using System;
using System.Collections;
public class Int16Collection : CollectionBase {
public Int16 this[ int index ] {
get {
return( (Int16) List[index] );
}
set {
List[index] = value;
}
}
public int Add( Int16 value ) {
return( List.Add( value ) );
}
public int IndexOf( Int16 value ) {
return( List.IndexOf( value ) );
}
public void Insert( int index, Int16 value ) {
List.Insert( index, value );
}
public void Remove( Int16 value ) {
List.Remove( value );
}
public bool Contains( Int16 value ) {
// If value is not of type Int16, this will return false.
return( List.Contains( value ) );
}
protected override void OnInsert( int index, Object value ) {
// Insert additional code to be run only when inserting values.
}
protected override void OnRemove( int index, Object value ) {
// Insert additional code to be run only when removing values.
}
protected override void OnSet( int index, Object oldValue, Object newValue ) {
// Insert additional code to be run only when setting values.
}
protected override void OnValidate( Object value ) {
if ( value.GetType() != typeof(System.Int16) )
throw new ArgumentException( "value must be of type Int16.", "value" );
}
}
public class SamplesCollectionBase {
public static void Main() {
// Create and initialize a new CollectionBase.
Int16Collection myI16 = new Int16Collection();
// Add elements to the collection.
myI16.Add( (Int16) 1 );
myI16.Add( (Int16) 2 );
myI16.Add( (Int16) 3 );
myI16.Add( (Int16) 5 );
myI16.Add( (Int16) 7 );
// Display the contents of the collection using foreach. This is the preferred method.
Console.WriteLine( "Contents of the collection (using foreach):" );
PrintValues1( myI16 );
// Display the contents of the collection using the enumerator.
Console.WriteLine( "Contents of the collection (using enumerator):" );
PrintValues2( myI16 );
// Display the contents of the collection using the Count property and the Item property.
Console.WriteLine( "Initial contents of the collection (using Count and Item):" );
PrintIndexAndValues( myI16 );
// Search the collection with Contains and IndexOf.
Console.WriteLine( "Contains 3: {0}", myI16.Contains( 3 ) );
Console.WriteLine( "2 is at index {0}.", myI16.IndexOf( 2 ) );
Console.WriteLine();
// Insert an element into the collection at index 3.
myI16.Insert( 3, (Int16) 13 );
Console.WriteLine( "Contents of the collection after inserting at index 3:" );
PrintIndexAndValues( myI16 );
// Get and set an element using the index.
myI16[4] = 123;
Console.WriteLine( "Contents of the collection after setting the element at index 4 to 123:" );
PrintIndexAndValues( myI16 );
// Remove an element from the collection.
myI16.Remove( (Int16) 2 );
// Display the contents of the collection using the Count property and the Item property.
Console.WriteLine( "Contents of the collection after removing the element 2:" );
PrintIndexAndValues( myI16 );
}
// Uses the Count property and the Item property.
public static void PrintIndexAndValues( Int16Collection myCol ) {
for ( int i = 0; i < myCol.Count; i++ )
Console.WriteLine( " [{0}]: {1}", i, myCol[i] );
Console.WriteLine();
}
// Uses the foreach statement which hides the complexity of the enumerator.
// NOTE: The foreach statement is the preferred way of enumerating the contents of a collection.
public static void PrintValues1( Int16Collection myCol ) {
foreach ( Int16 i16 in myCol )
Console.WriteLine( " {0}", i16 );
Console.WriteLine();
}
// Uses the enumerator.
// NOTE: The foreach statement is the preferred way of enumerating the contents of a collection.
public static void PrintValues2( Int16Collection myCol ) {
System.Collections.IEnumerator myEnumerator = myCol.GetEnumerator();
while ( myEnumerator.MoveNext() )
Console.WriteLine( " {0}", myEnumerator.Current );
Console.WriteLine();
}
}
/*
This code produces the following output.
Contents of the collection (using foreach):
1
2
3
5
7
Contents of the collection (using enumerator):
1
2
3
5
7
Initial contents of the collection (using Count and Item):
[0]: 1
[1]: 2
[2]: 3
[3]: 5
[4]: 7
Contains 3: True
2 is at index 1.
Contents of the collection after inserting at index 3:
[0]: 1
[1]: 2
[2]: 3
[3]: 13
[4]: 5
[5]: 7
Contents of the collection after setting the element at index 4 to 123:
[0]: 1
[1]: 2
[2]: 3
[3]: 13
[4]: 123
[5]: 7
Contents of the collection after removing the element 2:
[0]: 1
[1]: 3
[2]: 13
[3]: 123
[4]: 7
*/
#using <System.dll>
using namespace System;
using namespace System::Collections;
public ref class Int16Collection: public CollectionBase
{
public:
property Int16 Item [int]
{
Int16 get( int index )
{
return ( (Int16)(List[ index ]));
}
void set( int index, Int16 value )
{
List[ index ] = value;
}
}
int Add( Int16 value )
{
return (List->Add( value ));
}
int IndexOf( Int16 value )
{
return (List->IndexOf( value ));
}
void Insert( int index, Int16 value )
{
List->Insert( index, value );
}
void Remove( Int16 value )
{
List->Remove( value );
}
bool Contains( Int16 value )
{
// If value is not of type Int16, this will return false.
return (List->Contains( value ));
}
protected:
virtual void OnInsert( int /*index*/, Object^ /*value*/ ) override
{
// Insert additional code to be run only when inserting values.
}
virtual void OnRemove( int /*index*/, Object^ /*value*/ ) override
{
// Insert additional code to be run only when removing values.
}
virtual void OnSet( int /*index*/, Object^ /*oldValue*/, Object^ /*newValue*/ ) override
{
// Insert additional code to be run only when setting values.
}
virtual void OnValidate( Object^ value ) override
{
if ( value->GetType() != Type::GetType( "System.Int16" ) )
throw gcnew ArgumentException( "value must be of type Int16.","value" );
}
};
void PrintIndexAndValues( Int16Collection^ myCol );
void PrintValues2( Int16Collection^ myCol );
int main()
{
// Create and initialize a new CollectionBase.
Int16Collection^ myI16 = gcnew Int16Collection;
// Add elements to the collection.
myI16->Add( (Int16)1 );
myI16->Add( (Int16)2 );
myI16->Add( (Int16)3 );
myI16->Add( (Int16)5 );
myI16->Add( (Int16)7 );
// Display the contents of the collection using the enumerator.
Console::WriteLine( "Contents of the collection (using enumerator):" );
PrintValues2( myI16 );
// Display the contents of the collection using the Count property and the Item property.
Console::WriteLine( "Initial contents of the collection (using Count and Item):" );
PrintIndexAndValues( myI16 );
// Search the collection with Contains and IndexOf.
Console::WriteLine( "Contains 3: {0}", myI16->Contains( 3 ) );
Console::WriteLine( "2 is at index {0}.", myI16->IndexOf( 2 ) );
Console::WriteLine();
// Insert an element into the collection at index 3.
myI16->Insert( 3, (Int16)13 );
Console::WriteLine( "Contents of the collection after inserting at index 3:" );
PrintIndexAndValues( myI16 );
// Get and set an element using the index.
myI16->Item[ 4 ] = 123;
Console::WriteLine( "Contents of the collection after setting the element at index 4 to 123:" );
PrintIndexAndValues( myI16 );
// Remove an element from the collection.
myI16->Remove( (Int16)2 );
// Display the contents of the collection using the Count property and the Item property.
Console::WriteLine( "Contents of the collection after removing the element 2:" );
PrintIndexAndValues( myI16 );
}
// Uses the Count property and the Item property.
void PrintIndexAndValues( Int16Collection^ myCol )
{
for ( int i = 0; i < myCol->Count; i++ )
Console::WriteLine( " [{0}]: {1}", i, myCol->Item[ i ] );
Console::WriteLine();
}
// Uses the enumerator.
void PrintValues2( Int16Collection^ myCol )
{
System::Collections::IEnumerator^ myEnumerator = myCol->GetEnumerator();
while ( myEnumerator->MoveNext() )
Console::WriteLine( " {0}", myEnumerator->Current );
Console::WriteLine();
}
/*
This code produces the following output.
Contents of the collection (using enumerator):
1
2
3
5
7
Initial contents of the collection (using Count and Item):
[0]: 1
[1]: 2
[2]: 3
[3]: 5
[4]: 7
Contains 3: True
2 is at index 1.
Contents of the collection after inserting at index 3:
[0]: 1
[1]: 2
[2]: 3
[3]: 13
[4]: 5
[5]: 7
Contents of the collection after setting the element at index 4 to 123:
[0]: 1
[1]: 2
[2]: 3
[3]: 13
[4]: 123
[5]: 7
Contents of the collection after removing the element 2:
[0]: 1
[1]: 3
[2]: 13
[3]: 123
[4]: 7
*/
System..::.Object
System.Collections..::.CollectionBase
Microsoft.ManagementConsole..::.BaseCollection
System.CodeDom..::.CodeAttributeArgumentCollection
System.CodeDom..::.CodeAttributeDeclarationCollection
System.CodeDom..::.CodeCatchClauseCollection
System.CodeDom..::.CodeCommentStatementCollection
System.CodeDom..::.CodeDirectiveCollection
System.CodeDom..::.CodeExpressionCollection
System.CodeDom..::.CodeNamespaceCollection
System.CodeDom..::.CodeParameterDeclarationExpressionCollection
System.CodeDom..::.CodeStatementCollection
System.CodeDom..::.CodeTypeDeclarationCollection
System.CodeDom..::.CodeTypeMemberCollection
System.CodeDom..::.CodeTypeParameterCollection
System.CodeDom..::.CodeTypeReferenceCollection
System.CodeDom.Compiler..::.CompilerErrorCollection
System.ComponentModel.Design.Data..::.DataSourceDescriptorCollection
System.ComponentModel.Design.Data..::.DataSourceGroupCollection
System.ComponentModel.Design..::.DesignerActionItemCollection
System.ComponentModel.Design..::.DesignerActionListCollection
System.ComponentModel.Design..::.DesignerVerbCollection
System.Configuration.Install..::.InstallerCollection
System.Data.SqlClient..::.SqlBulkCopyColumnMappingCollection
System.Diagnostics..::.CounterCreationDataCollection
System.Diagnostics..::.EventLogPermissionEntryCollection
System.Diagnostics..::.PerformanceCounterPermissionEntryCollection
System.DirectoryServices.ActiveDirectory..::.ActiveDirectorySchemaClassCollection
System.DirectoryServices.ActiveDirectory..::.ActiveDirectorySchemaPropertyCollection
System.DirectoryServices.ActiveDirectory..::.ActiveDirectorySiteCollection
System.DirectoryServices.ActiveDirectory..::.ActiveDirectorySiteLinkCollection
System.DirectoryServices.ActiveDirectory..::.ActiveDirectorySubnetCollection
System.DirectoryServices.ActiveDirectory..::.DirectoryServerCollection
System.DirectoryServices..::.DirectoryServicesPermissionEntryCollection
System.DirectoryServices..::.PropertyValueCollection
System.DirectoryServices.Protocols..::.DirectoryAttribute
System.DirectoryServices.Protocols..::.DirectoryAttributeCollection
System.DirectoryServices.Protocols..::.DirectoryAttributeModificationCollection
System.DirectoryServices.Protocols..::.DirectoryControlCollection
System.Messaging..::.AccessControlList
System.Messaging..::.MessageQueuePermissionEntryCollection
System.Security.Cryptography.X509Certificates..::.X509CertificateCollection
System.ServiceProcess..::.ServiceControllerPermissionEntryCollection
System.Web..::.ParserErrorCollection
System.Web.Services.Description..::.BasicProfileViolationCollection
System.Web.Services.Description..::.MimePartCollection
System.Web.Services.Description..::.MimeTextMatchCollection
System.Web.Services.Description..::.ServiceDescriptionBaseCollection
System.Web.Services.Description..::.WebReferenceCollection
System.Web.Services.Discovery..::.DiscoveryClientResultCollection
System.Web.Services.Discovery..::.DiscoveryReferenceCollection
System.Web.Services.Protocols..::.SoapHeaderCollection
System.Web.UI.WebControls..::.EmbeddedMailObjectsCollection
System.Web.UI.WebControls..::.RoleGroupCollection
System.Web.UI.WebControls.WebParts..::.ProxyWebPartConnectionCollection
System.Web.UI.WebControls.WebParts..::.WebPartConnectionCollection
System.Web.UI.WebControls.WebParts..::.WebPartDisplayModeCollection
System.Web.UI.WebControls.WebParts..::.WebPartTransformerCollection
System.Windows.Documents..::.LinkTargetCollection
System.Windows.Forms.Design.Behavior..::.BehaviorServiceAdornerCollection
System.Windows.Forms.Design.Behavior..::.GlyphCollection
System.Xml.Schema..::.XmlSchemaObjectCollection
System.Xml.Serialization.Advanced..::.SchemaImporterExtensionCollection
System.Xml.Serialization..::.XmlAnyElementAttributes
System.Xml.Serialization..::.XmlArrayItemAttributes
System.Xml.Serialization..::.XmlElementAttributes
System.Xml.Serialization..::.XmlSchemas
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 CollectionBase, but derived classes can create their own synchronized versions of the CollectionBase 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.
.NET Framework
Supported in: 3.5, 3.0, 2.0, 1.1, 1.0
.NET Compact Framework
Supported in: 3.5, 2.0, 1.0
XNA Framework
Supported in: 3.0, 2.0, 1.0
Reference
Other Resources