CollectionBase Class
Provides the abstract base class for a strongly typed collection.
Assembly: mscorlib (in mscorlib.dll)
System.Collections.CollectionBase
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
| Name | Description | |
|---|---|---|
![]() | CollectionBase() | Initializes a new instance of the CollectionBase class with the default initial capacity. |
![]() | CollectionBase(Int32) | Initializes a new instance of the CollectionBase class with the specified capacity. |
| Name | Description | |
|---|---|---|
![]() | Capacity | Gets or sets the number of elements that the CollectionBase can contain. |
![]() | Count | Gets the number of elements contained in the CollectionBase instance. This property cannot be overridden. |
![]() | InnerList | Gets an ArrayList containing the list of elements in the CollectionBase instance. |
![]() | List | Gets an IList containing the list of elements in the CollectionBase instance. |
| Name | Description | |
|---|---|---|
![]() | Clear() | Removes all objects from the CollectionBase instance. This method cannot be overridden. |
![]() | Equals(Object) | Determines whether the specified object is equal to the current object.(Inherited from Object.) |
![]() | Finalize() | Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.(Inherited from Object.) |
![]() | GetEnumerator() | Returns an enumerator that iterates through the CollectionBase instance. |
![]() | GetHashCode() | Serves as the default hash function. (Inherited from Object.) |
![]() | GetType() | |
![]() | MemberwiseClone() | |
![]() | OnClear() | Performs additional custom processes when clearing the contents of the CollectionBase instance. |
![]() | OnClearComplete() | Performs additional custom processes after clearing the contents of the CollectionBase instance. |
![]() | OnInsert(Int32, Object) | Performs additional custom processes before inserting a new element into the CollectionBase instance. |
![]() | OnInsertComplete(Int32, Object) | Performs additional custom processes after inserting a new element into the CollectionBase instance. |
![]() | OnRemove(Int32, Object) | Performs additional custom processes when removing an element from the CollectionBase instance. |
![]() | OnRemoveComplete(Int32, Object) | Performs additional custom processes after removing an element from the CollectionBase instance. |
![]() | OnSet(Int32, Object, Object) | Performs additional custom processes before setting a value in the CollectionBase instance. |
![]() | OnSetComplete(Int32, Object, Object) | Performs additional custom processes after setting a value in the CollectionBase instance. |
![]() | OnValidate(Object) | Performs additional custom processes when validating a value. |
![]() | RemoveAt(Int32) | Removes the element at the specified index of the CollectionBase instance. This method is not overridable. |
![]() | ToString() | Returns a string that represents the current object.(Inherited from Object.) |
| Name | Description | |
|---|---|---|
![]() ![]() | ICollection.CopyTo(Array, Int32) | Copies the entire CollectionBase to a compatible one-dimensional Array, starting at the specified index of the target array. |
![]() ![]() | IList.Add(Object) | Adds an object to the end of the CollectionBase. |
![]() ![]() | IList.Contains(Object) | Determines whether the CollectionBase contains a specific element. |
![]() ![]() | IList.IndexOf(Object) | Searches for the specified Object and returns the zero-based index of the first occurrence within the entire CollectionBase. |
![]() ![]() | IList.Insert(Int32, Object) | Inserts an element into the CollectionBase at the specified index. |
![]() ![]() | IList.Remove(Object) | Removes the first occurrence of a specific object from the CollectionBase. |
![]() ![]() | ICollection.IsSynchronized | Gets a value indicating whether access to the CollectionBase is synchronized (thread safe). |
![]() ![]() | ICollection.SyncRoot | Gets an object that can be used to synchronize access to the CollectionBase. |
![]() ![]() | IList.IsFixedSize | Gets a value indicating whether the CollectionBase has a fixed size. |
![]() ![]() | IList.IsReadOnly | Gets a value indicating whether the CollectionBase is read-only. |
![]() ![]() | IList.Item(Int32) | Gets or sets the element at the specified index. |
| Name | Description | |
|---|---|---|
![]() | AsParallel() | Overloaded. Enables parallelization of a query.(Defined by ParallelEnumerable.) |
![]() | AsQueryable() | Overloaded. Converts an IEnumerable to an IQueryable.(Defined by Queryable.) |
![]() | Cast(Of TResult)() | Casts the elements of an IEnumerable to the specified type.(Defined by Enumerable.) |
![]() | OfType(Of TResult)() | Filters the elements of an IEnumerable based on a specified type.(Defined by Enumerable.) |
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
Available since 10
.NET Framework
Available since 1.1
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.






