CollectionBase Class
Assembly: mscorlib (in mscorlib.dll)
'Declaration <SerializableAttribute> _ <ComVisibleAttribute(True)> _ Public MustInherit Class CollectionBase Implements IList, ICollection, IEnumerable 'Usage Dim instance As CollectionBase
/** @attribute SerializableAttribute() */ /** @attribute ComVisibleAttribute(true) */ public abstract class CollectionBase implements IList, ICollection, IEnumerable
SerializableAttribute ComVisibleAttribute(true) public abstract class CollectionBase implements IList, ICollection, IEnumerable
Not applicable.
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
import System.* ;
import System.Collections.*;
import System.Collections.CollectionBase.*;
public class Int16Collection extends CollectionBase
{
/** @property
*/
public short get_Value(int index)
{
short s = System.Convert.ToInt16(get_List().get_Item(index));
return(s) ;
} //get_Value
/** @property
*/
public void set_Value(int index,short value)
{
get_List().set_Item(index, (Int16)value);
} //set_Value
public int Add(short value)
{
return get_List().Add((Int16)value);
} //Add
public int IndexOf(short value)
{
return get_List().IndexOf((Int16)value);
} //IndexOf
public void Insert(int index, short value)
{
get_List().Insert(index, (Int16)value);
} //Insert
public void Remove(short value)
{
get_List().Remove((Int16)value);
} //Remove
public boolean Contains(short value)
{
// If value is not of type Int16, this will return false.
return get_List().Contains((Int16)value);
} //Contains
protected void OnInsert(int index, Object value)
{
// Insert additional code to be run only when inserting values.
} //OnInsert
protected void OnRemove(int index, Object value)
{
// Insert additional code to be run only when removing values.
} //OnRemove
protected void OnSet(int index, Object oldValue, Object newValue)
{
// Insert additional code to be run only when setting values.
} //OnSet
protected void OnValidate(Object value)
{
if ( value.GetType() != Type.GetType("System.Int16") ) {
throw new ArgumentException("value must be of type Int16.",
"value");
}
} //OnValidate
} //Int16Collection
public class SamplesCollectionBase
{
public static void main(String[] args)
{
// 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 for.
Console.WriteLine("Contents of the collection (using for):");
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}",
(System.Boolean)myI16.Contains((Int16)3));
Console.WriteLine("2 is at index {0}.",
(Int16)myI16.IndexOf((Int16)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 .set_Item( 4 ,(Int16)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);
} //main
// Uses the Count property and the Item property.
public static void PrintIndexAndValues(Int16Collection myCol)
{
for(int i = 0; i < myCol.get_Count(); i++) {
Console.WriteLine(" [{0}]: {1}", (Int32)i,
myCol.get_Item(i));
}
Console.WriteLine();
} //PrintIndexAndValues
// Uses the for statement which hides the complexity of the enumerator.
// NOTE: The for statement is the preferred way of enumerating the contents
// of a collection.
public static void PrintValues1(Int16Collection myCol)
{
for (int iCtr = 0; iCtr < myCol.get_Count(); iCtr++) {
Console.WriteLine(" {0}", myCol.get_Item(iCtr));
}
Console.WriteLine();
} //PrintValues1
// Uses the enumerator.
// NOTE: The for 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.get_Current());
}
Console.WriteLine();
} //PrintValues2
} //SamplesCollectionBase
/*
Contents of the collection (using for):
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
*/
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 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.