ArrayList.GetEnumerator Method (Int32, Int32) (System.Collections)

GetEnumerator Method (Int32, Int32)

.NET Framework Class Library

ArrayList..::.GetEnumerator Method (Int32, Int32)

Returns an enumerator for a range of elements in the ArrayList.

Namespace: System.Collections
Assembly: mscorlib (in mscorlib.dll)

Syntax

Visual Basic (Declaration)

Public Overridable Function GetEnumerator ( _
    index As Integer, _
    count As Integer _
) As IEnumerator

Visual Basic (Usage)

Dim instance As ArrayList
Dim index As Integer
Dim count As Integer
Dim returnValue As IEnumerator

returnValue = instance.GetEnumerator(index, _
    count)

public virtual IEnumerator GetEnumerator(
    int index,
    int count
)

Visual C++

public:
virtual IEnumerator^ GetEnumerator(
    int index, 
    int count
)

JScript

public function GetEnumerator(
    index : int, 
    count : int
) : IEnumerator

Parameters

index: Type: System..::.Int32
The zero-based starting index of the ArrayList section that the enumerator should refer to.

count: Type: System..::.Int32
The number of elements in the ArrayList section that the enumerator should refer to.

Return Value

Type: System.Collections..::.IEnumerator
An IEnumerator for the specified range of elements in the ArrayList.

Exceptions

Exception	Condition
ArgumentOutOfRangeException	index is less than zero. -or- count is less than zero.
ArgumentException	index and count do not specify a valid range in the ArrayList.

Exception

Condition

ArgumentOutOfRangeException

index is less than zero.

-or-

count is less than zero.

ArgumentException

index and count do not specify a valid range in the ArrayList.

Remarks

The foreach statement of the C# language (for each in Visual C++, For Each Visual Basic) hides the complexity of the enumerators. Therefore, using foreach is recommended, instead of directly manipulating the enumerator.

Enumerators can be used to read the data in the collection, but they cannot be used to modify the underlying collection.

Initially, the enumerator is positioned before the first element in the collection. Reset also brings the enumerator back to this position. At this position, Current is undefined. Therefore, you must call MoveNext to advance the enumerator to the first element of the collection before reading the value of Current.

Current returns the same object until either MoveNext or Reset is called. MoveNext sets Current to the next element.

If MoveNext passes the end of the collection, the enumerator is positioned after the last element in the collection and MoveNext returns false. When the enumerator is at this position, subsequent calls to MoveNext also return false. If the last call to MoveNext returned false, Current is undefined. To set Current to the first element of the collection again, you can call Reset followed by MoveNext.

An enumerator remains valid as long as the collection remains unchanged. If changes are made to the collection, such as adding, modifying, or deleting elements, the enumerator is irrecoverably invalidated and its behavior is undefined.

The enumerator does not have exclusive access to the collection; therefore, enumerating through a collection is intrinsically not a thread-safe procedure. To guarantee thread safety during enumeration, you can lock the collection during the entire enumeration. To allow the collection to be accessed by multiple threads for reading and writing, you must implement your own synchronization.

This method is an O(1) operation.

Version Compatibility

In the .NET Framework version 1.0 and 1.1, the enumerator for an ArrayList wrapper returned by the Adapter method treated the second argument as an upper bound rather than as a count. In the .NET Framework 2.0 the second argument is correctly treated as a count.

Platforms

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

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.

Version Information

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

Reference

ArrayList Class

ArrayList Members

GetEnumerator Overload

System.Collections Namespace