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ArrayList.LastIndexOf Method (Object, Int32)

Searches for the specified Object and returns the zero-based index of the last occurrence within the range of elements in the ArrayList that extends from the first element to the specified index.

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

abstract LastIndexOf : 
        value:Object * 
        startIndex:int -> int 
override LastIndexOf : 
        value:Object * 
        startIndex:int -> int 


Type: System.Object
The Object to locate in the ArrayList. The value can be a null reference (Nothing in Visual Basic).
Type: System.Int32
The zero-based starting index of the backward search.

Return Value

Type: System.Int32
The zero-based index of the last occurrence of value within the range of elements in the ArrayList that extends from the first element to startIndex, if found; otherwise, -1.


startIndex is outside the range of valid indexes for the ArrayList.

The ArrayList is searched backward starting at startIndex and ending at the first element.

This method performs a linear search; therefore, this method is an O(n) operation, where n is the number of elements from the beginning of the ArrayList to startIndex.

This method determines equality by calling Object.Equals.

Starting with the .NET Framework 2.0, this method uses the collection’s objects’ Equals and CompareTo methods on item to determine whether item exists. In the earlier versions of the .NET Framework, this determination was made by using the Equals and CompareTo methods of the item parameter on the objects in the collection.

The following code example shows how to determine the index of the last occurrence of a specified element.

No code example is currently available or this language may not be supported.

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.