ArrayList.IndexOf Method (Object, Int32)

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

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

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

Parameters

value
Type: System.Object

The Object to locate in the ArrayList. The value can be a null reference (Nothing in Visual Basic).

startIndex
Type: System.Int32

The zero-based starting index of the search. 0 (zero) is valid in an empty list.

Return Value

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

ExceptionCondition
ArgumentOutOfRangeException

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

The ArrayList is searched forward starting at startIndex and ending at the last element.

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

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 first occurrence of a specified element.

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

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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

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