ArrayList.IndexOf Method (Object, Int32, Int32)

.NET Framework (current version)

Note
The .NET API Reference documentation has a new home. Visit the .NET API Browser on docs.microsoft.com to see the new experience.

Searches for the specified Object and returns the zero-based index of the first occurrence within the range of elements in the ArrayList that starts at the specified index and contains the specified number of elements.

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

Syntax

C++

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

Parameters

value: Type: System.Object
The Object to locate in the ArrayList. The value can be null.

startIndex: Type: System.Int32
The zero-based starting index of the search. 0 (zero) is valid in an empty list.

count: Type: System.Int32
The number of elements in the section to search.

Return Value

Type: System.Int32

The zero-based index of the first occurrence of value within the range of elements in the ArrayList that starts at startIndex and contains count number of elements, if found; otherwise, -1.

Exceptions

Exception	Condition
ArgumentOutOfRangeException	startIndex is outside the range of valid indexes for the ArrayList. -or- count is less than zero. -or- startIndex and count do not specify a valid section in the ArrayList.

Remarks

The ArrayList is searched forward starting at startIndex and ending at startIndex plus count minus 1, if count is greater than 0.

This method performs a linear search; therefore, this method is an O(n) operation, where n is count.

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.