ListBox.ObjectCollection.IndexOf Method

Returns the index within the collection of the specified item.

Namespace: System.Windows.Forms
Assembly: System.Windows.Forms (in

public int IndexOf (
	Object value
public final int IndexOf (
	Object value
public final function IndexOf (
	value : Object
) : int



An object representing the item to locate in the collection.

Return Value

The zero-based index where the item is located within the collection; otherwise, negative one (-1).

Exception typeCondition


The value parameter is null.

The IndexOf method enables you to determine where an item is located within the collection. To determine whether an item is located within the collection before calling this method, use the Contains method.

Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

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

.NET Framework

Supported in: 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0