Assembly: System.Windows.Forms (in system.windows.forms.dll)
An object representing the item to locate in the collection.
Return ValueThe zero-based index where the item is located within the collection; otherwise, -1.
The value parameter was a null reference (Nothing in Visual Basic).
The IndexOf method enables you to determine where an item is located within the collection. To determine if an item is located within the collection before calling this method, use the Contains method.
Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter EditionThe Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.