Retrieves the index of the first occurrence of the specified item within the collection.
Assembly: System.Windows.Forms (in System.Windows.Forms.dll)
If is called successively, the last returned index will be checked for a key match first, and if there is no match, the search starts at the beginning of the collection.
The key comparison is not case-sensitive. If the key parameter is null or an empty string, or an item with the specified key is not found, returns -1.
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.