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 Phone 8.1, Windows Phone 8, 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.