Setting this property on a server control provides you with programmatic access to the server control's properties, events, and methods. This property can be set by Web developers by declaring an ID attribute in the opening tag of an ASP.NET server control.
If this property is not specified for a server control, either declaratively or programmatically, you can obtain a reference to the control through its parent control's Controls property.
Only combinations of alphanumeric characters and the underscore character ( _ ) are valid values for this property. Including spaces or other invalid characters will cause an ASP.NET page parser error.
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)